If you're taking overhead pics in Google Earth and stitching them manually you can make yourself a transparent overlay grid image. This you can use to plot out a raster of your area, toggle it off when you're taking the pictures. Also, don't change the zoom level, this will make it very difficult to stitch the raster as the images would be out of proportion to each other. Turn off 3d terrain too.
Well what you want is the GE pixel dimension to match whatever you are using in V3. Usual sat maps are 1 pixel = 1 meter. What height you use in GE is monitor resolution dependent. By taking a screenshot of GE and using the distance scale (in the lower left corner), you can determine the number of pixels per meter real world dimensions at the height of your screenshot.
I then use FRAPS to snap images of the entire image, which I cut and paste together. Make sure you turn off the side bar, nav tools etc to maximize your image, and have Terrain turned off to avoid distortion. Very important to ensure you don't change the GE height above ground by mistake, and use the 'R' key to ensure alignment. Once I have the entire area pieced together I can re-size it using the ratio I determined when I took a screenshot with the scale visible.
Obviously you want to get the best image, but zooming in all the way in GE is not always the answer because their image's resolution. Plus the more you zoom in the more images you have to take and piece together. Of course if you zoom out too far you lose a lot of detail, too. So you have to balance.
Other method is to use automated Google earth map downloader tools available on the net.
High parameter is only the view high of the camera not the distance.
Use the “*Lineal Tool” to measure the size then you can zoom to the required high.
If you want 1 pixel 1m sat map for your 40960 map you would need to capture 100 of this pics (depending on landmass). If you got a atom fueled supercomputer then do it.