In case anyone finds it useful, here is how you can display topographic lines on top of an aerial.

The following link starts Gmap4 (I am the developer) and if you zoom in until the scale in the lower left says 500 ft then you will see topo lines on the Google aerial for anywhere in the U.S.

http://www.mappingsupport.com/p/gmap...ansparent=true

To start zooming in to your area of interest, try Menu ==> Search to get close and then zoom/pan. To manually zoom, use your mouse wheel or the sliding control near the upper left corner of the map.

To turn the topo lines on/off, click the button in the upper right corner of the map then scroll down to the Overlay section and click "topography_lines".

The topo line data comes from a GIS (Geographical Information Service) server run by the feds. That GIS data displays the topo lines on top of any basemap.

The Gmap4 homepage has a FAQ, examples, quick start info (in the Help file) and more to quickly get you up to speed.

Gmap4 default map: http://www.mappingsupport.com/p/gmap4.php (does not include GIS topo line overlay)

Gmap4 homepage: http://www.mappingsupport.com/p/gmap4.html

Joseph, the Gmap4 guy
Redmond, WA

Very cool.