MAPS and GPS COORDINATES:

All maps on "Joe's Guide to Yosemite National Park" use UTM and NAD27 Datum for coordinate display. While there are several alternate standards and systems, I prefer UTM and NAD27 for two reasons:

1. UTM (Universal Transverse Mercator) is a grid-based coordinate system that is much easier to use than degrees/minutes/seconds (although slightly less accurate). Each UTM square on the map equals a square kilometer of territory, so it is quite easy to find your location and estimate distances. Many versions of the USGS topo maps of the greater Yosemite area have the UTM grid (US Zone 11S) drawn in and the National Geographic Trails Illustrated Map for Yosemite National Park also includes the UTM grid.)
2. NAD27 Datum: While NAD83 / WGS84 Datum is more popular in many regions, NAD27 is used by both the USGS topos and the National Geographic Trails Illustrated Map for Yosemite National Park.

If you use any of the maps on this website to help with navigation, please be sure that your GPS unit is using the same settings! If you accidentally have your GPS set to WGS84 Datum, you will appear to be roughly 200 meters off target. The National Geographic Trails Illustrated Map for Yosemite National Park is also highly recommended to give you a complete overview of the layout of the park and the locations of various hikes.

Note: The history and technical details of coordinate systems are quite complex (and will not be explained here!), but many books and websites give laboriously thorough explanations.

Sample Map: