SHARE2012: Avon
Ground based LiDAR team -
Kerry Cawse-Nicholson, Terence Nicholson, Andy Scott
Date - 20 September 2012


Ground based LiDAR scans were taken of several objects within the site. 
Snapshots were taken of the target, and approximate distance and angle from sensor to target were recorded. 
LiDAR was oriented with the LiDAR head facing the target, so that the scan angle did not begin or end at the target. 


The LiDAR scan name is given without a data format or extension, since several formats are available after processing with the LASprocessor. 
These include: Cartesian and polar co-ordinate text files; LAS files; ENVI images (including header files); PCD; and PLY files. 
Note that an offset exists between the time of scan (real time) and the time of scan recorded in the LiDAR filename. 
The Excel spreadsheet should be used to determine correct time. 


Where distance was recorded, this is the distance to the nearest edge of the target. 
In the case of the scans over Shea's targets, a single tree in the middle of the scene was chosen as a reference point, 
and all measurements are recorded with respect to the reference. Distances and angles were not measured for repeat samples. 


Angles were measured using a compass, where magnetic declination was not taken into account.




Lidar data was collected using the SICK LMS-151 lidar system. 
The SICK LMS-151 lidar system has a maximum vertical field of view of 270º, 
an angular step width of 0.25º and a scanning frequency of 50Hz. 
The instrument is mounted on a rotation stage to provide 360º field of view 
in azimuth at 0.25º step width. 
The lidar beam diverges to give an effective beam size of 15.8cm at 10m. 
The system is then mounted on a tripod and tethered to a computer and power supply, 
which can be carried by the operator in an external frame backpack. 
This allows rapid data acquisition at the rate of 25-scans/half-hour."

The data is available in the following formats: 
Cartesian and polar co-ordinate text files; 
LAS files; 
ENVI images (including header files); 
PCD; 
and PLY (opens in Meshlab) files. 

***Note that an offset exists between the time of scan (real time) 
and the time of scan recorded in the LiDAR filename. 
The Excel spreadsheet in the field notes 'Scan_details.xls' should be used to determine correct time.***