Notes on using Google Maps to show hiking trails

I have been working on using Google Maps to show the routes of various hiking trails in my area. It can be done, but it's not very straightforward. Here are cursory notes on what I learned in the process (i.e. this is not a detailed how-to).

Initially I used Google "My Maps." Here are the characteristics of Google "My Maps" relevant to mapping hiking tails:

• Google "My Maps" displays the length of a path when you click on it, which is good for showing people how long a trail is.
• You can upload a GPX track to it by the roundabout method of importing the GPX track into Google Earth and then exporting it from Google Earth as a KML file, which you can then import into Google My Maps. Or you can use the GPS Visualizer web site to convert GPX files to KML files: http://www.gpsvisualizer.com/
• Unfortunately Google My Maps has a limit on the number of placemarks and lines it will display at one time. If you add exceed this number of items Google My Maps will automatically bump some of your items to a second page so that it is impossible to see everything at once.
• Another unfortunate characteristics of Google My Maps is that it apparently has a limit on the number of points that can be in a single line. If you exceed this limit Google My Maps will split the track into two lines of the same color. I searched for a long time and couldn't find any work around. See: http://www.google.com/support/forum/p/maps/thread?tid=7d6964088b224b32&hl=en

There is a workaround to avoid having your placemarks/lines broken up into multiple pages if you have a lot of them. This workaround also gets around long tracks being broken up into multiple lines. You can display a KML file using Google Maps by entering the http address of the KML file in the search box of Google Maps. When a KML file is displayed this way there is apparently no limit on the number of items that can be displayed (or at least the limit is higher). Also, when you display a KML on Google Maps using this method your long tracks/lines will not be broken up into separate lines.

If you don't want to upload a KML file to a web server to display it you can also display all the items of a Google "My Maps" map that has too many items to fit on one page using this trick. Just right click on the View in Google Earth link in My Maps to get the http address of the KML file, and then enter that in the search field in regular Google Maps. I have seen forum postings that some people have had problems with this, so posting a KML file to a web server may be the most reliable approach.

I decided to go with uploading my KML file to a web server and then searching for its URL in Google Maps. Once I that I faced the choice of whether to continue to use Google My Maps to edit my KML and then export the KML file, or to use Google Earth to edit the KML. Although both Google Earth and Google My Maps are awkward to work with if you have a lot items, I decided to go with Google Earth.

The problem with using Google Maps to render a KML file is that you don't get distance measurements on the length of lines. I decided to work around that by uploading my KML to Google My Maps and then clicking on tracks/lines there to find out the distance. There is also this hand web site that will tell you the length of a Google Earth track/line: http://www.emaltd.net/google/gec/utilities/index.asp?l=en

How to download KML data from Google My Maps

I had put a lot of time into a particular custom map under Google "My Maps" and I wanted to make an offline backup of the data. I clicked on the "View in Google Earth" button when viewing my Google "My Maps" map and it downloaded a KML file which I could open in Google Earth. However, when I opened the KML file in a text editor I saw that it didn't contain any actual map data but instead just had a http URL pointing back to Google Maps. After some experimentation I discovered that I could download the actual map data by taking the URL from inside the downloaded KML file and changing each instance of "&" into plain old & and then pasting the edited URL into my browser address bar. This returned a real KML file with real data.

Incidentally, you can display a KML file on Google Maps by uploading the KML file to any webserver and then putting the http address of the file in the Google Maps search box and hitting enter. Google maps will then display the KML file placemarkers and paths on Google Maps.