Abstract
Abstract. Airborne laser scanning (ALS) is a widely spread operational measurement tool for obtaining 3D coordinates of the ground surface. There is a need for calibrating the ALS system and a test field for ALS was established at the end of 2013. The test field is situated in the city of Lahti, about 100 km to the north of Helsinki. The size of the area is approximately 3.5 km × 3.2 km. Reference data was collected with a mobile laser scanning (MLS) system assembled on a car roof. Some streets were measured both ways and most of them in one driving direction only. The MLS system of the Finnish Geodetic Institute (FGI) consists of a navigation system (NovAtel SPAN GNSS-IMU) and a laser scanner (FARO Focus3D 120). In addition to the MLS measurements more than 800 reference points were measured using a Trimble R8 VRS-GNSS system. Reference points are along the streets, on parking lots, and white pedestrian crossing line corners which can be used as reference targets. The National Land Survey of Finland has already used this test field this spring for calibrating their Leica ALS-70 scanner. Especially it was easier to determine the encoder scale factor parameter using this test field. Accuracy analysis of the MLS points showed that the point height RMSE is 2.8 cm and standard deviation is 2.6 cm. Our purpose is to measure both more MLS data and more reference points in the test field area to get a better spatial coverage. Calibration flight heights are planned to be 1000 m and 2500 m above ground level. A cross pattern, southwest–northeast and northwest–southeast, will be flown both in opposite directions.
Highlights
A permanent test field for airborne photogrammetric systems was established in 1994 (Honkavaara et al, 2008) and a test field for mobile laser scanning (MLS) was initiated in 2009 (Kaartinen et al, 2012) by the Finnish Geodetic Institute (FGI)
After MLS data collection, the scanner trajectory was computed with Waypoint Inertial Explorer software, using GNSS reference data downloaded from Trimnet GPS/GNSS web service
As a first step the street points were extracted to be used by the National Land Survey of Finland (NLS) for their Airborne laser scanning (ALS) calibration
Summary
A permanent test field for airborne photogrammetric systems was established in 1994 (Honkavaara et al, 2008) and a test field for mobile laser scanning (MLS) was initiated in 2009 (Kaartinen et al, 2012) by the Finnish Geodetic Institute (FGI). Airborne laser scanning (ALS) is a widely spread operational measurement tool for obtaining 3D coordinates of the ground surface. A permanent test field for ALS provides means for that and FGI is developing such a field using MLS. The test field has a wide selection of buildings and roof structures: residential areas with detached houses and blocks of flats, industrial buildings etc. Building areas are surrounded by trees and forests, and the ground elevation difference within the test field is about 70 meters. As test field environments and structures are subject to change, and do change, regular updating procedure is required to ensure that the reference data and test data are comparable
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