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Title
Technical Commission VII

International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B7, 2012
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia
4. CONCLUSION
This paper presents a wavelet-based detector to detect the
responded echoes in LIDAR waveforms. Some simulated
waveforms with noises are made to test the limitation of the
detector. The detector treats an echo as an effective return only
if its SNR exceeds a threshold. The experiments suggest that a
weak echo can be detected as long as its SNR is greater than 16
dB. Normally an echo has SNR lower than 22 dB will be missed
in the online process of an ALS. The experimental results also
show that the detector can resolve two distinct scatters as long
as the echoes are separated with a distance larger than the range
resolution of the ALS. In addition to the analysis on simulated
data, the detector has also been applied to a set of waveform
data captured with Leica ALS60 for a forested mountainous
area. In addition to the total number of echoes provided by the
instrument, the detector increasingly found 18% more of the
original number of echoes. This result shows the ability of the
proposed detector in finding weak and overlapped returns from
waveforms. These extra echoes can potentially be used to
improve the estimation of canopy height and ground surface for
a forested area.
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