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National Geodetic Network

Extensive triangulation works were started already in the beginning of the 19th century, most remarkable ones being meridian arch measurements by W. Struve, trigonometric measurements by F. Schubert and triangulation works by General C. Tenner.

The modern National Geodetic Network, measured exclusively by GPS technique, is divided into first order, second order and densification networks according to the classification of geodetic networks in Estonia. The base points for the Network are ITRF96 frame points. The density of the Network is 1 point per 225 km² and these form a basis for densification networks. The average distance between adjacent points is 70-110 km in the first order and 15 km in the second order network with the number of points in networks being 13 and 199, respectively. The first and second order geodetic networks were completed in 1998 and are the densification of EUREF network in Estonia (results of the EUREF-Estonia-1997 campaign). The RMS of the points in the first and second order networks is ± 1 cm and relative errors are 1:700000 and 1:500000, respectively.

IAG EUREF Commission (Praha 1999) has classified the Network to conform the requirements of the European Reference Frame Class B and the Network is a densification of EUREF network in Estonia (EUREF-Eesti 1997).

Figure 1. I and II order National Geodetic Network.

The final Network consists of 15 692 GPS vectors, the network is adjusted in two parts - in mainland Estonia and in West-Estonian islands. Adjustment is based on I and II order network points. The software Global X•Positioning System by Inpho Technology OY was used in computations.

Figure 2. I and II order National Geodetic Network and Densification Network.

Re-measurement of National Geodetic I Order Network

A campaign to re-measure the I order geodetic network was carried out between July 28 and August 8, 2008. The campaign took place simultaneously on all I order points (12 altogether) and on all permanent GNSS stations which were operational at that time (7 altogether). The measurement period varied from 108 to 156 hours depending on the point. Measurement methods were similar to those used in the EUREF-Estonia 1997 campaign.