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How to Figure Acreage With a GPS Unit

GPS technology has numerous applications both for personal and commercial use. A GPS unit receives satellite signals and provides real-time location data. This information can then be plotted onto maps using geographic information system (GIS) software for additional applications and interpretations. Several factors affect the accuracy of the GPS data. Land features such as tree cover or hilly terrain can interfere with satellite signals. Also, a GPS unit measures distances between points "as the crow flies" and does not factor in changes in distances due to topography. For best results, minimize whatever factors you can control.

Things You'll Need

GPS unit
GIS or mapping software
Calculator

Instructions

- 1
  Begin by setting a waypoint at your starting location. A waypoint is a user-defined location marker. The waypoints you collect will determine the boundaries of the site. Refer to your user manual for instructions.
- 2
  Set up the GPS unit's tracking function. The tracking feature is like a breadcrumb trail that will automatically set points along your path of travel. The user manual will contain instructions for setting the distance between points. For greatest accuracy, choose shorter distance intervals, especially if the boundaries are irregular.
- 3
  Walk or drive around the perimeter of the site. Do not veer from the boundary as all data are being captured by the GPS unit's tracking feature. Some GPS units include area calculation on the fly. Refer to the user manual.
- 4
  Stop the tracking feature once you have returned to your starting point. Alternatively, you can create a route. Some GPS units allow you to create and save routes. The difference between a track and a route lies in the ability to use a route again.
- 5
  Upload the GPS data to your GIS or mapping software. Manufacturers such as Garmin offer mapping software that is compatible with their GPS units. Refer to the software instructions. Note that some software programs may require that you specify the type of data that will be uploaded. Be sure to include waypoint and track or route data with the data exchange.
- 6
  Use the area function on your mapping software to calculate the area of the site. Alternatively, manually calculate the area if your software does not include area function. Use the distance tool to manually select the points along the length of the property. Note this figure.
- 7
  Determine the property's width by the same method using the distance tool. Multiply the two figures to calculate the site's area. Convert square feet to acres by using an online calculator. Be aware that this figure is just an approximation.

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