Proximity to the Trail

How close to the trail am I? This tends to be a common question whether you're on the trail or sitting at home binge watching your favorite series while self isolating.

Here are several ways you can answer that question regardless of your tech-saviness.

Postholer Google Trail Maps
This is by far the easiest way to find your proximity to the trail, and you have access to a fully interactive map in the process. This requires a device with location services enabled, like a smartphone (Hint: a desktop PC may not work well). Here's how:

• Visit the Google Trail Maps page
• Choose your favorite trail
• Click on the star icon.
• A green marker will appear. Click on it for a wealth info, including your proximity to the trail.

Create a .PNG/.JPG Image
You can create a static image with tons of additional info to suit your taste. This requires a bit of tech-saviness. We'll use Project GIS for this.

• Start with the findNearest layer in the Project GIS documentation.
• You can click the findNearest title for an example.
• For now, leave the 'layers' as it is. You can change 'layers' to any layer(s) available in the project.
• You'll want to specify a 'trail_id'. We'll use the Appalachian Trail, trail_id=3. You can choose from 31 major U.S. hiking trails (and growing). Look for trail_id in the parameters section.
• So we don't unintentionally crop anything, change 'bbox' to the full national map, &bbox=-126,24,-66,50
• Change lat/lon to your location. Lat/lon must be in decimal degree format.
• We'll also specify an image height of 400 pixels, &height=400

So, here's what we have so far:

   http://gis.postholer.com/services/reflect?
      service=WMS
      &layers=stateLines,trace,mileMarker,findNearest
      &trail_id=3
      &bbox=-126,24,-66,50
      &lat=41.752832
      &lon=-124.194178
      &height=400
      &t_srs=EPSG:900913

As a proper URI (no spaces or new lines), it will look like this:
http://gis.postholer.com/services/reflect?service=WMS&layers=stateLines,trace,mileMarker,findNearest&trail_id=3&t_srs=EPSG:900913&bbox=-126,24,-66,50&lat=41.752832&lon=-124.194178&height=400

Plug that into your browser (or just click it) and you should see:

Get it as CSV/JSON
Getting the information textually is almost identical to getting an image. Let's build the URI:

   http://gis.postholer.com/services/reflect?
      service=WFS
      &typename=findNearest
      &trail_id=3
      &srs=EPSG:4269
      &lat=41.762278
      &lon=-124.251570
      &outputformat=text/csv

As you'll notice 'layers' was replaced by 'typename' and it should only have a single value. The full documention for WFS layers can be found in Project GIS.

The complete URI is:
http://gis.postholer.com/services/reflect?service=WFS&typename=findNearest&trail_id=3&srs=EPSG:4269&lat=41.762278&lon=-124.251570&outputformat=text/csv

Plug that into your browser (or just click it) and the resulting file should look like:

   WKT,fid,type,distmiles,distkm,bearingtotrail,yourlocation
   "POINT (-84.198417 34.650986)","1",trail,"2150.5","3460.9","100",41.762278 -124.25157
   "POINT (-124.25157 41.762278)","2",location,"2150.5","3460.9","100",41.762278 -124.25157

The above is for CSV. To get JSON change outputformat to &outputformat=application/json