Aspen Hanger


GeoBiking.Org 3G

Satellite III

GPS Limitations:

There are many different types of GPS receivers out there with differing capabilities. I created all of my data in a way that they can even be used on most basic or older units. The GPS does not have to be able to display a map to benefit from this information. The following list reflects my desire to allow widest usability of the trail data.

Waypoints ==> Locations that are manually marked

    • AKA "Points Of Interest" or POI
    • I limit length to 8 characters (any longer and they are hard to read)
    • The first 2 to 4 letters are capitalized and are the same for all waypoints in a route to help group/identify them
    • These first 2 to 4 letters are used as the map key
    • Waypoint comments are limited to 16 characters on older devices
    • There are many different waypoint symbol sets out there. These icon sets may vary even between versions of a GPS model
    • Mapping these symbols between units is problematic
    • Garmin 76Csx symbols are used in files I provide
    • Use my GPXl8r application to translate them for other types of GPS units
    • Lowrance units also have un-named points they refer to as "icons". You can't search for them, but they appear on the map

Routes ==> A group of locations that you visit in a set order

    • Originally I limited to 30 points per route for older Magellan compatibility
    • Most newer models handle 50 or more, but I now try to limit them just for documentation simplicity
    • Route names are limited to 13 characters in length
    • Routes can be traversed in either direction, although waypoint comments may not make sense if you do.

Tracks ==> Automatically recorded points that show where you've been or want to follow.

    • AKA "Bread Crumbs" or "Trails"
    • I limit Track names to 13 characters - (National Geographic limit)
    • Limited to 250 points per track for earlier Garmin units. (Relaxed recently as most units now handle 500)
    • On Garmin units, the active tracklog can hold more points than saved tracks. The track is automatically simplified when saved
    • I've manually tweaked these track points to represent the actual travel as closely as possible
    • Because of the point limitations, they do not follow every twist & turn in the trail, especially on long stretches where you don't have any path options
    • The number of tracks that can be saved on a GPS or viewed at one time varies per GPS.

GPS Accuracy ==> Varies

  • Depends on how well spread apart the "viewable" satellites are
  • Virtually all units made since late 2005 are WAAS enabled, allowing as close as 10 foot accuracy
  • WAAS is less usable the farther North you go in the US
  • Typical estimated position error is in the range of 20-30 feet for most of the spots I mark
  • Heavily wooded/steep areas typically have higher error potential
  • Rock walls can reflect strong signals causing significant errors


Mapped Track Accuracy ==> Varies

  • As indicated above, it varies with the length of trail and how straight the trails are
  • It is usually close enough to let you know which side of a street it was recorded on
  • Larger discrepancies may show on trail sections where you don't have turn choices

Trail Organization:

Colorado Trails are split into several groups to help make working with them more manageable.  I initially split them based on their relationship to the confluence of the Platte River & Cherry Cr.

  • CO_DS ==> Trails that are south of, or water drains ino the Platte River below the Cherry Cr confluence
  • CO_DN ==> Trails that are north of or water drains into the Platte River above the Cherry Cr confluence
  • CO_FN ==> Trails outside and north of metro area. Arbitrary cut: (Boulder/Brighton on to Ft Collins/Greeley)
  • CO_CR ==> Trails in Douglas county south of the metro area e.g. Franktown, Castle Rock, Larkspur
  • CO_CS ==> Trails in El Paso county and S
  • CO_70  ==> Trails along I70 in the mountains

Trail Documentation:

I maintain both text and spreadsheet trail documentation for all of my mapped trails.  Documentation provides route statistics, waypoints, comments, notes and connecting trails.

Spreadsheet format ==> Microsoft Excel

  • Separate sheet for overview and each trail
  • Prints one page per trail
  • Sheets hyperlinked to/from overview page and connecting trails


PDF format ==>

  • PDF version of above spreadsheet - for those w/o excel or don't want to edit information
  • Hyperlinks do not work here


HTML format ==>

  • Separate files for overview and each trail (HTML version of spreadsheet)
  • May print more than one page per sheet
  • Hyperlinks show but do not function


Map Key ==>

  • I use a unique 2 to 4 character abbreviation for each track
  • Key is used on maps to make them easier to read
  • Key is used as the prefix for trail waypoint names
  • Key is used as track & route name to keep things short & simple
  • Key is color coded to track


Color Coding ==>

  • Each trail has a color
  • There are a limited number of colors I use for trails
  • Available track and route colors vary by GPS and mapping or documentation software
  • I try not to have two trails with the same color crossing
  • Color printing can be problematic as colors may not appear as on monitor
  • Some trail colors blend in with background on Topo and others on Satellite imagery
  • Some GPS units allow you to set a color for specific tracks: I try to approximate key color. (Garmin, DeLorme & GPX format only of course, National Geographic is very limited)


GPS formats:

There are a lot of ways to store & transfer the data, I provide these:

GPS Exchange Format: .gpx

  • This is the de facto standard for GPS information exchange, and is a form of XML
  • Many software applications read/write this format, including most manufacturers.

DeLorme Format:.an1, .anr & .pmo

  • Used with their Topo USA & 3D Quad software
  • .an1 stores waypoints, map symbols and track & trail items (also .an2 for Topo NA)
  • .anr stores route data
  • .pmo files are map overlays
  • Since DeLorme started supporting .gpx, I no longer provide routes and tracks for this format
  • I provide a draw layer for each zone of the tracks and waypoint files using PN20/40/60 symbols
  • I now provide a map file that allows the entire trail network to be shown on PN20/40/60 by just copying it.

National Geographic: .tpo

  • Another major consumer mapping contender, very easy to use
  • Not as powerful as DeLorme, so it is much simpler to operate
  • Since they started supporting .gpx, I only provide a file with all tracks for zone in it
  • You can't output track data from this product

Google Earth: .kml or .kmz (compressed)

  • Google Earth also reads .gpx files
  • My GPSxl8r software can output with appropriate symbols & colors

You can use the free GPSbabel software to convert between these and many other formats.

My GPSxl8r software can help maintain track symbol usability between vendors.