LiDAR Lab 1

Report

Please provide a written report with the following:

1) One to two sentence description of the LiDAR area you chose, and why. Please include screen shots from your PC of the area in your lab report.

2) Include the code you used for generating the surface models from FUSION and other code from LASTools. If you used the GUI instead, include screenshots of your selected processing options.

3) A two to three sentence description of the analysis you performed on the derivative outputs, i.e. What did you do with the data? Please, include screen shots.

4) In your written report demonstrate you completed at least two of the following lab options:

5) A two to three sentence description of the results you accomplished with screen shots. 

Part 0: Software Installation

This is already done for you on the Lab Machines. If you wish to install on your personal PC follow these directions:

FUSION

Version Check / Software download

Fusion was one of the earliest open-source softwares to be specifically designed to work with forest LiDAR data. It is still one of the most useful software available for batch processing large quantities of LiDAR data.

Fusion's utility is it's command line batch processing feature. Because batch processes can be complicated we'll stick to the basics of surface model generation for the lab.

LASTools

• Download and install the latest version of LAStools.

• Copy the LASzip.dll file into the FUSION folder (file is saved in directory \LAStools\LASzip\dll).

  •  this will give you added functionality of working with LAZ format files in FUSION.

LASTools is an advanced software for editing point cloud data - it has numerous 'free' tools, but the higher end production level tools (for making DEM-models) are licenced for purchase.

CloudCompare

Download newest stable release.

CloudCompare has some other dependencies which you may need to identify on your machine and install.

CloudCompare is a handy viewer, with other powerful processing capabilities for working directly with point cloud data.

Optional Software

OSGEO & QGIS

Download the OSGEO4w package for Windows (or Mac or Linux). Download QGIS

The OSGEO ecosystem comes with GDAL, SAGA, GRASS which are powerful GIS analysis tools. SAGA-GIS can work directly with LAS data.

Part 1: Get Data (15 minutes)

1. Go to the OpenTopography.org website.

   1. If you would like, go ahead and register yourself. This will give you access to expanded areas and larger download sizes.

2. Select an area with available LiDAR data.

   1. Download as LAS or LAZ

   2. Download Ground or All Points.

3. Select derivative layers that you wish to also generate from the LiDAR point cloud 

4. Example Jemez-River Snow-on vs Snow-off LiDAR survey

5. Save the files to an easily accessible folder space.

Part 2: FUSION demo workflow (1 hour)

FUSION Manual with detailed explanations of command line options

2.1 Filtering data (10 minutes)

First we want to run the FilterData function to remove outliers (points like birds, or airborne debris which are far above the ground level).

Example below, using data which are in a State Plane coordinate reference system, units in feet, I use the outlier function for points within a 30x30 foot area where points that register as being outside the 5th standard deviation of the z-axis are removed.

2.2 Digital Surface/Elevation Model generation (10 minutes)

Next, I create a digital surface model using the GridSurfaceCreate function at 3 foot resolution. FUSION generates a Digital Terrain Model (DTM) file. 

Before generating a Bare Earth Model several considerations should be made before leaving the point cloud environment:

• Will the data need any interpolation - such as smoothing or filtering?

• What is the best neighborhood size of the smoothing or filtering?

• Do you want to keep the local maxima/minima?

2.3 Canopy Height Model (10 minutes)

Canopy height models (CHM) are generated when you difference the bare earth elevation from the maximum elevation of the pulses [for our models we used 2 ft canopy height model resolution.

When running CanopyModel you must establish whether you want a canopy surface model [units in elevation above mean sea level], or a canopy height model 35 [units in elevation above bare earth].

Here is an example, of the script we used to generate the canopy height models:

In this example we used the bare earth model we generated from GridSurfaceCreate specified by the /ground switch. 

2.4 Converting DEM, DSM, or CHM to an ASC or TIF file (5 minutes)

Because the DTM format is not consumed by programs like ArcGIS, GRASS, or QGIS you will need to convert the model to a more readily available format. FUSION can convert the DTM to an ASCII file or to a GeoTIFF. 

or

2.5 Change detection analysis: Creating a DEM of Difference (DoD) or a Canopy Height Model (10 minutes)

If you've chosen an area with more than two LiDAR datasets you can attempt to generate a DEM of Difference or DoD.