GPS vs. Traditional Surveying

Chris Dunn

The Short Answer

The law favors the system in place now.&

GPS is not YET as accurate given the same amount of field time.

GPS vs. Theodolite

GPS vs. Total Station

GPS Satellite Constellation

Both GPS and Surveying use Trigonometry

However GPS does Trig at the speed of light.

Vertical & Horizontal Distance

Hasn’t GPS made conventional surveying obsolete?

With Global Positioning System applications as widespread as they are today, one might wonder why surveyors can’t just enter the coordinates of the property corners into their GPS units to find and/or set property corners.

The most significant practical issue with GPS is that acquiring positioning data of sufficient accuracy and precision for boundary work requires open skies (no trees or buildings) and long occupation times (GPS receiver positioned above the point).

This is usually no problem under the open skies of the Great Plains on large tracts that would otherwise take a long time to survey. However, it is either impractical or impossible on many parcels in the US.

http://www.inlandsurveyingllc.com/faqs.htm

Hasn’t GPS made conventional surveying obsolete?

Real Time Kinematic (RTK) GPS technology can produce positions that are generally within 1”-2” of reality instantaneously.

RTK uses instantaneous correction data from a reference network of GPS receivers with known coordinates (“base stations”) transmitted to a “roving” receiver via cellular modem.

This is much improved over the several yards of potential error in a handheld GPS.

Yet it still isn’t good enough to meet the accuracy standards for boundary surveys, and it still doesn’t work in the woods.

http://www.inlandsurveyingllc.com/faqs.htm

Hasn’t GPS made conventional surveying obsolete?

Another point to remember is that property corners and lines are not defined by coordinates. Nor are they defined by the bearings and distances on a plat.

They are legally defined by the actual on-the-ground location of the original monuments (i.e. iron pins, etc.) that created the boundary line.

Until both the technology and the law change dramatically, conventional surveying is here to stay.

http://www.inlandsurveyingllc.com/faqs.htm

www.gps.govUnlike conventional techniques, GPS surveying is not bound by constraints such as line-of-sight visibility between survey stations. The stations can be deployed at greater distances from each other and can operate anywhere with a good view of the sky, rather than being confined to remote hilltops as previously required.

GPS is especially useful in surveying coasts and waterways, where there are few land-based reference points. Survey vessels combine GPS positions with sonar depth soundings to make the nautical charts that alert mariners to changing water depths and underwater hazards. Bridge builders and offshore oil rigs also depend on GPS for accurate hydrographic surveys.

http://www.gps.gov/applications/survey/

But, wait there is more!

For a set of links on this topic you can go to my website at www.geovelo.org