GPS for Dummies.pdf - Engineering Surveyor

Chapter 14: From the Air with USAPhotoMaps229TerraServer-USA limitationsThe first time you see USAPhotoMaps displayTerraServer-USA aerial photos, you’re probablygoing to say, “Wow! This is like having my ownpersonal spy satellite.” Well, sort of, but thereare a few catches: Yanks only: TerraServer-USA provides aerialphotos and maps of United States locationsonly. And although the aerial photo databaseis fairly complete, some areas in the U.S.don’t have photo data. Not always current: TerraServer-USA aerialphotographs tend to be not very current. Infact, they can be up to ten years old becausethe USGS produces new sets of aerial photosonly as often as needs and budgets allow. No color: Only black-and-white photos arecurrently available. TerraServer-USA doesplan to carry more recent, high-resolution,color aerial photographs that the USGS hasproduced for selected urban areas, but it willbe many years until color aerial photographsare available of most of the United States. Data transfer hiccups: Network outages andserver upgrades can disrupt TerraServer-USA data transfers.Read more about UTM, latitude, and longitude in Chapter 2. If you don’t knowthe latitude and longitude coordinates of the location you’re interested inseeing, quickly skip over to Chapter 11 to read how to find coordinates ofplace names.As an example, create an aerial photomap of Seattle, Washington.1. Enter the name, latitude, and longitude in the New Map dialog box.(See Figure 14-1.)2. Click OK.• Name: Seattle• Latitude: 47.61431• Longitude: 122.32898A series of gray squares appear onscreen.3. Download aerial photos from TerraServer-USA for the area that youspecified (with the latitude and longitude coordinates). Make sure thatyou’re connected to the Internet and then press the F key.A mosaic of aerial photograph images replaces the gray squares as thescreen is filled with data from TerraServer-USA. The final result is shownin Figure 14-2.If you’re using a firewall, your computer might complain when USAPhotoMapstries to connect to TerraServer-USA. Because the program is just downloadingmap data, you can give permission for USAPhotoMaps to access the Internet.