Lab 5: LiDAR Remote Sensing

Goals and Background:

The goal of this lab is to be introduced to working with LiDAR data structure and processing.  Surface and terrain models along with an intensity image will be created from LiDAR point clouds.  Working with LiDAR data and the LAS file format is important because it is a growing field in the industry and is an important skill set to have.  

Methods:

To begin working with LiDAR data, a LAS dataset was created in Arccatalog from a file of point cloud data.  This dataset was then imported into Arcmap.  Using the metadata from the point cloud data the LAS dataset was assigned a horizontal and a vertical coordinate system.  Using the LAS toolbar in Arcmap, filters, and other options can be manipulated to view the data in different ways.  Elevation, aspect, slope and contour are all options that the data can be viewed in.  An interesting tool that is available in Arcmap is the LAS dataset profile view tool.  This allows the user to select a area of interest and view it like they were standing on the ground next to it.  This example is looking at a bridge. 

LAS Dataset Profile View Tool

Next a Digital Surface Model and a Digital Terrain Model were created from point clouds.  To do this the LAS dataset was converted into a raster in Arcmap by using the LAS dataset to raster tool and using the maximum value as the input value.  This raster image was then turned into a digital surface model by running it through the hillshade tool.  This created a surface model that includes buildings and vegetation. 

Digital Surface Model

To create the digital terrain model the same thing was done with the point cloud data except this time minimum was used as the input value to make the raster image.  This made the image use the data that was closest to the surface of the earth. This digital terrain model is of the ground in the area of interest. 

Digital Terrain Model

The last image that was created from the LiDAR data was an intensity image.  This was done using the same LAS dataset to raster tool but this time using intensity as the value.  This image is like a optical image but without the visible bands. 

Intensity Image

Results:

 The resulting images that were created can be used in a variety of different ways.  The digital terrain and surface model can be overlaid on each other and a swipe tool can be used to look at them at the same time.

Swipe tool in Arcmap

This can be useful if the effects of water drainage and water flow wanted to be examined.  The user could look at the terrain model and determine where the water would flow without any vegetation or buildings.  The surface model could then be looked at to see how it would influence the water after the general flow from the terrain was already determined.  This could be very useful when trying to plan emergency water drains for the city.  

Sources:

Eau Claire County. (2013).

Price, M. (2014). Mastering ArcGIS 6th Edition. Mastering ArcGIS 6th Edition Dataset [shapefile]. New York: McGraw Hill