Airborne Scanning

Peter Rieger, Andreas Ullrich: High-Speed High-Density Data Acquisition in Airborne Laser Scanning Applications 31.10.2011

Correctly determining a measurement range in LIDAR instruments, based on time-of-flight measurements on laser pulses, requires the allocation of each received echo pulse to its causative emitted laser pulse. Without further precautions this definite allocation is only possible under specific conditions constraining the usability of range finders and laser scanners with very high measurement rates. Losing the unambiguity of ranges in high repetition systems is well known in RADAR and the term “multiple time around” (MTA) has been coined. However because of fundamental differences between scanning LIDAR and RADAR, with respect to MTA processing, new approaches for resolving range ambiguities in LIDAR are possible. In this paper we compare known and novel techniques for avoiding or even resolving range ambiguities without any further user interaction required. Such techniques may be based upon measures affecting hardware (e.g. spatial multiplexing or modulation of consecutive laser pulses), software (e.g. assumptions about the true measurement range based on a rough DTM) or both hard- and soft-ware in order to achieve a high probability of correctly resolved range ambiguities. Furthermore a comparison of different approaches is given, discussing their specific (dis-) advantages and their current status of implementation.

This paper was presented at SPIE 2011 in Prague and is available in the corresponding proceedings:
Peter Rieger, Andreas Ullrich, "Resolving range ambiguities in high repetition rate airborne LIDAR applications", Proc. SPIE 8186A, 8186A-9, (2011).

The beside mentioned presentation gives an overview of the RIEGL laser scanners capable of echo digitization and full waveform analysis and presents the possibilities using the new RIEGL airborne laser scanning software RiMTA for automated resolution of range ambiguities.