birdandhike.com logo
Home | Birding | Hiking | Wilderness | Wildlife | Rock Art | Vegetation | Geology | Backroads | Aircraft
Hiking Around Las Vegas; a hiking guide by Jim Boone

A Note about GPS Coordinates

I provide longitude, latitude, and UTM coordinates to assist people who use global positioning system (GPS) units. I provide longitude and latitude coordinates for roads and trailhead locations because these coordinates are more familiar and are the default system in vehicles. For trails, I provide UTM coordinates because this system is based on a rectangular grid that is more useful for plotting points on maps and calculating distances.

I hike with a GPS unit and record my movements. I then use the GPS data to estimate trail distances, plot points and routes on maps, and determine elevation profiles. My methods are simple and straightforward, but using GPS data, my distances often differ from official maps and other publications. In part, the differences are due to vagaries in the GPS system such as position errors (horizontal and vertical) due to poor satellite constellations, reflections, and obscured views of the sky (e.g., trees and narrow canyons). These errors should produce small differences between my data and published sources, and to some extent I can correct for these problems. In other cases, the differences are due to the rerouting of trails over the years that are not yet reflected on the maps. In these cases, my data can be quite different from published sources.

The default map datum used on GPS units sold in the U.S. is WGS84 because it is modern and more accurate than older datums. However, the local USGS topo maps are based on the older NAD27 datum. Therefore, all of my route descriptions use NAD27 to match the maps. Given the precision necessary to find trailheads, the map datum used for finding roads and trailheads doesn't matter too much. When hiking, however, the two datums differ by about 200 yards around Las Vegas, so you will get close, but not exactly there using WGS84. If you want to match the USGS topo maps and match my printed coordinates, set your GPS unit to use the "NAD27" or "NAD27 CONUS" map datum. See The Problem of Map Datums and USGS Topo Maps for details and an example.

ELIMINATE THE PROBLEM: The best way to eliminate map datum problems is to download my GPS files (GPX format) and upload them to your computer, phone, or GIS unit -- your device will take care of the translation because GPX files are WGS84. My waypoint files can be opened by Google Earth and all other commonly used Waypoint Manager Program.

All GPX files on BirdandHike are compressed using ZIP compression. This is done because when GPX files are downloaded, web browsers often change the file type to XML because, technically, GPX files are XML files. Sometimes web browsers convert GPX files to TXT files because, technically, GPX files are TXT files too (XML files are just TXT files with the text in the file arranged in a particular way). In either case, who knows what to do with an XML or TXT file? In both cases, people would need to change the extension back to GPX. However, most operating systems automatically unpack ZIP files to properly reveal the original GPX files, and that eliminates the problem.

All coordinates and distances presented here are approximate. Although I take care to prevent mistakes, if something seems wrong, assume that I made a mistake and use your own good judgment. Unless otherwise stated, distances "from Las Vegas" are measured from the Spaghetti Bowl (the intersection of Interstate-15 and Highway 93/95).

Note: All distances, elevations, and other facts are approximate.
copyright; Last updated 150517

Birding Around Las Vegas Guide Service Glossary Copyright, Conditions, Disclaimer Home

 

Google Ads