Background:

The main goal of this assignment is to give the student a background working with Lidar data. The data provided for the class  was a Lidar point cloud in LAS file format. There were two tasks the students had to complete by the end of the lab. The first task is learning the processing and retrieval of various surface and terrain models. The second task was creating an intensity image from the Lidar point cloud.

Methods:

For this particular assignment, the class was instructed to use ArcMap instead of ERDAS Imagine. The first step was to create a new LAS dataset within our class folder. This newly created dataset will be the data used during the duration of the assignment. Once the dataset was created, the LAS files had to be imported into the new LAS dataset. After all the data was imported, the student analyzed the statistics and metadata to learn which projection the Lidar data was collected.

The next step was to explore the data a little further. In order to do so, the student had to enable the LAS Dataset Toolbar. Once the toolbar was active, the elevation, slope, aspect and contour lines could be shown from the point cloud data. After these tools were explored, the student then learned how to filter out which returns were being shown in ArcMap.

The first Lidar data product to be created was a digital surface model (DSM). This model is the first returns of the Lidar data. Typically it includes tree tops, buildings or houses. When creating this model the pixels were created to be 2 meters by 2 meters. Once the DSM was created, a hillshade was then created. The hillshade from the DSM allows for easier image interpretation.

The second Lidar product to be created was a digital terrain model (DTM). This model is the bare earth returns. It could include first returns if the only return was off the ground surface, but more than likely, it encompasses returns after the first. Once the DTM was created, a hillshade was created with the same guidelines as the DSM.

The last task was creating an intensity map of the Lidar point cloud. An intensity map shows the strength of the pulse that generated a particular point. This map was created using the same tools as that created the DSM and DTM. The only difference was changing the value field to INTENSITY in order to map the intensity. Once this map was created, it was then exported into a TIFF file to be shown in ERDAS Imagine. The reason for showing it ERDAS Imagine instead of ArcMap was becuase the image appears dark within ArcMap.

Results:

Figure 1. This is a hillshade model of the digital surface model (DSM) created within ArcMap
using Lidar point cloud data. 

Figure 2. This is a hillshade model of the digital terrain model (DTM) created within ArcMap
using Lidar point cloud data.

Figure 3 This is an intensity map of the strength of the return for each individual point.

Sources:

Eau Claire County, 2013.

Mastering ArcGIS 6th Edition data by Margaret Price,

2014.