Import ASCII format LiDAR data to SPDLib

It is common to get LiDAR data (from airborne or terrestrial systems) in ASCII format. However, the format of data within the file (which data is in which column, delimiter etc.,) often varies. To account for these differences SPDLib uses an XML scheme to define which data is in which column and the delimiter. There are some example schemas provided with in the ‘schemas’ folder with the SPDLib source

As an example to demonstrate reading an ASCII file into SPDLib, LiDAR data from NERC’s Airborne Research & Survey Facility (ARSF) is available to download from http://neodc.nerc.ac.uk. You just need to sign up for a NEODC account and then apply for access to the ARSF data.

The ASCII lidar files supplied by ARSF are space separated and contain the following columns:

Time, Easting, Northing, elevation, intensity, classification, return number, number of returns for given pulse, scan angle rank

Note: the ASCII files are only used as an example here, ARSF also supply data in LAS format which is recommended for importing into SPDLib

To import the points with associated intensity and classification the following schema is used:

<?xml version="1.0" encoding="UTF-8" ?>
<line delimiter=" " comment="#" ignorelines="0" >
    <field name="X" type="spd_double" index="1" />
    <field name="Y" type="spd_double" index="2" />
    <field name="Z" type="spd_float" index="3" />
    <field name="AMPLITUDE_RETURN" type="spd_uint" index="4" />
    <field name="CLASSIFICATION" type="spd_uint" index="5" />
</line>

This is saved as ‘arsf_ascii_lidar.xml’ and is passed into SPDLib using the ‘–schema’ flag:

spdtranslate -i LDR-BAS13_01-2014-063-20.txt \
             --if ASCII --schema arsf_ascii_lidar.xml \
             -o LDR-BAS13_01-2014-063-20.spd \
             --of SPD \
             -b 2

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