Projekta „Viena centimetra precizitātes Latvijas ģeoīda modelis GNSS mērījumiem” 2.etaps (01.12.2014-31.03.2015.)

Information on existing and necessary GNSS/leveling data sources was gathered. Summarized information on those leveling points which have both leveling data and coordinates obtained by GNSS. Selective verification of existing data by GNSS measurements was performed.

To achieve more homogenous coverage of the points which have leveling and GNSS data on heights the additional GNSS measurements (four hours long) were performed on those points which had only leveling data.

GNSS measurements were performed on N1 and N2 points across the whole scheduled area, measurements continue. Zenith telescope is being prepared for field measurements to make possible measurements at the remote areas, especially across the border of Latvia, where any information is absent.

GNSS data is being processed by two different GNSS post processing software (Bernese GPS software v5.0 and Topcon Tools v8). The coordinates are computed using LATPOS reference stations in LKS-92 coordinate system and using EPN reference stations in EUREF coordinate system. LKS-92 coordinates are transformed to ETRS89 using Helmert transformation as well as EPN coordinates are reduced to ETRS89. Findings are being analyzed and the publication is prepared.

Data output file for geoids model computation is being prepared and current approximation is carried out. It is expected that there will be many such approximations to make possible systematic quality check of the new incoming information of the increasing data set.