Using GPS in Geoscience Education
GPS = Global Positioning System
With the advent of 12-channel consumer GPS receivers that are WAAS-enabled (Wide Area Augmentation System ( This site may be offline. ) ), it is now possible to obtain horizontal positions to better than 5 meter accuracy for under $250. A number of WAAS-enabled handheld GPS receivers are available for $150 or less with a horizontal accuracy of about 5-10 meters. The addition of an external antenna to amplify the signals and reduce so-called "backplane reflections" can reduce the error to about 2-5 m. A general rule of thumb is that vertical GPS accuracy is roughly three times the horizontal accuracy.
An often-forgotten feature of GPS is its usefulness as a clock. The receiver clock is updated automatically by the atomic clocks in the satellites. This makes it a highly accurate time resource that can be used with other measurements.
Types of GPS Receivers
GPS receivers can be broken down into two basic classes:
- consumer-grade or handheld receivers ($150 to $600)
- professional grade receivers ($3500 and higher)
Recording GPS Data
Downloading GPS Data to a Computer
Most consumer- and professional-grade GPS manufacturers provide or sell connection cables and software to download GPS data from the receivers to a computer. Since each manufacturer, and often each receiver, uses different communication calls, it is necessary to find software that is compatible with your receiver model. Consumer-grade software will usually export text files that can be loaded into GIS software after some minor editing.
MN DNR shareware extension for Garmin GPS downloads. (more info) -- Works as ArcView extension or stand-alone Windows application. Data can be imported into a variety of projections and exported to text files or ESRI shapefiles.
Windows 2000/XP Note: These operating systems use multi-tasking and multi-threading techniques that can create communications problems with standard serial (RS232) ports. The result is that data may be lost while downloading from the GPS, but with no error messages from the software. One way to bypass this problem (other than going back to a Windows98/ME machine) is to use a Serial-to-USB adapter. These devices allow you to use a USB port on your computer rather than the serial port. The drivers for the device will create a "virtual" serial port that you set in the GPS software. While this will prevent data losses, it will not increase the communication speeds to USB levels. Some newer GPS receivers are using USB connections, hopefully a new trend.
Macintosh Note: Since most GPS receivers communicate over PC serial (COM) ports, there are currently few Macintosh-native solutions (e.g. GPSy (more info) ). However, there are a number of work-around solutions posted online (search "GPS download macintosh" or specify the brand of your receiver), but most report that the configuration of your hardware and operating system greatly influence the behavior of the connection. All seem to require running a Windows emulator and a version of the Windows operating system on your Mac. As newer receivers move to USB connections it may become simpler to connect to Macintosh computers.
Examples of Using GPS in Geoscience Education
- GPS field exercise to trace words in a field to explore GPS accuracy
- Floodplain lab modified to utilize GPS and GIS
- What is GPS? ( This site may be offline. ) - from Garmin
- What is WAAS? ( This site may be offline. ) - from Garmin
- All about GPS (more info) - from Trimble
- GPS Tutorial ( This site may be offline. ) - from Lowrance
- FAA Navigation Programs ( This site may be offline. ) - information about GPS, WAAS, and aircraft navigation
- US Naval Observatory Time Service Dept. (more info)
- US Air Force NAVSTAR Joint Program (more info)
- GPSy (more info) - a Macintosh-native program for GPS communications and simple GIS.
- Herrstrom, E.A., 2000, Enhancing the Spatial Skills of Non-Geoscience Majors Using the Global Positioning System, J. of Geosci. Edu., 48, p. 443.