High Accuracy Reference Networks: A National Perspective

High Accuracy Reference Networks have been, or are being, established in a large number of states. These networks consist of stations spaced at 25 to 100 km intervals, whose positions relative to the NAD83 reference coordinate system and to one another are known with much higher accuracy than is the case with the existing network. These upgrades to the National Geodetic Reference system are being undertaken to meet expressed user needs for greater accessibility and higher accuracy in the horizontal reference network in the era of the Global Positioning System {GPS). The increased use of kinematic and pseudo-kinematic GPS field methods and fixed, automated reference stations, which lend themselves to direct GPS positioning relative to a single reference network site, as well as three dimensional positioning, will make High Accuracy Reference Networks increasingly important in the future. The National Geodetic Survey is working closely with surveyors in states to provide the fundamental coordinate system, to support survey planning, observations, and data reduction, and to integrate the High Accuracy Reference Networks and the existing network to assure compatibility. The establishment of a High Accuracy Reference Network throughout the United States in the next few years seems inevitable. The question to be answered is how to achieve this result as rapidly and efficiently as possible.