“Can It Keep You From Getting Lost?”

It’s happened to all of us at some time. We’re trying to find our way in an unfamiliar area, and we discover that our maps aren’t up to date. Or maybe our intended route is blocked, and we have to find an alternate route to get to our destination. This happens to foresters, timber cruisers, appraisers, and initial response fire fighters more than we care to admit. It frequently results in lost time, frustration, or making an extra trip on another day.

Fortunately, there is a great solution that will help us navigate easily and quickly to our destination. With the right software and equipment, we can attach a GPS unit to a notebook PC and have our exact location pinpointed on a USGS 7.5 minute quad map at all times.

Excluding the cost of the Notebook PC, the software and equipment can be purchased from $250 to $500 depending on GPS model and USGS quad data set. Real Time GPS tracking requires an inexpensive software and data program such as All Topo Maps, a consumer grade GPS unit, download cable, external antenna, and a power inverter.

With the equipment properly set up, users can track their location on 7.5 minute USGS quad maps as they are driving. The vehicle’s position on the quad maps is updated every 5 to 15 seconds. The location is as accurate as the positioning capability of the GPS unit and the accuracy of the USGS quad maps. Normally, overall accuracy is between 40 and 200 feet. Better accuracy occurs in open areas, less accuracy under dense timber stands.

Position accuracy is exceptional, considering users frequently have consumer grade GPS units. Usually positions are accurate enough for clear determination of which road is being traveled, specific intersections, stream crossings, and major land features.

The new consumer grade GPS units have exceptional capability to track satellites under tree canopy. While they don’t have the accuracy of more expensive field grade GPS units, they are very capable of receiving and tracking the signals under most dense canopy conditions. In the open, some of the new GPS units are capable of three meter horizontal accuracy, especially GPS units capable of receiving the Wide Area Augmentation System (WAAS) correction signal.  Under tree canopy, the error can be as much as 60 meters.

In situations where the user is driving on roads the USGS quads don’t show, the GPS track Log can actually help fill in that information in your GIS system. Data from some models of Garmin GPS units can be downloaded into a PC and then converted into a shape file format for use in ArcView GIS software.  The transformation process is quite easy, and several coordinate formats are supported.  Log onto http://www.atterbury.com for a free Microsoft Word document outlining the procedure to convert Garmin GPS data to a shape file. The ArcView extension is also available for FREE.

The All Topo software and data sets have all USGS quad maps for the entire state. The 1:24000, 1:100000, and 1:250000 maps are available for viewing. Usually, the 1:24000 maps are used, because they show the most detail. The All Topo software will move the GPS cursor automatically as the user drives. When the user drives off the edge of a USGS quad map, All Topo will automatically bring up the appropriate adjacent quad in just a few seconds.

Benefits of using real time GPS tracking:

· Keep track of your location at all times

· Tie GPS coordinates to photos for appraisals

· Help find your destination when using alternate routes.

· Save time

· Create concise track logs to import into ArcView.

Caution!  Be careful while driving. Stop your vehicle in a safe place before viewing the screen. Keep the external antenna in a position that holds it securely and keeps the antenna lead from getting kinked in the door.

Summary:  Using real time GPS tracking in a vehicle can help us be more efficient, save time, and reduce backtracking. Part II of this series will cover using GPS and a Pocket PC in a real time tracking system while walking in the woods.

Sources: All Topo Maps: Atterbury Consultants, Inc. Oregon $88, Washington $80, call (503) 646-5393 for other states. Garmin GPS units: WWW.GPSCITY.COM, recommended model is GPS MAP 76 at approximately $310 or GPS MAP 76s.