Tony Nixon
Advanced GIS Assignment #9
November 11, 2013
LiDAR Exercise
In this exercise a specified ground raster is derived from a LAS file to show elevation and contour
lines of an area within DeWitt County, Texas. A TIN, LAS, and Terrain Dataset are also created along the
process. A profile graph was created with the final output from specified 3D points along the ground.
Methodologies closely followed the Evaluating LiDAR Data handout provided.
The methodology used to create the final ground raster and outputs is as follows:
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A geodatabase was created called Lidar to store all outputs.
A feature dataset was created called TerrainData with the same coordinate system and
tolerances as the LAS file.
A point file with information of the LAS file was created to get the basic statistics such as point
count and point spacing.
A new feature class was created of an area of interest to mask all other outputs.
A multipoint features were created from the LAS file using LAS to Multipoint tool. One feature
represented all non-ground points and the other was all ground points only.
A TIN was then created from the bare earth (ground points) multipoint feature using the Create
TIN tool.
The TIN was then used to create a raster using the TIN to Raster tool. This created a raster
representing ground elevation.
Using the 3D analyst toolbar, a line was drawn using Interpolate Line on the ground raster. A
profile graph was then created from the line showing the elevation changes along the line.
Using the 3D analyst toolbar, contours were also created by using the Create Contour tool.
Contours were made along the ground raster by dragging boxes around desired locations.
Using the Draw toolbar and the Convert Graphics to Features option, the contours were created
into contour features.
A final output was created from the bare ground raster, the contour lines, and the profile graph
as shown below.
An LAS dataset was also used to analyze the LAS file to construct contour lines and another
profile graph.
Create an LAS dataset within the Lidar folder where the file exists. Right click the folder and click
new LAS dataset. Rename this dataset LASdataset.
On the new dataset, right click and select properties. On the LAS Files tab click the Add Files
button and select the LAS file. Once this is added, analyze the statistics to know what return
values exist. Click apply and ok to add the files to the dataset.
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Add the dataset to a blank map document and open the LAS Dataset toolbar. Use this toolbar to
create contour lines from just the ground points. Select ground for Filters and Contours. Create
a profile by using the LAS Dataset Profile Tool and dragging an area on the map you want to
create a profile. This output can also be seen below.
A Terrain Dataset was also used to analyze the LAS file to construct contour lines and another
profile graph.
Create a File Geodatabase called LASdbs. Create a Feature dataset called Terrain. Import the
multipoints feature created from the LAS file created earlier. Create a terrain dataset from the
feature dataset.
In the New Terrain window select the multipoints feature and the area of interest feature if
necessary. Use the approximate point spacing determined earlier from the ptfileinfo file. Use Z
Maximum as point selection method with a mild secondary thinning method. Add pyramid
levels as desired and finish dialog.
Add the terrain dataset to map document and use Surface Contour tool to create contour lines
with a 2 meter contour interval. The point profile tool was not working properly in the 3D
Analyst toolbar..