How to Use Handheld GPS Units to Measure Acreage
By Fred Decker
GPS navigation devices can do a lot more than steer you between Point A and Point B. Depending on your model and its features, they can also help you avoid traffic jams, lead you to the most stunning view in a state park, or measure the acreage of a piece of land. Your GPS not as accurate as a professional surveyor for calculating acreage, but it's still useful as a quick reference. Some models will perform the calculation for you, otherwise you can do the math yourself.
Garmin GPSMAP 62
Ensure that the Garmin has fresh batteries, and take it outdoors. Turn on the unit, and wait while it acquires a satellite signal. A question mark will flash on the screen until the satellites are located.
Travel to the area you want to measure. From the main menu, select "Area Calculation" and then "Start."
Walk around the edges of the area you want to measure. The GPS will record your position periodically, tracking the distance you've walked in each direction.
Tap "Calculate" on the handheld's menu. If the area measurement is expressed in a unit other than acres, press "Change Units" and then "Enter." Select "Acres" as your unit and then press "Enter" again to view the result.
Set your handheld to start a new track. For example on a Magellan Explorist 310, you'd press "Back" from your map screen, and select "Start." Confirm that you want to clear the current track and start a new one.
Walk the perimeter of the area you want to measure. When you're finished, view the track on your map and write down its measurements.
Calculate the area of a square or rectangular property by multiplying its length by its width. For example, if the area is 600 feet deep and 80 feet wide, the area is 48,000 square feet. For a triangular property, divide that area by half. To measure oblongs, polygons or other complicated shapes, divide them into rectangles, triangles or half-circles and calculate the square footage of each portion separately.
Divide square footage by 43,560, the number of square feet in an acre. In the example given previously, 48,000 square feet equals approximately 1.1 acres.
- The specific instructions and menu choices for other handheld GPS models with the area calculation feature will vary, but the overall process is similar. In essence, it boils down to measuring the track, calculating the area and then selecting acres as your unit of measurement.
- Aside from Garmin's GPSMAP 62 series, several other models in the GPSMAP, GPS, eTrex, and Dakota series offer the area calculation feature. So do almost all models in Magellan's Explorist line of handhelds.
- A number of online calculators provide area calculations, based on measurements you enter.
- If your handheld GPS doesn't include the area calculation feature, its companion software -- such as Garmin's BaseCamp or MapSource -- typically does.
- GPS area calculations are not accurate enough for legal purposes, and this type of measurement is not an adequate substitute for a professionally-conducted property survey.
Fred Decker is a trained chef and certified food-safety trainer. Decker wrote for the Saint John, New Brunswick Telegraph-Journal, and has been published in Canada's Hospitality and Foodservice magazine. He's held positions selling computers, insurance and mutual funds, and was educated at Memorial University of Newfoundland and the Northern Alberta Institute of Technology.