Notes about coordinates, datums, and accuracy. Revised June 12, 2001.
Manual Entry of Coordinates: You can use the coordinates of peaks and enter them manually into your GPS receiver if you do not have the computer interface. This is fine for a few peaks, but will be quite tedious and prone to error for more than just a few entries. For manual entry I suggest looking at the files for the list of interest. Use Wordpad to bring up the list and read the data. The
peaks are arranged alphabetically by name so look down the right side names for the peaks you want then enter the six letter identifier, the zone, and the easting and northing values into the GPS receiver. The easting value always has a leading zero as shown in this list. You do not need to enter the longer name for the peak, the identifier is sufficient.
Datum Notes: The UTM coordinates are to be used with
your GPS receiver set to NAD 27. When you load the waypoint files
with a computer interface the datum used is in the header so the
GPS receiver knows how to use them. If your GPS is set to WGS
84, which is usually the default setting, Garmin receivers will
convert the coordinates to that datum. The only peak not in NAD
27 is Mauna Kea in Hawaii which is in the Old Hawaiian datum.
The only peak list not in UTM is the Munros list which is in Latitude
and Longitude using WGS84 datum.
Accuracy Note: The coordinates of the peaks have been carefully measured from the relevant 7.5 minute topographic maps by hand to the nearest 10 meters or using a computer program such as Maptech which shows the coordinates of the cursor to the nearest meter. The summit or peak as shown in the Peak List is the one measured which may not in some cases be the named summit. The USGS states that the horizontal accuracy is within 1/50th of an inch for 90% of the points on a map. At 1:24,000 scale, (7.5 minute map) 1/50th of an inch is 40 feet or 12.2 meters. Since Selective Availability is now off I have been checking the coordinates in the lists at the summit when I climb a peak. If there is an error of 5 meters or more I save the position and then when I get home enter the correction into the lists. Without Selective Availability the horizontal accuracy when using your GPS should be +/- 5 meters.