Geoscience Reference
In-Depth Information
-x FIRST_RETURN
The location used to index the pulses is set to first return.
-i LiDAR.las
Name of the input LAS point dataset.
-o LiDAR_10m.spd
Name of the output SPD point dataset.
18.2 Classify Ground Returns
Once the SPD file has been created, the next step is to classify the ground returns. We
will combine two algorithms implemented inSPDlib, spdpmfgrd and spdmccgrd
(see Sect. 15.3.5 ) . The second algorithm is only applied to the returns classified in the
SPD point dataset as ground (using the option --class 3 2 ). This can take advan-
tage of the particular strengths of those algorithms. The SPDPointsViewer can
be used to explore the dataset and visually assess the quality of the ground return
classification (Fig. 18.1 ).
Fig. 18.1 Ground returns classified from the LiDAR data using SPDLib and visualised in the
SPDPoints viewer (points in red correspond to ground returns)
2 This deviates from LAS, where class 2 has been reserved for ground.
 
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