The threats imposed by the ongoing climate change become successively more clear. In the municipality of Sandviken the possible rise in water level in the lake Storsjön might cause major problems. This study aims to produce an elevation model over one of the threatened areas so that the effect of different water levels in the lake can be studied in the future.
The area of study consists of an esker cutting straight through the lake Storsjön. The area is densely populated and the size is about 13 hectares.
Measurements were performed, both with GPS, utilizing Network-RTK, and with total station. The formations of the ridge were captured by following the breaklines with a point density of 225 points/ha as an intended goal.
The GPS measurements were transformed into the local coordinate system of Sandviken municipality. The measured coordinates for six control points were compared to the true coordinates. The fit was not perfect, so a Helmert transformation was performed on the plane coordinates.
The accuracy of the measurements was below 50 mm after the transformation. Net adjustments in plane and height were performed on the total station measurements. The error ellipses for the station points varied from 2 to 44 mm. The over all point density achieved was 274 points/ha.
Two elevation models were created, one Triangular Irregular Network (TIN) and one interpolated model using a kriging interpolation. Contour lines from both models were produced and compared with each other.
The TIN creates a more angular surface and therefore the contour lines are not as smooth as in the interpolated model. Both models showed good resemblance compared with the original data.
Source: University of Gävle
Author: Bring, Hedda