Introduction

The Danish Road Directorate, part of the Ministry of Transport and Energy, is responsible for the management of Denmark’s National Roads that carry almost 30% of the country’s total transport volume. The Construction Unit undertakes maintenance of the existing network, including rebuilding, and the construction of major, as well as smaller, new roads and this requires highly accurate and detailed surveys, specifically measurements of elevation. Current survey techniques, for example manual surveying of control points using Total Stations, are slow not to mention dangerous due to the traffic on existing highways.

3D Laser Mapping were asked to provide a demonstration of the StreetMapper system by scanning Frederikssundmotorvejen, a 3km dual carriageway just outside Copenhagen. The results from StreetMapper were compared against control points gathered by the Danish Road Directorate.

Data Capture

StreetMapper was driven at an average speed of 45kph down each lane of the highway. To comply with Danish highway law, traffic management assistance (TMA) was used that consisted of a vehicle driving behind StreetMapper with a large warning sign.

4 laser scanners were used in total, with 1 pointing down at 20 degrees, 1 up at 20 degrees, and 1 to either side at 45 degrees. This arrangement allowed StreetMapper to achieve an average density of 200 points per square meter on each of the driving lanes.

8 satellites were visible at the start of the survey, rising to 10 at the end of the survey.

Estimated Accuracy

The average INS position RMS (the difference between the forward and reverse TERRAoffice trajectory calculations) was 20mm in elevation and 15mm and 10mm for northing and easting respectively.

Measured Accuracy

Signalised control points were present every 200m in the emergency lane. These had been surveyed by static GPS and levelled with precision alignment levelling.

The edges of the driving lanes were also surveyed using total stations with an RMS of better than 0.01m.

The elevation of the laser data was compared to both the static GPS and total station control points. An RMS of 10mm and 12.4mm and standard deviation of 10mm and 12.3mm was achieved by StreetMapper compared against the static GPS and total station control points respectively.

Results

Images and Animations

Please click on the links below to view images and animations of the data collected by StreetMapper.

Intensity coloured point cloud image

Intensity coloured point cloud image

Intensity coloured point cloud image

Intensity coloured point cloud

Resolution 640x480 Length 29 secs Codec XVid (click to install) Size 79 MB