GPS/GNSS Solutions

Survey Control with GPS Reference Stations

Surveyors depend on access to accurate control points for their work. These control points have traditionally been in-ground monuments whose coordinates were regularly updated using conventional surveying techniques by agencies such as the National Geodetic Survey in the United States, l'Institut Geographique National in France, Instituto Graphico Nacional in Spain and Geographical Survey Institute in Japan. The cost to perform regular surveys has increased and the budgets of agencies have decreased. In addition, surveyors have begun to rely more heavily on GPS for their surveying. In response, national and state agencies are increasingly providing Continuously Operating Reference Stations (CORS) for control. The data from these receivers are archived on central server computers so that surveyors can access them for use in their work. The government maintains the coordinates of these stations. This reduces the need to send crews to the field to re-survey the in-ground monuments. In addition, when the crews are sent out they are increasingly using GPS to re-survey these ground monuments. This approach is increasing the accuracy of many control networks while reducing the cost to maintain the networks.