Mapping Hacks

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Chapter 6, Mapping on Your Desktop

#64 Mapping Local Areas of Interest with Quantum GIS

HACK

clicking on the hyperlink shown in Figure 6-2, we can get to the page that

has links to both the USGS Digital Orthophoto Quadrangle (DOQ) aerial

photograph and the Digital Raster Graphic (DRG), which is the digitized

USGS topographic map. Microsoft’s Terraserver

[Hack #4] hosts both of these

items.

Getting the Data

Using the DRG and DOQ links on the GNIS search result page, we can navi-

gate Terraserver and download the images.

To fetch the DRG:

1. Click on the View USGS Digital Raster Graphic (DRG) link on the GNIS

results page. The Terraserver web site loads the selected area of interest.

2. In the left panel, change the map size to Large.

3. At the top of the page, click on Download.

4. Follow the instructions to the left of the image to save it. When saving

the image, give it a reasonable name (e.g., burro_canyon_topo.jpg).

5. To display the image in the proper coordinate system, we also need the

world file. Click on the “GIS World Coordinates” link in the left panel

and save the coordinate file as burro_canyon_topo.jgw. This file is

known as a world file and is used to place the image in a real-world

coordinate system.

Figure 6-1. Searching the GNIS