Topografinių duomenų bazių , sukurtų stereofotogrametriniu būdu, taškų altitudžių tikslumas

Abstract

Vilnius Gediminas Technical University Geodesy Institute has been creating a basic geoinformation topographical database (TDB) of Vilnius city by stereophotogrammetric approach since 1996. The digital city map has been compiled using computerised analogic instalment, autograph A8 carrying out steroedigitisation of photogrammetric model. Aerial photography was made by Norway AO “Fjellanger Widerøe” using aerocamera RMK TOP (ck =153,6 mm) and kinematic GPS. Scale of aerial photography is 1:6000. An investigation of topographical information accuracy of created databases was carried out. In the paper [2], data of accuracy in planimetry of created digital map on TDB are presented. By geodetic field measurements there was detected that mean square errors of bright, well defined contours position regarding to city GPS network are from 0,26 to 0,34 m. In this paper data of point elevation accuracy investigated on TDB are presented. The relief has been constructed by steroedigitisation with regard to the height points. An investigation of height point accuracy on TDB was carried out partly doubling early created TDB as well as comparing height points on TDB with digitised elevations of the same points and involved in TDB or directly identified on the city plans at a scale of 1:500 (total 932 points). Results of control investigation are presented in Table 1. Mean square discrepancies of elevations have been received from 0,10 to 0,20 m. Effective determination of elevation accuracy was carried out by technical levelling TDB contour points recognised on the territory (184 points). Mean square discrepancies of point elevations determined by levelling and photogrammetric approach were received 0,14 m, when maximum discrepancy is 0,40 m (Table 2). Histograms of gained discrepancies (Fgs 1, 2) are presented and as analysis of coincidence of normal distribution was carried out. High accuracy of TDB point elevations (0,15%o of flying height) as well as the closest accuracy requirements, when contour interval is 0,5 m, were approved.