GPS for Dummies.pdf - Engineering Surveyor

318Part IV: Using Web-hosted Mapping Serviceson the Web costs for bandwidth and storage; what’s free today —particularly from commercial sites — might not be around tomorrow.TerraServer-USAIn 1998, Microsoft, Compaq, the USGS, and several other partners launched theTerraServer Web site. The site was a technology demonstration for Microsoftsoftware and Digital (which had recently been purchased by Compaq) hardwareand was dubbed “the world’s largest online database.” TerraServer had acollection of compressed aerial photos and satellite images that took up over aterabyte (TB) of space. (A terabyte, which is 1,024GB, was a lot of disk spaceback then.) Anyone with an Internet connection could freely browse throughthe database of images.Now renamed TerraServer-USA (www.terraserver-usa.com), this site providesaerial photos and topographic maps supplied by the USGS for justabout anywhere in the United States. Although most of the aerial photos thatTerraServer-USA provides are black-and-white, TerraServer-USA is addingUSGS Urban Areas aerial photography collections of mapping major metropolitanareas with high-resolution, color aerial photos.Displaying TerraServer-USA aerial photosTo display an aerial photo from TerraServer-USA, you first enter some searchcriteria. You can search for aerial photos three different ways.Zoom-in searchesWhen you visit the main page of the TerraServer-USA site at www.terraserver-usa.com, you’re greeted with a map of the world. Areas displayedin green contain map data. Move the cursor to a location that youwant to view and click. Keep clicking and zooming in until the aerial photoyou’re interested is displayed.General searchesSearch for a TerraServer-USA aerial photo of a city or well-known locationfrom the Search TerraServer text box. When you click the Go button, a list ofthe aerial photos that match the text is displayed. Click the text thatdescribes the image you’re interested in to display it.You can make your search more specific by entering a city name followed by acomma, a space, and the standard two-letter postal abbreviation of the state.For practice, try searching for a well-known landmark, such as the SpaceNeedle in Seattle, Washington. If you enter Space Needle, you get the aerialphoto of downtown Seattle as shown in Figure 20-1. There’s not much detail,but you can find out how to increase the resolution in the section titled“Changing image resolution in TerraServer-USA.”