LiDAR Data Delivery Contents
This page describes the file formats and delivery structure used in the LiDAR data deliveries.
Delivery Structure
A standard delivery directory contains the following sub directories:
- bin - Contains useful post-processing applications
- pt_cloud_filter - Windows and Linux versions of software to remove classified points from ASCII files.
- dem - Contains a Digital Elevation Model suitable for use with APL hyperspectral processing software.
- doc - Contains a copy of the most recent data quality report.
- flightlines - Contains the processed LiDAR point cloud data.
- logsheet - Contains a logsheet that gives a brief overview of the flown project
- navigation - Contains the sol file (post-processed trajectory file)
- screenshots - Contains JPEG files of level-3 processed data including mosaics.
Digital Elevation Model
The format of the delivered Digital Elevation Model (DEM) is band Sequential (BSQ) ENVI format binary data. There is an accompanying ASCII text header file containing the required information to read the binary data. In most cases, the LiDAR data will have been 'patched' with ASTER data. This will extend the coverage of the DEM which is often required for processing the hyperspectral data. There are usually 2 DEMs delivered:
- One projected in WGS-84 Latitude / Longitude
- One projected in the same projection as the delivered LiDAR data (Ordnance Survey OSTN02 if a UK flight or UTM if non-UK).
The DEM projected in WGS-84 latitude and longitude, with heights relative to the WGS-84 spheroid, is suitable for use with the APL hyperspectral processing software.
ASCII LiDAR Point Clouds
The processed LiDAR data are delivered in multiple formats. One such format is as an ASCII list. These point cloud files contain a space separated summary of the data for each point, with each point being described on a separate line of the file. The ordering of the point data is described here. The files can be opened and viewed in any simple text reader but because of their large size this may not be appropriate. It is possible to import these data in to GIS systems such as GRASS or ENVI.
LAS LiDAR Point Clouds
The processed LiDAR data are delivered in multiple formats. One such format is as LAS files. These are currently delivered by ARSF-DAN in two possible formats depending on whether full waveform data has been collected or not. The LAS files are binary data files that have a series of headers and then a collection of data points. They are the standard data type for storing LiDAR data. They can be read by most GIS systems that process LiDAR data, or using the various free software libraries such as LASTools and libLAS.
LAS v1.0
These LAS files are delivered by standard and do not have the capacity for storing waveform data. Detailed information about LAS 1.0 can be found in this document: http://www.asprs.org/a/society/committees/standards/asprs_las_format_v10.pdf
LAS v1.3
These LAS files are delivered only if full waveform data has been collected. Detailed information about LAS 1.3 can be found in this document: http://www.asprs.org/a/society/committees/standards/LAS_1_3_r11.pdf
Navigation
The sol file (a Leica binary format file) contains the post-processed navigation data (position and attitude of the aircraft reference point). Information about the file format can be asked for if required. A python script is available to read the sol file. For full waveform deliveries there may also be TerraSolid TRJ files for each LAS file. The binary file format can be found in the TerraScan user guide available here: http://www.terrasolid.com/download/tscan.pdf
Screenshot images
The screenshots are supplied as JPEG images. This is a type of compressed image format that can be opened by most image viewers. The supplied screenshots include one of the DEM and one of the LiDAR intensity values. If the flight is in the UK and one where Ordnance Survey licensing allows, the intensity image will contain vector overlays to show the expected accuracy of the geocorrection.
Read-Me, Logsheet and Data quality report
The documents included with the delivery are in PDF. This is an open, platform independent standard for distribution of documentation, which allows graphical, text and tabular data to be included in the same file. Free viewers are available for displaying these documents. Please note that these documents will contain important information relating to your data set and should not be ignored.