Cofrin Center for Biodiversity

Planning GPS Field Work

The constellation of GPS satellites is always shifting. The result is that anywhere from 4 to 12 satellites may be visible to a GPS receiver at a given place and time. For our natural resources work at UW-Green Bay, satellite visibility is seldom an issue. For those rare situations where satellite visibility could affect the success of a field session, we can use Trimble® Planning Utility to check it out in advance.

Step 1 - Download And Install Planning Utility

The program is available from the Trimble® Planning Software download page. It has also been installed on the Ecodata Drive.

Step 2 - Make Sure A Current Almanac File Is Available

Almanac files (.alm extension) are kept on the Ecodata Drive at Q:\GPS\Trimble\ as shown above. If possible, the date of the almanac should be within 2 weeks of the field work date. If a more current almanac is needed, it can be downloaded from the Trimble® GPS Data Resources website. Right-click on the "GPS/GLONASS almanac..." selection and use "Save Target As" to copy it to a local hard drive.

Step 3 - Start And Configure Planning Utility

Start the program by clicking on the file "planning.exe". The illustration above shows the location of "planning.exe" for those who want to run it from the Ecodata Drive. Once the program is running, a number of configuration settings are required.

First, verify that the utility is looking at the correct almanac. If not, use "Almanac - Load" to direct it to the correct one.

Second, use the Station Editor ("File - Station") to set the station name, position and time of the planned fieldwork. Note that the program uses the terms "station" and "city" interchangeably. Either way they are referring to the location for which the user is seeking planning information. The station list on the Ecodata drive has been modified to include locations frequently visited by UWGB researchers. The stations specific to UWGB are listed first.

Last, uncheck all of the satellite systems except "GPS".

Step 4 - Display Planning Information

Once you've configured the program, you can generate more information than anyone could ever use. The outputs that appear to be most useful are the Number of Satellites graph and the Position Dilution of Precision ("PDOP") graph. 8 or more satellites with PDOP less than 3 generally indicates adequate conditions for field work. The examples below are for October 18, 2009. By coincidence the number of satellites drops down to 4 briefly. Anyone trying to do field work at that time would have been going crazy. Luckily it's a pretty rare occurrence.

Biodiversity Topics: Introduction . Plants . Animals . Mammals . Birds . Reptiles & Amphibians . Arthropods . Spiders . Insects