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Newest developments in laser scanner technologies put surveyors in the position to comply with the ever increasing demand of high-speed, high-accuracy, and highly reliable data acquisition from terrestrial, mobile, and airborne platforms. Echo digitization in pulsed time-of-flight laser ranging has demonstrated its superior performance in the field of bathymetry and airborne laser scanning for more than a decade, however at the cost of somewhat time consuming off line post processing. State-of-the-art online waveform processing as implemented in RIEGL's V-Line not only saves users post-processing time to obtain true 3D point clouds, it also adds the assets of calibrated amplitude and reflectance measurement for data classification and pulse deviation determination for effective and reliable data validation. We present results from data acquisitions in different complex target situations.

Commission VII, WG VII/7 ABSTRACT:Airborne laser scanning (ALS) is a widely used technique for the sampling of the earth's surface. Nowadays a wide range of ALS sensor systems with different technical specifications can be found. One parameter is the laser wavelength which leads to a sensitivity for the wavelength dependent backscatter characteristic of sensed surfaces. Current ALS sensors usually record next to the geometric information additional information on the recorded signal strength of each echo. In order to utilize this information for the study of the backscatter characteristic of the sensed surface, radiometric calibration is essential. This paper focuses on the radiometric calibration of multi-wavelength ALS data and is based on previous work on the topic of radiometric calibration of monochromatic (single-wavelength) ALS data. After a short introduction the theory and whole workflow for calibrating ALS data radiometrically based on in-situ reference surfaces is presented. Furthermore, it is demonstrated that this approach for the monochromatic calibration can be used for each channel of multi-wavelength ALS data. The resulting active multi-channel radiometric image does not have any shadows and from a geometric viewpoint the position of the objects on top of the terrain surface is not altered (the result is a multi-channel true orthophoto). Within this paper the approach is demonstrated by three different single-wavelength ALS data acquisition campaigns (532nm, 1064nm and 1550nm) covering the area of the city Horn (Austria). The results and practical issues are discussed.

Small-footprint airborne laser scanners with waveform-digitizing capabilities are becoming increasingly available. Waveform-digitizing laser scanners seize the physical measurement process in its entire complexity. This leads the way to the possibility of deriving the backscatter cross section which is a measure of the electromagnetic energy intercepted and reradiated by objects. The cross section can be obtained by firstly decomposing the echo waveform in several distinct echoes, whereas for each echo its range, amplitude and width are known. Then the radar equation can be used for calibrating the waveform measurements using external reference targets with known backscatter cross sections. The final outcome is a 3D point cloud where each point represents one scatterer with a given cross section and echo width. Using these physical attributes and various geometric criteria the point cloud can be segmented or classified. In this paper this procedure is demonstrated based on waveform measurements acquired by the RIEGL LMS-Q560 sensor. The cross section of the homogenous reference targets is estimated with a RIEGL reflectometer and Spectralon® targets.

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