Making Field Maps and Marking Locations. How to use a GPS. Garmin etrex Vista. Goals. Build a base map for reference. Locate places so they may be found again. Navigate with confidence to a known point. Add location references to an existing map. Basic Equipment.
How to use a GPS
Garmin etrex Vista
Build a base map for reference
Locate places so they may be found again
Navigate with confidence to a known point
Add location references to an existing map
“Garmin” GPS (plus batteries)
Computer with a serial port
Serial cable for the GPS
Mapping software (e.g., GARtrip)
Scanner (optional: your own base maps)
GPS map (optional: commercial maps)
Single points that you choose
Waypoints assembled into a set
Set of points automatically generated by the GPS
Signal time to arrival
using multiple satellites
4 satellites minimum
Works worldwide, equally well everywhere
Signal is degraded by vegetation cover
Signal is blocked by buildings
Signal goes through a windshield or airplane window, but not the roof of a car or sides of an airplane
Base-Station Differential Correction
~ m to cm
29 satellites in orbit (8/01)
Orbits are not synchronous
Garmin GPS listens to 12 max at a time
Quality of the constellation varies
Controlling the GPS Functions
Coordinate format: hddd.dddddº
02 05 06 09 11 12 14 17 22 27
Initial GPS Acquisition
May take several minutes to get enough satellites
No signal detected
Signal strength of confirmed satellite
Current location and the direction you are moving
US Cities (general) and Foreign (general)
Foreign (some detail)
Some foreign countries (mostly Europe)
01 hrs 34 min
(direction you are moving)
Time of Day
Logging a Track
Use GARtrip to manage your data
Go to the field with the locations of key places already in your GPS
Save sets of location data as separate files
Mark locations of places that are important and carry the GPS so you can find them
Check the batteries before you start
Clear out old data (use GARtrip)
Enter key waypoints (e.g., airports, cities)
Press and hold the “click stick” in (~3 sec)
Waypoint is stored with number for its name;
Link this number to your field notes
Download to GARtrip using the serial cable
Save these waypoints in a file on the PC
Edit the waypoints by adding descriptors
Draw a map with the waypoints
$30 per license
2-way data transfer
Make sure your waypoints are loaded.
Highlight a waypoint and click Edit.
Name: 6 characters max (no spaces)
Description: 16 characters max
Scan (or digital photograph) an appropriate map (max 150 DPI). North up.
Save the scan as a GIF file (or convert to this format).
Inside GARtrip, open with Map/Calibrate
Note: You need to know the GPS location of two places on the basemap.
The basemap will be used as a background for your data.
Scan or digitally photograph a campus map that will be used as a background. Save this as a GIF file on the PC.
Check the GPS with GARtrip to make sure that there are no stored waypoints or tracks.
Check that the GPS has adequate batteries and the setup is proper.
Start the GPS and make sure that it is functioning properly.
Walk the perimeter of the campus, marking the corners on the GPS. You will need two of these points to calibrate the map.
Go through the interior of the campus marking at least a dozen significant points. Record the importance of each point in your notes.
Download the waypoints and tracks into the PC
Edit the waypoints by adding short comments to each one.
Group the campus boundary waypoints as one route and the significant points as another route. Save these as separate files.
Generate a map using your significant points.
Calibrate the map inside GARtrip using two of your perimeter points.
Add your significant points to the basemap.