This is a little example of how you can use an aerial photo as a basemap. One place to get aerial photos is from
Acme Mapper (pops in new window), a front-end for
TerraServer. You can input geographic coordinates, as well as other parameters such as map size, resolution, etc. A map is created with your input coords near the center. The map display is tiled, so to use it with pointMapper, click the Save Map button below the map and a consolidated image is created. You can just right click on this consolidated image and save it to your map area.
Below the map you will see something like this:
World File parameters:
2
0
0
-2
435200
5115600
10T (UTM)
WGS-84
The two large numbers, in this case 435200 and 5115600, are the coordinates of the upper left corner of the image in UTM zone 10T (or 10N) coordinates. This is a 2 meter per pixel resolution image, so to get the lower right coordinates, multiply the image width (600px) by 2 and the image height (625px) by -2 and add to the result to 435200 and 5115600, respectively. This is all you need to create a georeferenced map for pointMapper. Look at the
XML (pops in new window) we created for the aerial photo we downloaded.
You may not need to have a georeferenced map. Sometimes it's easier to just look at the photo and find locations of interest. You can get the canvas coordinates you need by using the pointMapper Locate tool. If this is the case the
XML (pops in new window) does not require the
coverage information nor the UTM information.