This paper describes the height and planimetric errors of repeated ALS (airborne laser scanning) strips with a deeper focus on building extraction. Measurements with Toposys Falcon airborne laser scanner were arranged in May 2003 in Espoo, Southern Finland. A 5 km test area, consisting of urban settlements and forests, were collected from the altitude of 400 m resulting in measurement density of about 10 points per square metre. One 4 km long and about 100 m wide strip was collected five times allowing the analysis of the repeatability of the laser scanning. One strip was used as a reference and inter-strip comparisons were made. Point wise comparison methods were also used to characterize the differences. Additionally, target models were compared against each other. Real Time Kinematic (RTK) GPS and also tachymeter measurements were used as ground reference. Extraction of building vectors from laser scanner data was performed using interactive methods implemented in the TerraScan software. The accuracy of the vectorization is also reported. Mean height errors for elevation points were –2 to 1 cm and standard deviations were mainly ±3-4 cm. In planimetry, mean errors of the centre points of the buildings were less than 30 cm for the first and also for the last pulse data when compared with the buildings on the map. The standard deviations varied between ±11-28 cm (first pulse) and ±1418 cm (last pulse) for extracted buildings using repeated observations. Mean errors were between 3-8 cm and standard deviations ±36 cm using last pulse data of repeated observations and extracted ridge information. Extracted buildings were systematically larger from first pulse data than from last pulse data.
[1]
J. Hyyppä,et al.
A QUALITY ASSESSMENT OF AIRBORNE LASER SCANNER DATA
,
2003
.
[2]
Thomas Voegtle,et al.
Effects of different laser scanning modes on the results of building recognition and reconstruction
,
2000
.
[3]
Juha Hyyppä,et al.
A METHOD FOR INTERACTIVE ORIENTATION OF DIGITAL IMAGES USING BACKPROJECTION OF 3D DATA
,
2003
.
[4]
Thomas Voegtle,et al.
3D modelling of buildings using laser scanning and spectral information
,
2000
.
[5]
Petri Rönnholm.
THE EVALUATION OF THE INTERNAL QUALITY OF LASER SCANNING STRIPS USING THE INTERACTIVE ORIENTATION METHOD AND POINT CLOUDS
,
2004
.
[6]
S. J. Oude Elberink,et al.
Assessing height precision of laser altimetry dems
,
2002
.
[7]
H. Maas.
Methods for measuring height and planimetry discrepancies in airborne laserscanner data
,
2002
.
[8]
George Vosselman,et al.
Two algorithms for extracting building models from raw laser altimetry data
,
1999
.
[9]
Emmanuel P. Baltsavias,et al.
Airborne laser scanning: existing systems and firms and other resources
,
1999
.