Experiences in set-up and usage of a geodetic real-time differential correction network

Abstract

Global Navigation Satellite Systems (GNSS) are commonly used for geodetic and land surveying applications. The stand alone accuracy provided by these GNSS are insufficient for the majority of these operations (GPS, 1995), therefore some form of differential correction method is required. Accordingly, the state survey offices of Germany have installed a differential correction service for geodetic applications. Code- and phase-corrections are broadcast in the VHF-band using the RTCM V2.1 format (RTCM, 1994). One major problem is that the accuracy depends on the distance to a reference station (length of baseline) because of residual orbit and atmospheric biases. To achieve a more precise solution, a number of reference stations are connected together to form a network. Within this network these influences are computed and a set of “area correction parameters” are also transmitted in RTCM message Type 59. Field trials and measurements have confirmed the high accuracy of this service. This paper describes the system itself, investigations of communication methods as well as site planning. In addition measurements from field trials will be presented to demonstrate the high accuracy in a real-time environment.