Good News: The USFS has at long last published data for hiking trails on their GIS server. GIS = Geographical Information System. Displaying this hiking trail data directly from the USFS GIS server has the following advantages:
* This is the same GIS hiking trail data that the Forest Service’s own Interactive Visitor Map displays. http://www.fs.fed.us/ivm/
* Only enough data is downloaded to fill your screen. This is much less data than downloading a file (KML, KMZ or SHP [shape]) with all the trail data for an entire national forest.
* The attribute data for a trail is not downloaded from the GIS server to your screen unless you ask for it by clicking on a trail.

Bad news: So far the only USFS GIS hiking trail data that is available is for the Umatilla National Forest which lies in SE Washington and NE Oregon. The FS also published “centerline” trail data for NV and UT but that thin black line is very hard to see.

I applaud the FS staff at the Umatilla NF for being the first to share their hiking trail data via the FS GIS server. Hopefully more national forests will also publish their GIS hiking trail data sooner rather than later.

Below is a 'live' map that displays this GIS hiking trail data for a random spot in the Umatilla NF. To toggle the trail layer on/off, click the basemap button (it is next to the Menu button). Then in the Overlay column, click the “USFS_trail” layer. Mobile users will need to scroll down to the Overlay section. As you turn the trail layer on/off, note the trails that were not printed on the topo. Perhaps those trails did not exists when the topo map was printed. Remember, these USGS topo maps are scans of actual paper topos.

See more text below the map.



Trail Class

If you look at the map legends (click “About this map”) then you will learn that the symbology for a trail depends on the the trail class. Click on a trail and look at the GIS attribute data to learn a trail’s class. Unfortunately, the attribute data does not give you any way to find out the characteristics that define the different trail classes.

This is an example of one of my biggest gripes about GIS data. It is extremely common for GIS data to be coded (like the attribute value for trail class) and there is no metadata provided that we can use to understand the data that is hidden from view behind the codes. This is even more of a teeth-gnasher once you realize there is a cheap, easy and effective solution.

The FS has a data dictionary document that describes each of the attributes (i.e. fields) of data for each trail record. Alas, that document is only available on the FS internal server. All they have to do is put that document online and then add an attribute field for each trail. The value for that attribute would be a link pointing to the data dictionary. Anyone could then find the definition of trail class in the data dictionary and learn that the allowable values are 1 through 5. The data dictionary could also include a link to the detailed definition of each trail class. I found that definition online and am hosting it on my server. Here it is (2 pages):
http://www.mappingsupport.com/p/recreat ... _class.pdf

GIS Miles

Scroll to the bottom of the attribute display to find this value. Here is a summary of what a FS person told me.

Distance data was collected by the FS engineers for engineering purposes. Each trail is one or more segments. Anytime certain engineering characteristics changed, the current trail segment ended and a new segment began. A segment endpoint might be at a trail junction but just as easily could be in between trail junctions. One segment of a main trail can easily include several junction with side trails.

Well it was certainly a sorry situation that the FS engineering people were apparently not on speaking terms with the FS recreation people. There would have been virtually no incremental cost to also record the distance between trail junctions and if that had been done we all would have vastly more useful distance data.

Those that are curious can compare the following two maps which have the same center and zoom.

Current GIS trail data.
http://www.mappingsupport.com/p/gmap4.p ... tion_1.txt

Beta trail data that I obtained some months ago plus some of my code. If you click a trail the segment endpoints are displayed.
http://www.mappingsupport.com/p/gmap4.p ... atilla.txt

I will ask the USFS to add GIS attributes to each trail segment that will have the starting and ending coordinate for the trail segment. Software can then highlight those segment endpoints on the map so you can see the extent of a trail segment when you click the map.

Date last maintained

Nope, I don’t see any such trail attribute either. Pity.

Rec Area URL

This is another great attribute that is missing from the GIS data. Many Umatilla FS trails have an informative web page that can be displayed with a link like:
http://www.fs.usda.gov/recarea/umatilla ... d=________

For example, the prior two map links are centered on the North Fork Walla Walla Trail #3222. Here is the FS web page for that trail:
http://www.fs.usda.gov/recarea/umatilla ... ecid=57013
This should be an attribute value that is displayed when you click the trail.

Dynamic layers

This is not a trail attribute but instead is a setting on the GIS server. From looking at a large number of GIS servers, my sense is that 99.99% of the time this setting is ‘off’. But it is ‘on’ for the trail data. This should mean that my code can change the styling for how the trail data appears on the screen. I plan to poke at this and see if it really works. At best, the syntax for doing this can be called arcane.

Joseph, the Gmap4 guy