Sharing A Map

CalTopo has three basic modes of operation:

Blank maps do not yet contain any data (markers, lines and polygons), but may contain custom layers. Since the entire map state is stored in the URL, nothing is actually saved to CalTopo's server. A blank map will have a URL of /map.html, possibly with a bunch of extra information, e.g. /map.html#l=39.24625,-120.50348&z=15&b=mbt.


To share a blank map, use the Share this map link in the left bar. The dialog that comes up provides both a URL and an IFRAME snippet you can use to embed the map into another webpage.


Since the sharing URLs are often quite long, you can click on the shorten link in the dialog to produce a shorter URL for easy sharing, e.g. /l/7GHH.

Draft or unsaved maps contain markers, lines or polygons, but have not yet been saved to CalTopo. You can still access most features, including exporting and printing, but your data will be lost as soon as you leave the page.


On draft maps, the sharing link will be replaced with a red "Save this map" link, and the top nav bar also gets a Save option. Clicking this link will bring up a prompt to sign in, or if you're already signed in, the Save As dialog.


For more information on sharing, see below.

Saved maps are ones where the data has been saved to CalTopo. On a saved map, the URL is m followed by a 4-digit code, e.g. '/m/ABCD`, and the Share this map link is back in the left bar.

In a style similar to other online editors such as Google Docs, changes made to a saved map are automatically synced to all other users. If you and a friend are both looking at the same map, any new lines you draw will automatically show up on your friend's computer.


When saving a map, or under the Manage this map option in the left bar, you can control how other people can view or edit your map.


Maps have 3 visibility settings.

  • Completely private maps are only visible to you. Even if someone else knows the map's URL, they will be unable to view it.
  • Viewable with URL maps are accessible to anyone who knows (or guesses) the 4-digit map ID in the URL. This is the default option for all maps.
  • Publicly viewable maps show up on CalTopo's Shared Maps layer, and are indexable by Google. Use this option for map data you want to share with the world.

If you want someone to be able to make changes - such as when planning a trip with a friend - you can set a password in the optional password line. If you do not set a password, the map will remain read-only to everyone but you.

Someone else visiting the map can enter the password as shown below.