The best way to learn to use CalTopo.com is to play around with a new map. Unlike some topo programs, the map viewer doesn't have modes that lock the cursor into a single function (line draw, elevation profile, etc.). Instead, you create new objects and modify existing ones by right-clicking on the map background to bring up a context menu. Objects are saved as you work on them; there is no need to explicitly save your data.

Browser Support

All major browsers (IE, Firefox, Chrome, Safari) are supported by CalTopo, although older versions may not work properly. If you encounter a bug, please email me. Printing is the one exception; CalTopo allows you to make borderless prints at any size you want, but your browser may not cooperate. Tested browser support is as follows:

• Chrome: Fully supported. Borderless prints require selecting "Print using system dialog" rather than Chrome's built-in chrome://print page.
• Firefox: Will add a sizeable margin and the page's URL to a printout, so there is no way to do borderless prints. You can still set the page size at 8.5x11 and Firefox will automatically scale it down.
• Internet Explorer: Will print the base map, but will not print shapes or UTM gridlines. I'm working on a solution that involves using OpenLayers instead of Google Maps.

Credits

CalTopo is built on numerous open source libraries, and the map interface powering the site is open source as well; you can download it from the Sarsoft Google Code site. Icons are open source and derived from the Open Icon Library (http://openiconlibrary.sourceforge.net) and http://mapicons.nicolasmollet.com. The freely licensed Javascript code at http://home.hiwaay.net/~taylorc/toolbox/geography/geoutm.html was instrumental in getting me started converting between lat/long and UTM. Magnetic deviation code was based on the Android project's GeomagneticField class. Datum transformations are based on the Abridged Molodensky formula.