Step One: Save Maps to Your Browser. See this post for details.
Step Two: Cache Map Tiles. Go to http://caltopo.com/togo. You'll get a rectangle select just like on the Print and KMZ Export pages. Choose the area and zoom level you need, and check the layers you want to bring with you.
|layer and zoom selection|
You'll see "Processing . . ." for a while as the server builds up a cache manifest, and then a browser specific progress message. When all the files are cached, you'll get an alert and be redirected to the offline page:
Step Three: Go Offline. When you go offline, or when you just want to take it for a test drive, point your browser at http://caltopo.com/offline. You'll get a simplified version of the CalTopo UI, using the OpenLayers map engine instead of Google Maps.
|The simplifed CT2GO UI|
|The layer dropdown is limited to your cached layers|
Some random thoughts and caveats:
- This will not work with IE (9 and below) as it doesn't support HTML5 Application Caches.
- This feature is both more fragile and harder to test than a standard online webapp. Please send me bug reports if something doesn't work right.
- Tile caching is currently limited to one rectangle at a time.
- While it worked fine with an iPad, phone support is tricky, mostly because of the screen real estate required for the caching page. I'll work on allowing you to draw a rectangle with your desktop and then cache it on your phone.