Lab 5: Creating a Digital Surface Model and Digital Terrain Model from Lidar Data

Goals and Background:

The purpose of the lab was to gain experience in using lidar data. An LAS dataset was explored with ArcMap 10.2.2, and lidar derivative products, such as DSM and DTM, were created. Lidar is a growth industry that has boomed recently due to its useful applications. Skills learned in the lab will serve students well in the workforce.

Methods:

Part 2:

An LAS dataset was created using ArcMap 10.2.2 and files were provided by Eau Claire County (2013). Features of the LAS dataset were explored by viewing the statistics of the data. Statistics were used for a quality check of the data to determine if elevations in the data were accurate to real world data.  Additionally, a shapefile of Eau Claire County (Price, 2014) was added to the LAS data set to determine if the data was spatially correct. The horizontal coordinate system was assigned to NAD 1983 HARN Wisconsin CRS Eau Claire (US Feet), and the vertical coordinate system was assigned NAVD 1988 US feet.

Point clouds were visualized in ArcMap 10.2.2 using the LAS Dataset Profile View tool for a 2D representation of any location in the dataset. The LAS Dataset 3D View tool was used to see the same location in 3D.

Part 3:

Section 1:

A digital surface model (DSM) and digital terrain model (DTM) were created using the LAS Dataset to Raster Tool in ArcMap 10.2.2. The results for the DSM and DTM can be seen in Figures 1 and 3, respectively.

The parameters for the DSM model were:

• Interpolation: Binning
• Cell Assignment Type: Maximum
• Void Filling: Natural Neighbor
• Sampling Type: Cellsize
• Sampling Value Field: 6.56168ft (2m)

The parameters for the DTM model were:

• Interpolation: Binning
• Cell Assignment Type: Minimum
• Void Filling: Natural Neighbor
• Sampling Type: Cellsize
• Sampling Value Field: 6.56168ft (2m)

Hillshades were created for the DSM and DTM images using the Hillshade tool under 3D Analyst Tools. The hillshades for the DSM and DTM can be seen in Figures 2 and 4, respectively.

Section 2:

A lidar intensity image of the Eau Claire area was created using the LAS Dataset to Raster tool. Before the tool was opened, the LAS Dataset was set to Points and the Filter was set to First Return. Once in the LAS Dataset to Raster tool, the following parameters were used:

• Interpolation: Binning
• Value Field: Intensity
• Cell Assignment Type: Average
• Void Filling: Natural Neighbor
• Cell Size: 6.56168ft (2m)

After the image was created in ArcMap 10.2.2, it was loaded into ERDAS IMAGINE 2013 to enhance the display of the image. The intensity image can be seen in Figure 5.

Results:




Figure 1: DSM of Eau Claire

Areas of lower elevation are darker and areas of higher elevation are lighter in the DSM.



Figure 2: Hillshade of Eau Claire DSM

The hillshade of the DSM shows objects on the ground clearly. 

Figure 3: DTM of Eau Claire

The DTM is a bare-earth representation of the Eau Claire area. 

Figure 4: Hillshade of Eau Claire DTM

The hillshade of the DTM does not have any ground objects and is useful for interpreting the bare landscape.

Figure 5: Intensity image of Eau Claire

The intensity image records the strength of the return, and is useful for interpreting lidar data.

References:

Eau Claire County. (2013).

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