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Global Positioning System

We use two Leica satellite receivers to fix positions on the earths surface. These are newer units, allowing us to use two different technologies to perform our tasks:

  1. RTK: using the RTK (Real Time Kinematic) survey process, we are able to 'carry' and read out coordinates, in real time in the field, accurate to within one centimeter, plus or minus 2 parts per million. Using an fm radio signal which broadcasts a correction from the base receiver, the rover unit is free to roam up to 6 miles away, in any direction, with this high degree of accuracy. Multiple observations bring precision into the picture.
  2. ORGN: the Oregon real-time GPS network consists of CORS (Continuously Operating Reference Stattions), operated by the Oregon Department of Transportation and other public and private entities. Using cellular technology, a correction signal is received at a rover receiver, and the corrected position is displayed and stored if needed. You can read more about the ORGN at https://www.oregon.gov/ODOT/ORGN/Pages/about-us.aspx.

We still employ conventional surveying tools (theodolite, Electronic Distance Measuring, compass, tape, etc.) when working under a tree canopy. We also do verification checks of G.P.S. measurements using conventional technology on occasion. As you can see, G.P.S. is a high-tech tool, which, if properly used, can lend both speed and accuracy to our work. Traversing literally dozens of miles in one day is now done by a 2 person crew using G.P.S. equipment, whereas the same work, done to the same degree of accuracy and precision using only conventional tools and methods would take the same crew up to several times as long.
We plan to use the positional information in the county's Geographic Information System in the not-too-distant future.
For more information about the G.P.S. system in general, visit the U.S. Coast & Geodetic website.

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