Lab 5 - LiDAR

GOAL AND BACKGROUND

The goal of this lab was to explore the lidar analysis tools within ArcMap. This included projecting LAS (LiDAR) data and using tools to extract data.


METHODS

Projecting LAS data included reading through the metadata to determine the coordinate system and assigning it to the data.

The data was then projected in ArcMap and adjusting the symbology to show elevation and to show the TIN surface. The contour surface was also explored. To use contours without buildings, a filter was used to only show ground points.

The profile tool was also explored. This tool involves drawing a line through the study area and all points along the line are shown. An example of this is shown in the results section.

The last tools explored were extracting DSM and DTM image rasters from the data. These are shown in the results section. First an image of first return points was created. A hillshade tool was then applied to the image to make it easier to read it as a three-dimensional image.

Next, another image raster was created, this time with ground points only. This meant all structures in the data were not included. Once again hillshade was used on the result. This result was much smoother, since it lacked the structures from before that created a rough texture and abrupt changes in elevation.

Lastly, an intensity image was generated, which showed the intensity of returns.


RESULTS

Shown below is the result of using the contour option with only ground points. The options for which points could be selected are shown on the right of the screenshot.

An example of the profile tool is shown below. A line is visible in the LiDAR data across residential houses, and all points within the line's buffer are shown in the tool window.

The first returns images are shown below. First is the original result, followed by the image with the hillshade affect applied. The abnormalities in the water features is caused by the high absorbance of water, resulting in very low point density. Noise points in these low-density areas tends to create the distortion that appears in the image.

Below are the results from the ground-only images. First is the original image, followed by the image with the hillshade applied. Notice that the image is much smoother with the absence of buildings.

Lastly, the intensity image that was generated is shown below.

SOURCES

Department of Planning and Development. Eau Claire Point Cloud. Collected 2013, May 13.