Spectra-precision Survey Pro v4.5 Recon and Nomad User Manual Manuel d'utilisateur télécharger pdf (Page 220)

User’s Manual – GPS Mode

210

¾ A description of using Ground Coordinates on a reference

mapping plane.

¾ A description of geoid modeling and how to use geoid models

for vertical transformations.

RTK and Post Processing

Using GPS for precise survey measurements requires data from two

receivers to be collected simultaneously. There are two common

methods for calculating positions with this data: Real Time

Kinematic (RTK) and post processing.

In an RTK survey, at least one receiver acts as a base station,

collecting GPS measurements and broadcasting the raw data over a

modem link such as a radio, cell phone, or an Internet IP connection.

The other receiver acts as a rover, receiving the base data and

combining it with its own measurements for a real time solution of

position at the rover.

The rover receiver can get the base data from a single base station

setup in the field, or from a computer server delivering the base data

over the Internet. Base data delivered over the Internet can use one

of two methods: Single base, or Virtual Reference Station (VRS).

Using data from a single base over the Internet is essentially the

same as using a base station setup in the field. In this case the rover

receives data from a single base station and calculates its RTK

position where the expected precision is a function of the distance

between the rover and the base. Using data from a VRS involves the

network software calculating corrections from multiple base stations

in the network. In this case, the rover receives data corrected for

systematic errors and can calculate its RTK position with a precision

similar to short baselines, even though the real distance to the base

stations may be quite long.

In a post processing survey, two or more receivers log raw GPS

measurements simultaneously to a file in the field. Then, the data is

downloaded onto a computer where the differential solution is

calculated (post processed) after the field data collection is completed.

Survey Pro can control GPS receivers for RTK, RTK simultaneous

with post processing, and post processing only data collection.

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Spectra-precision Survey Pro v4.5 Recon and Nomad User Manual Manuel d'utilisateur Page 220