2. Presentation Overview
Project Goals
Guidelines
History of LiDAR
LiDAR in ArcGIS
Comparison of LAS Dataset Vs. Terrain Dataset
Code Structure
Final Output
Conclusion
Questions
3. Project Goals
The goal of this project was to determine if
ArcGIS 10.1 could be used to assess the
accuracy of LiDAR Data
The accuracy was measured against eight
statistics:
95th Percentile
95 Percent Confidence
Average Residual
Minimum Residual
Maximum Residual
Average Magnitude
RMSE
Standard Deviation
4. Guidelines
ASPRS Standards:
95 Percent Confidence no greater than
24.5 centimeters
95th Percentile no greater than 36.3
centimeters
USGS Standards:
Percent grade of slope no greater than 10%
5. History of LiDAR
LiDAR: Light Detection and Ranging
Conceptually been around since 1676
Technology and processing came around
in the 2000’s
ArcGIS 9.3 (released in 2008) was the first
to introduce LiDAR capabilities
6. LiDAR in ArcGIS 10.1
First accepted in two formats: ASCII and
LAS
Need to convert to a multipoint feature
Version 10.1
Introduced LAS Datasets
Added ability to view in 2- and 3-
Dimensional formats
Version 10.2 changed little, but increased the
efficiency of the LAS Dataset to handle larger
sets of data
7. LAS Dataset
Does not import the data, stores
reference to the data’s location
Need a license for either 3D Analyst or
Spatial Analyst
Can view the data in 3-Dimensional
format
Profile view available
The purpose is not to analyze the data, but to
check the quality of the data
Requires data to be classified
Limited to 1-2 million points per LAS file (up to
100 MB in version 10.1)
8. LAS Dataset Continued
LAS Dataset toolbar allows for different
visual techniques
Point Display: Elevation, Class or Return
Surface Analysis: Elevation, Aspect, Slope
and Contour
Need to convert to another format to perform
analytical operations
9. Terrain Dataset
Contained within a Geodatabase and
stored as a Feature Class within a Feature
Dataset
Should use a projected coordinate system
It is a multiresolution, triangulated irregular
network (TIN)
Surface is generated on the fly in the form
of a TIN
Although similar to a TIN, it does vary from
a TIN
10. Terrain Dataset Continued
Terrain Dataset TIN
Can be stored in a Geodatabase Cannot be stored in a Geodatabase,
rather it is stored directly on a disk
Maintains the connection to the
source data/measurements from the
data it was created with
Once it is created the tie to the
original source data is lost
Has no size limit Recommended to have only a few
million nodes, but has a maximum
limit of 10-15 million nodes
Cannot be visualized in 3D using
ArcScene (can use ArcGlobe
though)
Can be visualized in 3D using
ArcScene
Is edited by modifying the source
measurements
Is edited by modifying the
triangulation
* Derived from Esri Virtual Campus Course (Managing LiDAR Data Using Terrain Datasets
11. Code Structure
The Script tool requires two input features:
The surface to be used
Can be Terrain, TIN, DEM, etc. (Anything that
contains elevation information)
The file containing check point information
Other features of the tool:
Sets the workspace for the outputs
Prompts for a name of the output table
Choose fields containing orthometric height
values and geoid separation values
12. Prepare
Outputs
Is the LiDAR Data in Orthometric
or Ellipsoidal Heights
Orthometric Ellipsoidal
Calculate
Ellipsoidal Height
of Check Points
Calculate
Residuals
Generate Absolute Residual
(Used in some Statistical
Calculations
Generate Statistics and Add
to Final Output Table
If the ‘Remove’ Field of the
Check Point Data is Empty
14. Conclusion
Can display LiDAR data using LAS
Datasets and Terrain Datasets
LAS Dataset is good for visual quality
control, but not analytical operations
Terrain Datasets can be used for analysis
and to help answer questions
Although ArcGIS can perform some tasks
on LiDAR data, it cannot be a
replacement for software like Terrasolid
