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Welcome to Google Earth! Once you download and install Google Earth,
your computer becomes a window to anywhere on the planet, allowing you to view high-resolution aerial and satellite imagery, elevation terrain, road and street labels, business listings, and more. System Requirements To use Google Earth on a Windows PC, you must have at least the following: l Operating System: Windows 2000, Windows XP l CPU: 500Mhz, Pentium 3 l System Memory (RAM): 128MB RAM l Hard Disk: 400MB free space l Network Speed: 128 Kbits/sec l Graphics Card: 3D-capable with 16MB of VRAM l Screen: 1024x768, "16-bit High Color" screen Hacking Google® Maps and Google® Earth LIMIT OF LIABILITY/DISCLAIMER OF WARRANTY: THE PUBLISHER AND THE AUTHOR MAKE NO REPRESENTATIONS OR WARRANTIES WITH RESPECT TO THE ACCURACY OR COMPLETENESS OF THE CONTENTS OF THIS WORK AND SPECIFICALLY DISCLAIM ALL WARRANTIES, INCLUDING WITHOUT LIMITATION WARRANTIES OF FITNESS FOR A PARTICULAR PURPOSE. NO WARRANTY MAY BE CREATED OR EXTENDED BY SALES OR PROMOTIONAL MATERIALS. THE ADVICE AND STRATEGIES CONTAINED HEREIN MAY NOT BE SUITABLE FOR EVERY SITUATION.THIS WORK IS SOLD WITH THE UNDERSTANDING THAT THE PUBLISHER IS NOT ENGAGED IN RENDERING LEGAL, ACCOUNTING, OR OTHER PROFESSIONAL SERVICES. IF PROFESSIONAL ASSISTANCE IS REQUIRED, THE SERVICES OF A COMPETENT PROFESSIONAL PERSON SHOULD BE SOUGHT. NEITHER THE PUBLISHER NOR THE AUTHOR SHALL BE LIABLE FOR DAMAGES ARISING HEREFROM. THE FACT THAT AN ORGANIZATION OR WEBSITE IS REFERRED TO IN THIS WORK AS A CITATION AND/OR A POTENTIAL SOURCE OF FURTHER INFORMATION DOES NOT MEAN THAT THE AUTHOR OR THE PUBLISHER ENDORSES THE INFORMATION THE ORGANIZATION OR WEBSITE MAY PROVIDE OR RECOMMENDATIONS IT MAY MAKE. FURTHER, READERS SHOULD BE AWARE THAT INTERNET WEBSITES LISTED IN THIS WORK MAY HAVE CHANGED OR DISAPPEARED BETWEEN WHEN THIS WORK WAS WRITTEN AND WHEN IT IS READ. Introducing Google Earth All of the preceding chapters focused on the Google Maps API. The Google Maps system provides a browser-based interface to the data in the Google database, both in terms of the map and the satellite photos. The API provides the ultimate in flexibility for building and incorporating Google Maps data into web-based applications. That flexibility, however, comes at the potential price of limiting the environment and interface. Even with the flexibility of the JavaScript language and the ability to create and organize content in ways that suit the application, you can add additional layers of data to the map information already demonstrated. In particular, the web-based Google Maps interface is incapable of providing the interaction and display of three-dimensional data. The limitations extend not only to the base data, but also to the information that you can overlay on the map. Google Earth, on the other hand, has no restrictions on the interface and how the user interacts with the Google Earth data. Google Earth is a desktop application available for Windows and Mac OS X that enables you to browse Google Earth images in a more dynamic environment. Using Google Earth you move about the earth in 3D, moving and manipulating the Google Earth data in real time. This provides additional information that would be difficult to represent within the Google Maps interface, such as “tilting” the earth so that you can see the relative height of different areas of land. This chapter looks at ways in which you can use Google Earth and how to create some basic data to be used within the application to extend the information and functionality of the application. Google Earth Overview The most critical difference between Google Maps and Google Earth is the environment. Google Earth is a standalone application that is available for a limited number of platforms. It is designed as an earth browser for showing satellite images of the earth’s surface in an interactive, 3D environment. The satellite images and the backup data (such as local businesses) in Google Earth are the same as those in Google Maps in satellite mode. The difference is in the way in which the information can be viewed and manipulated. ˛ Google Earth overview ˛ Google Earth overlays ˛ KML for extending Google Earth chapter in this chapter 294 Part IV — Google Earth Hacks Obtaining the Application Google Earth can be downloaded from the Google Earth homepage (http://earth .google.com). There are three versions of the Google Earth application: Google Earth is free for personal use and incorporates satellite images that cover the entire surface of the earth. The free client also provides access to all of the different Google Local–supported databases, including those that provide information about locations, local businesses, and route finding. Google Earth also incorporates the technology for generating and representing information based on the Keyhole Markup Language (KML). This is the version that is described throughout the rest of this chapter. Google Earth Plus is an optional (and low-cost) upgrade to the free client that extends the functionality of Google Earth to include interfaces to GPS devices, higher resolution for printed images (higher than onscreen), extended annotation and drawing tools, and a data importer that will read files in CSV format. Google Earth Plus is supported only on Windows (at the time of writing). Google Earth Pro is a professional product and is therefore significantly more expensive than the Google Earth Plus upgrade. It incorporates much faster download times and data streaming, extended layers and overlay support, and improvements to the annotation system that enable you to develop much more detailed overlays directly within the Google Earth application. Google Earth Pro is supported only on Windows (at the time of writing). Google Earth Pro also supports a number of extension modules, including those for making movies (by “flying” through the Google Earth data), a high-resolution printing module, and data modules providing traffic and shopping data. For all three applications, Google Earth is merely the desktop interface to the data on the Google Earth servers. You must first download the client that enables you to view and interact with the data. Then you can connect to the Internet to obtain and download the images that are displayed onscreen. There is a fourth Google Earth application, Google Earth Enterprise, which is designed to provide Google Earth features in combination with heavily customized information within an enterprise environment. Google Earth Enterprise is technically a range of applications that work together to provide Google Earth data, combined with your own enterprise information, such as statistical and customer data. For more information see the Google Earth Enterprise web site at http:// earth.google.com/earth_enterprise.html. Google Earth Features The Google Earth application provides an interface to the Google satellite imagery, and because it is not limited by the interface available through a web browser and JavaScript, there is a lot more flexibility and interactivity in the Google Earth application. Some of the key differences are detailed shortly. First, examine Figure 15-1, which shows the basic interface of the Google Earth application. Chapter 15 — Introducing Google Earth 295 FIGURE 15-1: The basic interface. The interface is divided into three panels. The panel on the left provides the data points, overlays, and search interface that enable you to add data and move around the map using town, city, and other information point references. The panel at the bottom of the application window provides an interface for moving and working around the earth. The larger, main panel is the window to the Google Earth satellite imagery. Core Functionality The fundamental difference between Google Maps and Google Earth is the way in which the satellite imagery can be viewed and manipulated. The satellite images are the same as Google Maps, but the way in which the data is displayed differs in that it is slightly more fluid than the Google Maps interface. For example, the default start position is high above the United States.With Google Earth, you can tell exactly how high. The information immediately beneath the Google Earth image provides, from left to right: 296 Part IV — Google Earth Hacks The longitude/latitude of the current center point of the map (called the Pointer). The elevation (height above sea level) of that point. The status of the information satellite images that are streamed to the application. The altitude of the current view; that is, the height (above sea level) from which you see information. You can see, from Figure 15-1, just how high up you would have to be to see the same information. If you double-click one of the points on the left, say, the Google Campus, you will “fly” to the Google Campus, with the satellite imagery flowing past, until the map centers on the Google Campus. This is almost impossible to represent within a book, but Figures 15-2 through 15-4 show some interstitial images from the starting point in Figure 15-1 to give you some idea. FIGURE 15-2: Starting the flight. Chapter 15 — Introducing Google Earth 297 FIGURE 15-3: Almost there. FIGURE 15-4: The Google Campus. 298 Part IV — Google Earth Hacks At no time are areas of the map missing while Google Earth loads the satellite image data. Instead Google Earth streams the necessary information from Google’s servers to gradually load the image data as you zoom in through different levels. This sequence is automatic and much more visual than even the panning option provided within the Google Maps interface.To manually move around the map, a number of options are available: Click and drag: The same basic method as available within Google Maps. Click anywhere on the map, drag the map in the direction you want, and then release the mouse. You will move to the new location. Cursor keys: The standard cursor keys on your keyboard move the map in the direction you choose. Joystick: There is a built in “joystick” in the center of the control panel on the map. Clicking the different arrows on the joystick moves the map. Click and move: If you click the mouse and move the map quickly and then release, the map will begin to scroll in the direction you moved the mouse.To stop the scrolling, click the red button in the middle of the joystick or click once on the map with the mouse. By default, your map will always be oriented to face north. You can rotate the map using the two buttons to the top left and right of the joystick, which rotate the map counterclockwise and clockwise. You can always tell the current orientation by using the built-in compass shown in the bottom left of the map panel. You can reset it using the “N” button on the bottom left. Finally, you can zoom in and out of the map using the slider on the left, or, if your mouse has a scroll wheel, using the scroll wheel to zoom out (roll forward) and in (roll back). Simple Overlays Numerous built-in overlays are provided with the application.To see them in action, move to Seattle by typing Seattle into the search box and clicking the search button. You should get a window like the one shown in Figure 15-5. From the Layers panel on the left, select “Crime Stats” and then zoom out slightly and you’ll see the crime statistics for 2000 for a number of counties across the Seattle region, as shown in Figure 15-6. Chapter 15 — Introducing Google Earth 299 FIGURE 15-5: Seattle. FIGURE 15-6: Crime statistics in Seattle. 300 Part IV — Google Earth Hacks Each icon is an example of a data point, the equivalent of the GMarker object used in the Google Maps to highlight a single point on the map. Points of Interest In addition to locating the key points on the map, you can also overlay and move to key points of interest on the map. The Google headquarters was an example of this, and a huge number of other examples exist throughout the Google Maps application. There is no point in listing those examples here; they are far too numerous and constantly updating. Much of the content is U.S.-centric at the moment, but more data is being added all the time. You can add as many of these overlays to the map as you like. There is no limit, although the application will slow down as you add more and more points and overlays to the map. The data and overlay information can be extensive and interesting. For example, Figure 15-7 shows the airports and train stations in Seattle. FIGURE 15-7: Adding airport and train station data. Routes and Paths Searches for information and locations work just the same as they do within Google Maps. You can move directly to an address and also find routes between two different points. If all you want to see is an overlay of the roads, select the “roads” overlay from the Layers panel. This provides a view similar to the Hybrid view in Google Maps, where roads are overlaid directly on top of the satellite imagery. You can see this more clearly in Figure 15-8, where the roads overlay has been added to the southern tip of Manhattan Island. Chapter 15 — Introducing Google Earth 301 FIGURE 15-8: Roads in Google Earth. Just as with Google Local, you can determine a route’s two points by searching for the first point and using the pop-up panel to select the destination. Figure 15-9 shows a route between Ambleside and Whitehaven in the Lake District in the U.K. So far the routing shows nothing different from what you might expect within Google Maps. There is, however, a slightly different view of the route available within Google Earth. Terrain and Altitude Google Earth includes altitude information for the whole of the earth. This means that you can get a fairly accurate idea of the altitude of a particular point within Google Earth. Google has, however, gone one stage further and provided the ability to display this information interactively on the map. If you select the Terrain checkbox in the bottom left of the control panel, the view of the map adjusts slightly, but probably imperceptibly. But, change the attitude (or tilt) of your view, and the difference becomes obvious.To adjust the tilt, use the slider on the right of the joystick in the control panel. Moving the slider down tilts the map so that the top of the view rotates horizontally, moving your perspective closer to the ground. Moving the slider up rotates the map up. 302 Part IV — Google Earth Hacks FIGURE 15-9: Ambleside to Whitehaven in Google Earth. The result is dramatic. You can see the altitude of the different areas of the map and the route, and Google Earth now shows the route winding through some of the lower-lying mountains in the Lake District (see Figure 15-10). For another dramatic representation, try going to Sorrento. I visited Sorrento for a conference and was immediately struck by the nearby mountains, which seemed to dominate the skyline more than Vesuvius, a much more well-known entity on the beautiful coastline of Naples. The mountains to the right of Sorrento (as you look northeast) came as a complete surprise by the time I arrived at the hotel.What I should have done, of course, is quickly check Google Earth to see the lay of the land, as shown in Figure 15-11, which shows the mountains immediately to the right and behind the hotel. Vesuvius cannot be seen in this shot, but is immediately to the left of the view shown here. Chapter 15 — Introducing Google Earth 303 FIGURE 15-10: Ambleside to Whitehaven with altitude. FIGURE 15-11: Sorrento and mountains. 304 Part IV — Google Earth Hacks Buildings The geological aspects of Google Earth are of course important, but man has had a significant impact on how different locations around the world appear because of the buildings and structures that he has created. For completeness, Google Earth includes some man-made structures in the Google Earth map. If you visit Seattle and click the Buildings checkbox, Google Earth displays the various buildings in Seattle on the map (see Figure 15-12). FIGURE 15-12: Buildings in Seattle in Google Earth. The result shows one of the effects we experienced: the apparent lack of very tall skyscrapers, which helps give the wonderful impression of space and open-air feel that we discovered in Seattle compared to New York. Extending Google Earth Information Earlier in this chapter, you saw the information that can be built and overlaid within Google Earth. Google Earth obviously comes with its own massive library of data, information points, and highlights that can be overlaid on the map. All of this information is provided through a series of data files that are in the Keyhole Markup Language (KML) standard. KML is a specialized type of XML that enables you to build and organize points, routes, and other information. Chapter 15 — Introducing Google Earth 305 The format of the data is not very difficult to understand or generate. Many of the principles that have been used through the rest of the book, such as specifying the latitude and longitude of a point and adding icons and other data, should be familiar. Unlike Google Maps, where the applications that build and overlay this information on the map had to be encoded, the extension method within Google Earth is provided entirely within the structure and format of the KML files. This section looks at some of the basics of the KML system. Exporting Your Tags The easiest way to generate and share points, routes, and other data within Google Earth is to save the points you find and put them into your My Places folder (or another folder you create). You can then save the folder contents into a KML or KMZ file (a Zipped version of a KML file) that you can then share with other people by simply distributing the file. You can see the result of the KML file generated during the earlier examples here: Seattle, WA, USA New York, NY, USA Ambleside, LA22, UK 306 Part IV — Google Earth Hacks Ben Nevis, UK Seattle, WA, USA The structure and content of the file is, as you can see, very simple and doesn’t differ in many respects from some of the XML documents that you used in examples earlier in this book. Basic KML Principles The KML standard is huge. Google’s own documentation on KML is almost 120 pages, and the contents are not going to be reproduced here. Instead, look at the highlights and key points, starting with the basic format of a KML file. The basis of the KML file structure is as follows: The main KML XML root tag. The Document tag defines the content of the document (and contains global document information and a number of folders). The Folder tag defines the contents of a single folder, with each folder containing the details of one or more placemarks, routes, or other structures. Chapter 15 — Introducing Google Earth 307 Within a folder, you add placemarks, and these are composed of further elements and definitions that describe the placemark and its components. Placemarks The placemark is the primary method of highlighting information within a Google Earth KML document. A placemark is a single entity within the Google Earth application and can refer to a single point, a line, a route, a polygon, or any combination of these. For example, a placemark could be your house, or it could be a re-creation of the stones at Stonehenge. Both are single entities but are composed of one and many points and coordinates, respectively. The points that you define as part of a placemark can consist not just of the latitude and longitude, but also the altitude and even the relationship between the ground and your point on the map. You can also add a custom icon to the placemark (just as with a GMarker in Google Maps). Finally, you can control the appearance of the placemark, from the display text and information panel to the name, style, and color of the label. You can also set the camera “view,” that is, the location, altitude, direction, and tilt of the map when the user selects the placemark. Geometry Google Earth provides the ability to draw single points, lines, and polygons onto the map. All geometry types consist of the coordinates (latitude, longitude), altitude, enabling points, lines, and polygons to appear either on the ground or in the air. Coordinates are specified using the coordinates tag, specifying the longitude, latitude, and altitude in that order. Hence, you can find Sorrento using the KML: All coordinates can be given a color, and polygons can be transparent (only their lines are drawn) or solid (enabling you to construct buildings and other elements). All points, lines, and polygons can be extruded; their location can be linked to another location. For example, you can tether a coordinate to the ground even though it is displayed in the air. For absolute flexibility you can group points, lines, and polygons into a collection, which in turn can be used to describe single elements. For example, when constructing a building, you could group the polygons that make up the building into a collection. Overlays Images can be overlaid on the map.Two types are available: a ground overlay and a screen overlay. Ground overlays ping the image to specific areas on the ground of the map. Screen overlays enable you to “float” information in the Google Earth display. The overlay image can be a JPG, PNG, GIF, or TIFF. You can either make the image available over the Internet (or other network) or embed the image into a KMZ file along with the KML file that uses it. 308 Part IV — Google Earth Hacks Wrapping Up The Google Earth application provides a different environment for viewing the Google satellite images in a method that also adds additional layers of information, such as terrain and 3D buildings. The information displayed is the same as Google Maps, but the methods that are available to extend the Google Earth application are different and rely on an XML-based format called KML. KML is limited to providing additional data points for overlaying on top of the Google Earth data. There is little of the interactivity provided within Google Maps and the browser, but the Google Earth application provides a richer environment for displaying some types of data. Now that you know the basics of Google Earth and what the KML format is capable of, you can examine some samples of overlays that use the data generated in the previous Google Maps examples, but using the KML format in Google Earth. Generating Google Earth Feeds With Google Maps, the JavaScript language and Google Maps object environment were required to build the marker and then overlay the marker onto the Google Map. Google Earth provides a much simpler method for adding points of interest to the map.With Google Earth, the Google Earth application does all of the overlay legwork. All you need to do is create a suitable KML file that provides the bare structure and coordinates of the point you want to highlight. Because there is no programming involved, the structure and content of the KML file is critical. This chapter describes the basics of the KML file format required for a basic point, along with some extensions and examples of dynamism that can be added to the system. Showing Points The basic KML point is the of this in the previous chapter, but the structure is quite straightforward. Only two components are required for a the point (containing coordinates for latitude/longitude) to which the point refers. You can also add further information, such as the tag, icons, and further descriptive data to the your needs. For example, here’s a small Yorkshire Bank in Grantham: 10 High St,Grantham, NG31 6PU, United Kingdom The the point, in that order, separated by a comma. ˛ Create KML placemarks ˛ Update KML dynamically ˛ Link to networks chapter in this chapter 310 Part IV — Google Earth Hacks Generating KML from Existing Data To demonstrate how easy it is to create a KML document with appropriate information, you can adapt the data that was generated for the database in Chapter 11 (local Grantham businesses) and instead generate a KML document. To generate the information, you follow the same basic method as in Chapter 11 to generate the XML that was previously parsed by JavaScript. Unlike the Google Maps example, where the XML was loaded on a business type-by-type basis, you can dump the entire database and organize the information automatically by type by using the Google Earth folder system. The Google Earth application can handle the filtering and selection process. The KML document defines one set of data and therefore has only one folder in it.To further subdivide information you have to add subfolders. The result is a KML file structure that looks like this: Grantham Business Folder ■ Banks ■ Pharmacies ■ Restaurant ■ Sports ■ Travel The Perl script for generating the file is as follows: #!/usr/bin/perl use DBI; use strict; my $dbh = DBI->connect( ‘dbi:mysql:database=mapsbookex;host=db.maps.mcslp.com’, ‘mapsbookex’, ‘examples’, ); You start with the opening structure. The contents should be displayed when the file is first opened within Google Earth: print< EOF The SQL statement picks all available options but orders the information by type so that the individual folders can be created: Chapter 16 — Generating Google Earth Feeds 311 my $sth = $dbh->prepare(sprintf(‘select * from ch10 order by type’)); $sth->execute(); To generate the individual structure. The $currenttype variable is used to identify first the current type so that you can determine whether to create a new folder. The $count variable is used to identify the count to determine whether the closing tag needs to be created (for the first change of type, it doesn’t). Note that for the subfolders, you don’t open the contents; this doesn’t affect whether the enclosed points are displayed, only whether the list of points in the folder is displayed: my ($currenttype,$count) = (‘’,0); while (my $row = $sth->fetchrow_hashref()) { if ($currenttype ne $row->{type}) { if ($count > 0) { print “ } printf(“ $currenttype = $row->{type}; } $count++; Each individual placemark is composed of the name, coordinates, and address of each entity in the database: printf(“ \n \n $row->{title}, $row->{adda}, $row->{addb}, $row->{lng}, $row->{lat}, ); } $sth->finish(); Finally, you close the last entity type folder, the global KML folder, and finally the KML document itself: print(“ Using the information that is in the final version of the database created in Chapter 11, the preceding script generates the following KML. The quantity of KML included here is shown to provide an overview of the overall structure, as well as the individual points. Even so, the document has been shortened for inclusion in the book. 312 Part IV — Google Earth Hacks The code for this chapter (and all chapters of the book) is available on the web site that accompanies the book, http://maps.mcslp.com. 10 High St,Grantham, NG31 6PU, United Kingdom 1 St. Peters Hill,Grantham, NG31 6QB, United ; Kingdom 88 Westgate,Grantham, NG31 6LF, United ; Kingdom 42 St. Peters Hill,Grantham, NG31 6QF, United ; Kingdom 34 St. Peters Hill,Grantham, NG31 6QF, United ; Kingdom Chapter 16 — Generating Google Earth Feeds 313 ... 8-9 Westgate,Grantham, NG31 6LT, United ; Kingdom 99 Westgate,Grantham, NG31 6LE, United ; Kingdom 50 East St,Grantham, NG31 6QJ, United Kingdom 99 Westgate,Grantham, NG31 6LE, United ; Kingdom If you save the file (for example, using redirection) and then open the file within Google Earth (by selecting File➔Open), you get a window similar to the one shown in Figure 16-1. You can see that Google Earth has zoomed to a point that shows all the loaded tags. You can also see, in the panel on the left, that the folders you created within the KML are displayed. Unlike Google Maps, where individual business types had to be enabled and disabled through a JavaScript function you created, Google Earth now handles the selection process for you. Figure 16-2 shows just banks and restaurants displayed on the map. Of course, generating a static file and distributing it is not particularly efficient, especially if the data changes frequently. 314 Part IV — Google Earth Hacks FIGURE 16-1: Opening the Chapter 11 KML information. FIGURE 16-2: Selecting folders for display. Chapter 16 — Generating Google Earth Feeds 315 Generating KML Dynamically The static KML file generation shown in the previous section is less than ideal when the data changes regularly. For static elements, such as documenting the location of mountains or seas, the information displayed is unlikely to change. For business details, the information is likely to change at least monthly. With some applications, you might want to update the information even more frequently than that. For the moment, you’ll just handle the dynamic generation of information and how that can be loaded into the Google Earth application. Changing the Script To generate the information dynamically, a similar change to that used when moving from the static XML to dynamic XML system used in Chapters 9 and 10 for Google Maps applications is required. The change comes down to a single line: The correct HTTP header and content type must be output by the script. Google Earth supports two file types: KML and KMZ. The former, the uncompressed version, requires the following content type: application/vnd.google-earth.kml+xml xml For KMZ files use the following content type: application/vnd.google-earth.kmz kmz The script will be generating KML, so the change is very straightforward. The entire script is included here for reference to show that there are no differences between this and the static generation version: #!/usr/bin/perl use DBI; use strict; use CGI qw/:standard/; print header(-type => ‘application/vnd.google-earth.kml+xml xml’); my $dbh = DBI->connect( ‘dbi:mysql:database=mapsbookex;host=db.maps.mcslp.com’, ‘mapsbookex’, ‘examples’, ); print< EOF 316 Part IV — Google Earth Hacks my $sth = $dbh->prepare(sprintf(‘select * from ch10 order by type’)); $sth->execute(); my ($currenttype,$count) = (‘’,0); while (my $row = $sth->fetchrow_hashref()) { if ($currenttype ne $row->{type}) { if ($count > 0) { print “ } printf(“ {type})); $currenttype = $row->{type}; } $count++; printf(“ \n $row->{title}, $row->{adda}, $row->{addb}, $row->{lng}, $row->{lat}, ); } $sth->finish(); print(“ Although not demonstrated in this script, error handling with dynamic KML files is very strict, because Google Earth refuses to use the network link if the file is not valid. Therefore, all dynamic KML generators should always return an HTTP response of 200.To show an error, generate the appropriate KML, for example: Care should be taken to ensure you follow this approach. Chapter 16 — Generating Google Earth Feeds 317 Subscribing to a Network Resource The CGI method shown in the previous section generates the necessary KML with the correct headers and structure. However, you need to load the file within Google Earth using a specific option so that that the KML is requested from the URL, rather than loaded from a file. To add a network resource to your Google Earth application, you choose Network Link from the Add menu in Google Earth. You are presented with a window like the one shown in Figure 16-3. FIGURE 16-3: Opening Network resources in Google Earth. Give the Network Link a name. In the Location field, provide the URL of the CGI script that generates the KML.To use the previously detailed example script, use the URL http:// maps.mcslp.com/examples/ch16-02.cgi. You should get a Google Earth display like the one in Figure 16-4. 318 Part IV — Google Earth Hacks FIGURE 16-4: Viewing the dynamic Grantham entities. Here you can see that the resulting folder structure is more or less identical to that produced using the static option. The difference is that the information is being loaded from KML that has been generated dynamically. Now the database can be updated and the Google Earth application can load the updates. The information is manually refreshed when you open the application, when you re-select the Network Link, or when you specifically request a refresh by right-clicking the Network Link and selecting Refresh. Using the Auto-Update Function The network source for KML can be further enhanced by enabling the auto-update function. Using this option, the network KML source is regularly reloaded at an interval that you can specify.To demonstrate this functionality in action, first change the Grantham network resource to automatically reload at specific intervals. Right-click the link generated in the previous option and select Edit. You should see the window in Figure 16-5. Click the checkbox for Refresh Parameters and then set the parameters. You can specify that the refresh occurs at specified intervals or when the view changes (including setting a delay after the view has changed). Within the book, it’s difficult to demonstrate this in perfect action, but you can see some simple changes. First, see Figure 16-6, which shows Google Earth and the dynamic KML in its initial state. Refresh has been set for every five minutes. Chapter 16 — Generating Google Earth Feeds 319 FIGURE 16-5: Setting refresh options. FIGURE 16-6: Dynamic KML. 320 Part IV — Google Earth Hacks Using the script in Chapter 11 that adds new entities to the database, Saddler’s, Shoe Shops, and Stationers have been added to the database. Figure 16-7 shows the new changes after the automatic reload. FIGURE 16-7: Automatic reload of KML data. In this example, the data is unlikely to be reloaded and regenerated so regularly, but the refresh system can be used to help regenerate all sorts of information. For example, KML could be generated to show the current location of an aircraft or a team on an expedition. Each reload would update the position accordingly. Creating a Self-Reloading KML File Not only can this be controlled from within the Google Earth application, but you can set the refresh parameters from within a KML file. You cannot set it in the file that you generate, but you can instead generate a static KML file that refers to the dynamic KML file and includes the refresh parameters. Following is a sample of the KML file, designed to refresh the dynamic example: Chapter 16 — Generating Google Earth Feeds 321 Looking at the individual elements, you can pick out the main points. First, you define the name of the network link: Then you specify the URL, the refresh mode, the interval (specified in seconds), and the viewing format. Open the KML file in Google Earth, and the dynamic KML will automatically be loaded. Adding Icons You can stylize a Style element enables you to set custom styles for a element defines the icon details. For example: The is the same as that used for the Bank icon example demonstrated in Chapter 11. You can use a single source file for the icon and extract the icon using the x/y reference of the left/bottom edge and the height and width of the icon (using the For the final example, you’ll use a simple icon, chosen using the type name to generate the icon, just as used in Chapter 11. The resulting script is shown as follows: 322 Part IV — Google Earth Hacks #!/usr/bin/perl use DBI; use strict; use CGI qw/:standard/; print header(-type => ‘application/vnd.google-earth.kml+xml xml’); my $dbh = DBI->connect( ‘dbi:mysql:database=mapsbookex;host=db.maps.mcslp.com’, ‘mapsbookex’, ‘examples’, ); print< EOF my $sth = $dbh->prepare(sprintf(‘select * from ch10 order by type’)); $sth->execute(); my ($currenttype,$count) = (‘’,0); while (my $row = $sth->fetchrow_hashref()) { if ($currenttype ne $row->{type}) { if ($count > 0) { print “ } printf(“ {type})); $currenttype = $row->{type}; } $count++; printf(“ $row->{title}, $row->{adda}, $row->{addb}, ); Chapter 16 — Generating Google Earth Feeds 323 printf(“”,lc($row->{type})); printf(“ $row->{lng}, $row->{lat}, ); } $sth->finish(); print(“ The preceding script also introduces another concept. You extrude the point from the ground. This creates a line between the icon used to represent the entity and its actual location on the ground.To do this, when defining the You then need to set the altitude of the point, first by defining the relationship between the actual point on the ground and the elevation at which you want to create the The relativeToGround specification sets the system so that the height is relative to the height of the ground where the marker is created. So, if you specify the altitude of the point as 250m, but the elevation of the location is already 68m, then the marker would display at 318m above sea level. Other options are clampedToGround (the altitude is ignored, this is the default mode) and absolute, where the altitude is exactly as specified (250m would display at 250m above sea level, even if the elevation of that point was more than that amount). Figure 16-8 shows the resulting information in Google Earth. You can see how the markers appear to float above the map, but a line is clearly connected from the marker to the real latitude/ longitude of the point. Because the information is floating, rotating the map shows the icons constantly associated with the right location (see Figure 16-9). Although the view is quite confusing here, users have the ability to include and exclude the different businesses they want to view because businesses are grouped into appropriate folders. The organization (providing the KML is generated appropriately) is automatic and is a lot easier to use than the system that had to be developed within Google Maps. 324 Part IV — Google Earth Hacks FIGURE 16-8: Using custom icons and extruding information. FIGURE 16-9: Viewing icons with a tilted and rotated map. Chapter 16 — Generating Google Earth Feeds 325 Wrapping Up Google Earth handles a lot of the application logic that requires JavaScript and programming in Google Maps.To create similar effects within Google Earth you need only generate the appropriate KML. This chapter covered the basics of generating markers and points within KML. The basic point is easy to create. In most cases it requires only the latitude and longitude of the point. Markers can then be further customized by adding icons and you can even help to improve the visibility by extruding the icon above the map, making the marker more visible, particularly when the map is rotated or tilted. You also saw how to refresh KML data. The refresh system allows KML to be automatically reloaded, and that provides an element of interactivity that enables sequences or time-based interaction to be overlaid on top of the Google Earth satellite data. History and Planning with Google Earth Location Photos Iwas fortunate enough to go Pompeii during the writing of this book. Pompeii is a fascinating place, because almost the entire town (or at least that which has been uncovered) is intact—an amazing feat considering it is almost 2,000 years old and was buried under many feet of volcanic ash from the eruption of Mount Vesuvius in 87 A.D. As a Roman town it offers a unique insight into Roman life. While there I took hundreds of photos, but though I can show and describe the contents of the photos, it is difficult to give a context in terms of the layout of the town to someone who has never been there. Using Google Earth, the photos taken at Pompeii can be shown in the context of a satellite shot of the Pompeii site. The view can include the heading and even the photo itself to help the viewer make sense of both the satellite image and the photo. Using a Photo for a Placemark In Chapter 16, icons were used to highlight particular areas on the map that related to specific businesses. Using a photo as an alternative mark is one way of highlighting the places you visited while on vacation. It can also be used with any photo to give the photos some context. For example, Realtors could use photos of a property and a satellite image (or the view from the windows of different rooms) to show what the real estate looks like from different directions. When using this method, be aware that the photos may overlap each other. Some careful placing—using altitude and extrusion—to highlight the points can help to make the individual items visible. Figure 17-1 shows an example using icons in this way, and Figure 17-2 shows the same information but with a slightly different camera angle, to show how the overlapping of the icons can obscure, rather than help, the display of information. To achieve this display, a number of different techniques were used. ˛ Create placemarks from photos ˛ Create KMZ files ˛ Generate 3D models chapter in this chapter 328 Part IV — Google Earth Hacks FIGURE 17-1: Using photos for icons. FIGURE 17-2: An alternative photo-based icon view. Chapter 17 — History and Planning with Google Earth 329 Scaling the Icon By default, Google Earth creates a relatively small icon based on the image that is provided, regardless of the size of the image. This is to prevent the image from dominating the map, when it is only really referring to a placemark. To alter this behavior, styles must be defined that specify the format of the icon and the label used to highlight the placemark. The key element in the following code is the Icon reference, which refers to the image that will be used for an icon, and the scale entity, which scales the size of the icon in the placemark: Figure 17-3 shows the difference between a non-scaled and a scaled icon. FIGURE 17-3: A non-scaled (small) and scaled (large) icon. 330 Part IV — Google Earth Hacks Setting a View When dealing with photographs, the direction in which the camera was pointing when the photograph was taken is a significant part of what makes the photo special. For example, a photo of the Bay of Naples, where Pompeii is located, can show a number of different elements. If the photo was taken from Naples facing the southeast, you’d be taking a photo of some mountains.To a visitor to the area, they are quite obviously the mountains to the east of Sorrento, but they could easily be confused for a picture of Vesuvius. By adding a heading and direction to a placemark, the direction of the camera lens is obvious. To achieve this, a LookAt element must be included with each tag.When the user doubleclicks a tag, the information in the LookAt tag is used to determine the camera (or eye) view point within Google Earth. There are six elements to the LookAt fragment: Longitude: The longitude of the point. Latitude: The latitude of the point. Altitude of the point: (Optional.) The altitude of the point. Range: The altitude of the camera or eye. Tilt: The angle of the camera. Heading: The compass heading of the camera. Thus a view point equal to a bird’s-eye view of the main square in Pompeii can be created using the following code: The LookAt element is placed immediately within the Placemark element: ... When the placemark is double-clicked, the camera moves to this location.When it is single clicked, nothing happens. Chapter 17 — History and Planning with Google Earth 331 Adding Detail to a Placemark The info window in Google Maps is an effective way of providing more detailed information for a placemark. Google Earth automatically creates these windows based on information within the placemark can be described using this: The content in this section can be plain text, as shown here, but it can also be HTML.To embed HTML it must be escaped. There is a longer solution for this that requires escaping the HTML (particularly the angle brackets), like this: temple. <img src=”images/DSC01155.JPG”> A simpler method is to use the XML data embedding format. For example, you could include the photo in the placemark window using the following:  ]]>Using this method, the points on the map could be returned to standard placemarks and the placemark window used to display the photo. Final KML Putting everything in the previous sections together, you can build a single KML file that describes a number of points, and the photos taken at those points, for the trip to Pompeii. Only three points are detailed here, but an unlimited number could theoretically be introduced:  ]]>332 Part IV — Google Earth Hacks streets leading off the square.  ]]>]]>Figure 17-4 shows the main map, with Figures 17-5 and 17-6 showing two of the photos from the available points. Note that in each case the placemark has been double-clicked to move the map to the new viewpoint. Chapter 17 — History and Planning with Google Earth 333 FIGURE 17-4: Basic placemark in Pompeii. FIGURE 17-5: A council building in Pompeii. 334 Part IV — Google Earth Hacks FIGURE 17-6: Looking backwards toward the main square. Generating the Information in Google Earth Although it is tempting to produce all of the information completely manually (which is certainly possible for typical addresses and locations that can be determined using techniques shown earlier in this book), an easier alternative is to use the Google Earth application.To create a new point, choose File➔Add➔New Placemark. All of the options, including the camera view, description, elevation, and extrusion information can be set entirely within the panel. Click the Advanced checkbox to set the additional options. You can see the various settings across three different panels: Style (Figure 17-7), Location (Figure 17-8), and View (Figure 17-9). Once you have created the various placemarks that you want, you can save the placemarks into a separate file and even generate a suitable folder structure. If you have included graphics for icons into your placemarks, Google Earth will create a KMZ file rather than a KML file that incorporates the KML and images into a single Zip file. The same method can be used with your own creations. Chapter 17 — History and Planning with Google Earth 335 FIGURE 17-7: Setting a placemark Style. FIGURE 17-8: Setting a placemark Location, altitude, and extrusion. 336 Part IV — Google Earth Hacks FIGURE 17-9: Setting the View for a placemark. Generating a KMZ File Generating a plain KML file is fine when either the information or the icons and other data are available freely on the Internet. However, there are times when you want to create a standalone file that incorporates the KML with the icons, images, and any other files that make your Google Earth file. The format is quite straightforward. It is simply a Zip file that contains the KML and images. For clarity, you should use the following format: doc.kml: The main KML file. images/: A directory for icons and photos to be included in the file. Within the KML, you can refer to files directly according to this structure. For example, a photo could be included in the description for a placemark using this: You can use any appropriate Zip-compatible software. From a Unix or Linux machine (including Mac OS X) with a command-line client, you could use the following, for example: $ zip -r Pompeii.kmz doc.kml images/ Chapter 17 — History and Planning with Google Earth 337 Within Windows you can use WinZip to create a suitable file, but you need to rename the file to have the .kmz extension. Revisiting the Realtor’s Toolkit In Chapter 12 examples of both archaeological- and realty-related tools in Google Maps were examined. Both followed similar principles, the overlay of information that is known about a location, either in the past or the potential in the future. Within Google Earth the same principles can be used to display information, either in an identical manner or in a far more interesting alternative. Using an Overlay A simple overlay was used in Chapter 12 to suggest a potential office plan and layout. The display was simplistic, partially because of limitations in Google Maps, but also because with just a flat image to play with, there is very little that could be done to alter the view and representation of the office plan.With Google Earth you can follow the same principles to add an image overlay to the map. Figure 17-10 shows the overlay in an almost identical situation to the one used in Chapter 12. FIGURE 17-10: Display of a simple overlay. 338 Part IV — Google Earth Hacks Because this is Google Earth, the overlay is of course attached to the map. If the view is rotated or tilted, the overlay rotates and tilts with the map accordingly, as demonstrated in Figure 17-11. FIGURE 17-11: Rotated map and overlay. The KML generated in the preceding process shows how the image is overlaid. Unlike Google Maps, where the TPhoto extension was used, Google Earth supports the operation directly within the application using KML to define the structure: Chapter 17 — History and Planning with Google Earth 339 The key element is how the location of the overlay is associated with the map. The north, south, east, and west elements set the borders of the image as it will be associated on the map. The other elements are as follows: Icon: Defines the overlay image. viewBoundScale: Specifies how much of the display real estate should be used to show the overlay. Color: Specifies the color and opacity of the overlay. The color is specified as four twocharacter hexadecimal values, between 0 and 255. The first value is the alpha (opacity) channel. The value specified in this case is 77 (hex), or 119 decimal, or about 47 percent. Although the information displayed is useful, with a 3D environment it would be much better to give a proper 3D representation of the offices. Creating a 3D Structure To create a 3D structure, for example, the representation of an office, you combine latitude/ longitude references with extrusion and altitude to generate a “solid” 3D object on the map. The key is the Polygon element, a base structure that defines a simple multi-point shape made up of the lines that connect latitude/longitude points.Without extrusion, a Polygon would draw a simple shape.With extrusion and altitude you solidify the polygon. The basic structure for a polygon is as follows: -97.59277582168579, 35.282008632343754,100 -97.59277582168579, 35.278137436300966,100 -97.59017944335938, 35.278137436300966,100 -97.59017944335938, 35.282008632343754,100 -97.59277582168579, 35.282008632343754,100 340 Part IV — Google Earth Hacks The outerBoundary element defines the outer line of the polygon. Everything inside is considered part of the solid shape. The coordinates are specified, one per line, but really you need only separate each coordinate by a space. Remember, just as with bounding boxes in Google Maps, you must specify at least one more point for each side of the shape because you are drawing lines from point to point to point. In this case, four sides require five points, each of the four corners and the first corner again to complete the polygon. You can also generate shapes based on multiple polygons by using the MultiGeometry option, including each Polygon definition within the MultiGeometry element. Using these techniques, the simple flat image overlay demonstrated earlier could be redeveloped into a 3D model of the office building using the following KML: provide a view for clients. 50 -97.58590936660767, 35.28360260045482, 50 -97.58260488510132, ; 35.28360260045482, 50 -97.58260488510132, 35.27654336061367, 50 -97.58590936660767, ; 35.27654336061367, 50 Chapter 17 — History and Planning with Google Earth 341 100 -97.58590936660767, 35.28360260045482, 100 -97.58260488510132, 35.28360260045482, ; 100 -97.58260488510132, 35.279, 100 -97.58590936660767, 35.279, 100 250 -97.58590936660767, 35.28360260045482, 250 -97.58260488510132, 35.28360260045482, ; 250 -97.58590936660767, 35.28, 250 35.282008632343754,150 -97.58904218673706, 35.278137436300966,150 -97.58638143539429, ; 35.278137436300966,150 -97.58638143539429, 35.282008632343754,150 -97.58904218673706, ; 35.282008632343754,150 342 Part IV — Google Earth Hacks 35.282008632343754,100 -97.59277582168579, 35.278137436300966,100 -97.59017944335938, ; 35.278137436300966,100 -97.59017944335938, 35.282008632343754,100 -97.59277582168579, ; 35.282008632343754,100 The resulting 3D office plan can be seen in Figure 17-12, and, because it is a proper 3D structure, Figure 17-13 shows an alternative view. FIGURE 17-12: A 3D office demonstration. Chapter 17 — History and Planning with Google Earth 343 FIGURE 17-13: An alternative view. Unfortunately, I am no 3D artist, but you can find numerous other examples of 3D structures defined within the Google Earth application when you add the Buildings overlay to your map. Wrapping Up The facilities in Google Earth can turn the basic principles learned in Google Maps into a much richer environment for showing information. Because the map can be rotated and manipulated, unlike the flat model used by Google Maps, you can develop much more interesting views of data and information, such as holiday photos. Because direction and orientation are implied in the display, the photos are given much more context than simple pushpoints on the map. Using built-in 3D modeling, you can represent offices, buildings, and other elements in a way that provides a much easier-to-understand representation of a structure.With some manipulation of the camera, you could even give a representation of what a buyer could expect to see through the windows of stores in the buildings. ˛ Useful resources for Google.com ˛ Additional sources of information ˛ Geocoder links ˛ Google Maps tools ˛ Other mapping services appendix in this appendix Resources Google Maps has generated a significant following, and this has, in turn, led to a stunning array of web sites that provide information, examples, tutorials, and help for working with and developing Google Maps applications. I’ve distilled the basics of these links into this appendix. Please note that the information in this appendix was correct at the time it was written. For a more complete and up-to-date resource page, please visit the MCslp Map Works web site (http://maps.mcslp.com). Google Resources As a web company, Google has done a lot to provide access to as much information as possible on as many different sites as possible. The primary considerations for this appendix, of course, are the main map sites that Google uses to provide the information. You can view any part of the world through the Google Maps interface. Google also has specially allocated URLs that take you to specific countries so that you don’t have to go to the generic U.S. site and search or scroll until you find the area you want. Of course, you can go wherever you like when developing your own Google Maps. Table A-1 provides a list of the main sites, including Google Moon. Table A-1: Google Map Services Map URL Google Maps USA http://maps.google.com Google Maps UK http://maps.google.co.uk Google Maps Japan http://maps.google.co.jp Google Maps China http://bendi.google.com Google Moon http://moon.google.com Google Earth http://earth.google.com 346 Part IV — Google Earth Hacks The Google Moon site is unique in that it shows only the area (and the associated markers) used for the moon landings. The site was released on July 20, 2005, to mark the 36th anniversary of the Apollo 11 moon landing. Google Maps API www.google.com/apis/maps/ You can find more information, read the documentation, and view help pages on the main Google Maps API site. Google Maps API Documentation www.google.com/apis/maps/documentation/ This is the main documentation page for the entire Google Maps service. The information provided on this page is the current version of the Google Maps API documentation. You should visit the site regularly to ensure that there have not been any important changes to the documentation and API. Google Maps API Help www.google.com/apis/maps/faq.html Here you can find the FAQ for working and using the Google Maps API. Google Web API www.google.com/apis/ The Google Web APIs provide an interface to the Google system for searching the Google databases for information. Google Maps Groups There are two groups for Google Maps: The Google Maps group (http://groups-beta.google.com/group/Google- Maps) provides basic information and discussion on the Google Maps service. The Google Maps API group (http://groups-beta.google.com/group/ Google-Maps-API) provides discussion of the Google Maps API and information on how to construct web sites based on the Google Maps system. Appendix A — Resources 347 Information Sources To get the most out of the Google Maps service, you will almost certainly need to make use of additional Google Maps resources and web sites. This section lists some of the key components, including sites that themselves provide more information on and links to the Google Maps service. Google Maps Mania http://googlemapsmania.blogspot.com/ This blog documents Google Maps services, changes to the documentation and service offerings, and general information on the web-mapping world. Overall, it provides one of the best ranges of resources, as well as links both to vital resources and to example Google Maps services. Maplandia.com The Maplandia site provides links to Google Maps pages that take you straight to a specific country, town, city, or other location through a series of geographical locations. Once you’ve found the location you want, you can further search for locations within the specific area. Google Maps on Wikipedia http://en.wikipedia.org/wiki/Google_maps The Google Maps entry on Wikipedia provides a range of additional links and information on the Google Maps service and associated web sites. Google Sightseeing www.googlesightseeing.com/ This site shows images taken from Google Maps and Google Earth that show interesting structures or images. Geocoders Google does not provide a geocoding mechanism (that is, a way of mapping a given address or worldwide location into the latitude and longitude required to redirect Google Maps to a specific location). This section lists a number of solutions to this problem. You can use some of them directly within a Google Maps browser application; others can be used from within a server-side application to build a list of points for your main application. 348 Part IV — Google Earth Hacks MGeocoder http://brainoff.com/gmaps/mgeocoder.html MGeocoder provides a JavaScript overlay that enables you to search directly for a given location. Geocode America www.geocodeamerica.com/ This is a web service–based interface to a Geocode database for America. You can supply any U.S. address and obtain the Geocode information you require. Geocoder http://geocoder.us/ This is another web service–based interface for finding Geocodes from addresses. Primarily a U.S. service, Geocoder also provides a Canadian and Argentinean service. Google Maps Tools A number of tools have been produced to make it easier to produce Google Maps and to provide examples and extensions to the Google Maps functionality. gMap it! The gMap extension for Firefox allows you to find and search for information based on publicly listed phone numbers, which can then be used to display the location and directions within Google Maps. Mobile GMaps www.mgmaps.com/ Being able to use Google Maps on a mobile device is obviously a good combination, and Mobile GMaps enables you to use Google Maps on mobile devices (phones, PDAs) that support the J2ME ( Java Mobile Environment) standard. MapBuilder www.mapbuilder.net/ MapBuilder provides a complete web environment for building Google Maps. You can specify locations, add HTML (to be displayed in map points and pop-ups), and choose your point Appendix A — Resources 349 icon. The result is a web page that you can download and use in your own applications once you use your own Google Maps API key. MapKi http://mapki.com A Wiki that provides information and resources on using mapping APIs, including Google Maps. Competitors and Alternatives Although Google Maps and Google Earth are not the first search services available on the Internet, they were the first to make a publicly available API to enable programmers and other individuals to embed Google Map–based applications into their own web pages instead of redirecting users to another site. MapQuest http://mapquest.com/ The MapQuest site provides street maps only of the U.S.; Canada; and much of western, southern, and northern Europe. MapQuest is part of AOL. Virtual Earth Virtual Earth is part of the Microsoft Network (MSN) web site; it overlays satellite imagery and aerial photography of the earth over a 3D map. As well as providing map-search functions, Virtual Earth can also show maps according to specific addresses, towns, or cities, or via a business name or type search. Yahoo! Maps http://maps.yahoo.com/ Yahoo! Maps provides mapping information for the U.S. and Canada. A9 Maps Amazon’s search engine, A9, has a mapping service that provides U.S. street maps and driving directions. In an interesting twist to the basic street-mapping service, A9 Maps also provides street-level photography that allows you to see what a street looks like in addition to viewing its location on the map. 350 Part IV — Google Earth Hacks Multimap.com www.multimap.com/ Multimap.com is a U.K.-based provider of mapping information. It is a full road-mapping service (for the U.K., continental Europe, and the U.S.) combined with aerial photographs and local information. Multimap was one of the early Internet-based mapping companies, and U.K. companies often use the site to direct people to businesses. Map24 http://map24.com Map24 is an Internet mapping application that uses a Java-based interactive interface for building the maps and providing the interactive elements of the Map interface. The site currently supports the U.S., Europe, Brazil, and the Middle East. Additional Support In addition to this user guide, Google offers a number of resources that can help you use and enjoy Google Earth. These include: l FAQs: View a list answers to frequently asked questions (FAQs) about Google Earth. l Google Earth Help Center: Use the Help Center at any time to find additional information. l Troubleshooting: View information that specifically pertains to troubleshooting issues with Google Earth. l Google Earth Community: Learn from other Google Earth users by asking questions and sharing answers on the Google Earth Community forums. Navigating in Google Earth In Google Earth, you see the Earth and its terrain in the 3D viewer. You can navigate through this 3D view of the globe in several ways: l Using a mouse l Using the navigation controls You can also manipulate your view of the earth by tilting the terrain for perspectives other than a topdown view. Finally, you can reset the default view for a north-up, top-down view wherever you are. Using a Mouse To get started navigating with your mouse, simply position the cursor in the middle of the 3D viewer (image of the earth), click one of the buttons (right or left), move the mouse and note what happens in the viewer. Depending upon which mouse button you press, the cursor changes shape to indicate a change in behavior. By moving the mouse while pressing one of the buttons, you can: l Drag the view in any direction l Zoom in or out l Tilt the view (requires middle button or scroll wheel) l Rotate the view (requires middle button or scroll wheel) The following list describes all the actions you can accomplish using the mouse. l Move the view in any direction (north, south, east, or west) - To move the view, position the mouse cursor on the viewer and press the LEFT/main mouse button. Notice that the cursor icon changes from an open hand to a closed hand . Pull the viewer as if the hand cursor is like a hand on an actual globe, and you want to drag a new part of the earth into view. You can drag in any direction to reveal new parts of the globe, and you can even drag in circular motions. l Drift continuously across the earth - If you want to drift continuously in any direction, hold the left/main mouse button down. Then, briefly move the mouse and release the button, as if you are "throwing" the scene. Click once in the 3D viewer to stop motion. l Zoom in - There are a number of ways to zoom in with the mouse. m You can double-click anywhere in the 3D viewer to zoom in to that point. Single-click to stop, or double-click to zoom in more. m If your mouse has a scroll wheel, use it to zoom in by scrolling towards you. Use the ALT (alt/option on the Mac) key in combination with the scroll wheel to zoom in by smaller increments. m You can also position the cursor on the screen and press the RIGHT mouse button (CTRL click on the Mac). Once the cursor changes to a double arrow, move the mouse backward or pull toward you, releasing the button when you reach the desired elevation. If you want to zoom continuously in, hold the button down and briefly pull the mouse down and release the button, as if you are "throwing" the scene. Click once in the viewer to stop the motion. m On some Macintosh laptops, you can drag two fingers across the trackpad to zoom in and out. l Zoom out - There are a number of ways to zoom out with the mouse. m Using the RIGHT mouse button (CTRL click on the Mac), double-click anywhere in the 3D viewer to zoom out from that point. The viewer will zoom out by a certain amount. Single-click to stop, or right double-click (CTRL click on the Mac) to zoom out more. m If your mouse has a scroll wheel, you can use the scroll wheel to zoom out by scrolling away from you (forward motion). Use the ALT (alt/option on the Mac) key in combination with the scroll wheel to zoom out by smaller increments. m You can also position the mouse cursor on the screen and press the RIGHT mouse button (CTRL click on the Mac). Once the cursor changes to a double arrow, move the mouse forward or push away from you, releasing the button when you reach the desired elevation. If you want to zoom continuously out, hold the right button (CTRL click on the Mac) down and briefly push the mouse forward and release the button, as if you are "throwing" the scene. Click once in the viewer to stop motion. l Tilt the view - If your mouse has a either middle button or a depressible scroll wheel, you can tilt the view by depressing the button and moving the mouse forward or backward. If your mouse has a scroll wheel, you can tilt the view by pressing the SHIFT key and scrolling DOWN to tilt the earth to "top down" view, or scrolling UP to tilt the earth for horizon view. See Tilting and Viewing Hilly Terrain for more information. l Rotate the view - If your mouse has either a middle button or a depressible scroll wheel, you rotate the view to the left by clicking on the middle button and moving the mouse to the left. To rotate the view right, click on the middle button and move the mouse to the right. You can also use the CTRL ( on the Mac) key in combination with the scroll wheel to rotate the view. Press CTRL ( on the Mac) and scroll UP to rotate clockwise, CTRL ( on the Mac) + scroll DOWN to rotate counter-clockwise. See Tilting and Viewing Hilly Terrain for more information. l Mouse Wheel - See above. To change these settings, click Tools > Options > Navigation > Navigation Mode > Mouse Wheel Settings (on the Mac: Google Earth > Preferences > Navigation > Navigation Mode > Mouse Wheel Settings). Move the slider to set how fast or slow your viewpoint of the earth zooms in or out. Check Invert Mouse Wheel Zoom Direction to reverse the direction of zooming when you use the mouse wheel. l Pan and Zoom navigation - This mode is on by default when you start Google Earth. You can return to this mode from other modes by doing one of the following: m Type Ctrl ( on the Mac) +T. When this mode is activated, the cursor changes to a hand symbol. m (Windows and Linux) Tools > Options > Navigation > Navigation Mode > Pan and Zoom . (Mac) Google Earth > Preferences > Navigation > Navigation Mode > Pan and Zoom If you use a joystick or other non-mouse controller, you can also change how perspective moves in the 3D viewer under Controller settings. Choose User-Based to move your particular vantage point or Earth Based to move the globe. Check Reverse Controls to reverse the actions of the joystick. l GForce navigation (advanced) - To change to this navigation mode, do one of the following: m Type Ctrl ( on the Mac) + G to change when window focus is in the 3D viewer m (Windows and Linux) Tools > Options > Navigation > Navigation Mode > Flight Control. (Mac) Google Earth > Preferences > Navigation > Navigation Mode > Flight Control This mode is in effect when the navigation cursor changes to an airplane. In addition, the effects of G-Force mode are most noticeable the closer you are to the terrain, and become less exaggerated the higher your eye elevation. The behavior of this navigation mode simulates that of a joystick, where the direction your mouse moves indicates specific joystick moves. If you are familiar with using a joystick, you'll be able to use this mode easily. To pan left or right, or to tilt the horizon left or right, left-click and move the mouse right/left of center. To tilt to top-down view, left-click and move the mouse forward (away from you). To tilt to horizon view, left click and move the mouse back (toward you). To accelerate, right-click (CTRL click on the Mac) and move the mouse forward. To decelerate, right-click (CTRL click on the Mac) and move the mouse backward. The response in the 3D viewer to your mouse movements is related to the vigorousness of your mouse movements, so you can test this mode out slowly using movements. To return to standard trackball navigation mode, type Ctrl ( on the Mac) + T. To stop motion in the viewer at any time, press the spacebar. l Click-and-Zoom navigation - To change to this navigation mode, choose: m (Windows and Linux) Tools > Options > Navigation > Navigation Mode > Click-and- Zoom m (Mac) Google Earth > Preferences > Navigation > Navigation Mode > Click-and-Zoom When the 3D viewer enters this navigation mode, the cursor changes to a cross-hair mark. Here, navigation with the mouse is limited: left-click to zoom in a set distance, and right-click (CTRL click on the Mac) to zoom out a set distance. Use the navigation controls to pan and rotate. Return to the standard trackball mode by typing Ctrl ( on the Mac) +T. Using the Navigation Controls Note - To view and use the navigation controls, move the cursor over right corner of the 3D viewer. The navigation controls automatically appear whenever you do this; they fade from sight when you move the cursor elsewhere. See also Showing or Hiding Items in the 3D Viewer. The Google Earth navigation controls offer the same type of navigation action that you can achieve with mouse navigation. In addition, you can use the controls to tilt the view (perhaps for a perspective on terrain) or to rotate the viewer around the center. The following diagram shows the controls and explains their functions. 1. Use the tilt slider to tilt the terrain toward a horizon view. Move the slider to the left for a topdown view or to the right for a horizon view. Click the icons at the end of the slider to reset the tilt all the way to a top-down view or to a horizon view. 2. Use the joystick to move the center point of the view down, up, right or left. Click the center, hold the mouse button, and move in any direction. 3. Click the direction arrows to move the view in the direction you wish. 4. Click the north up button to reset the view so that north is at the top of the screen. 5. Use the zoom slider to zoom in or out (+ to zoom in, - to zoom out). Click the icons at the end of the slider to reset the zoom all the in or out. 6. Click and drag the navigation ring to rotate the view. Note: You can also use the keyboard to control navigation, see 3D Viewer Navigation in Keyboard Controls for more information. Tilting and Viewing Hilly Terrain When you first start Google Earth, the default view of the earth is a "top-down" view, which looks like the view straight down out of an airplane window when you are sufficiently zoomed in. l Tilt the terrain from 0 - 90 degrees - You can use the mouse or the navigation controls to tilt the view in order to see a different perspective of the area you're exploring. You can tilt to a maximum of 90 degrees, which provides a view of the object as well as the horizon, in some cases. l Turn on terrain - Using the tilt feature is particularly interesting when you are looking at a part of the earth where the terrain is hilly, so be sure to also have the terrain check box selected in the Layers panel when tilting the view. l Rotate the view for a new perspective - Once you have tilted the view so that you are looking at a particular object, such as a hill, you can also rotate around that object. When you do this, the object remains in the center of the view, but you look at it from different perspectives (i.e., north, south, east, west) as you rotate around it. l Use the middle mouse button (if available) for seamless movement - If your mouse has a middle button or a depressible scroll wheel, you can depress the button to both tilt and rotate the view. Movements up or down tilt the view, and movements left or right rotate the view. See Using a Mouse for more information. The following figures show a comparison view of Mount Shasta in California with and without tilt enabled. Top down view Tilted view You can adjust the appearance of the terrain if you would like the elevation to appear more pronounced. To do this, click Tools > Options > 3D View from the Tools menu (for the Mac, choose Google Earth > Preferences > 3D View) and change the Elevation Exaggeration figure. You can set it to any value from 1 to 3, including decimal points. A common setting is 1.5, which achieves an obvious yet natural elevation appearance. See Viewing Preferences for more information. Resetting the Default View After tilting and rotating the 3D view in Google Earth, you can always quickly reset to the default north-up and top-down view by clicking on the appropriate buttons in the navigation controls. l Click the North-up button to reset the view so that north is at the top of the viewer. l Click the Reset Tilt button to reset tilt to the default "top-down" view. l (Windows and Linux only) Click in the 3D |
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پست الکترونیک آرشیو وبلاگ لطفا برای حمایت از ما بر روی لینک زیر کلیک کنید
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