Global Positioning Systems
In the days before Global Positioning Systems, surveyors had to traverse the entire boundary of a parcel, measuring angles and distances along the way. A clear line of sight was necessary between all measured points, forcing surveyors to cut lines of sight through thick brush in order to complete the survey. This method is still in use by some surveyors today.
Voelkel Land Surveying uses a combination of the "old" surveying style, known to surveyors as "conventional surveying," along with Global Positioning Systems, or GPS, to complete most surveys. GPS is the single biggest advance in surveying technology in the last twenty years. With GPS, surveyors no longer have to have lines of sight around the entire boundary of the parcel. With GPS, only a semi-clear view of the sky is necessary to measure points.
A GPS receiver calculates its position by measuring the distance between itself and three or more GPS satellites. Measuring the time delay between transmission and reception of each GPS radio signal gives the distance to each satellite, since the signal travels at a known speed. The signals also carry information about the satellites' location. By determining the position of, and distance to, at least three satellites, the receiver can compute its position using trilateration. Receivers typically do not have perfectly accurate clocks and therefore track one or more additional satellites to correct the receiver's clock error.
Survey-Grade GPS receivers can be used to position survey markers, buildings, and road construction. These units use the signal from both the L1 and L2 GPS frequencies. Even though the L2 code data are encrypted, the signal's carrier wave enables correction of some ionospheric errors. These dual-frequency GPS receivers can have positioning errors on the order of one centimeter or less when used in carrier phase differential GPS mode.
Voelkel Land Surveying has used GPS technology since 1995.