Accessing 2011-2012 LIDAR

GIS day 2012Larry Theller

ABEPurdue University

Indiana's Statewide LiDAR data is produced at 1.5-meter average post spacing for all 92 Indiana Counties

Public Download has 50,000,000 point limit – about 4 square miles.

Seven Miles

As a registered user you have 150,000,000 point download.

7 Miles

Points.las

Dems.tar.gz

Google Earth plug-in for viewing

Conclusion

• Out-of-the-box DEMs from OpenTopography do not support hydrologic modeling.

• LAS cloud downloads from OpenTopography will require processing of point cloud downloads into larger data sets.

• Dev blogs suggest LAStools as good software for this.

http://gis.iu.edu/datasetInfo/index.php

Examples

• ArcGIS 10.1 enhanced for LiDAR• Check the ArcGIS 10.1 online help• Be prepared to manipulate VAST

amounts of data.• You need a fast/high RAM computer• Terabytes of disk space….

Floodplain Analysis with LIDAR Data

• Flood extents are typically estimated by comparing models of water surfaces and ground surfaces.

• Water surface profiles for a given flood event (for example, 50-year flood) are created

• Each profile represents the height of water across the river at a given location. The length of each profile is long enough to capture the largest possible flood extent going out from either side of the river.

• Profiles are generated at reasonable intervals along the river where the flooding is being modeled

Each polygon is classified as either ABOVE, BELOW, or EQUAL so you can tell where the modeled water surface is above the terrain dataset. These areas are potentially flooded.

The primary output from the Surface Difference tool is a polygon feature class.

The Surface Difference tool provides an option to output a difference raster. Positive cell values in this dataset represent depth, which is another important piece of information in flood studies.

Tree Canopy Analysis with LIDAR

• Forest canopy density and height are used as variables in a number of environmental applications.

• These applications include the estimation of biomass, forest extent and condition, and biodiversity.

• Canopy density, or canopy cover, is the ratio of vegetation to ground as seen from the air.

• Canopy height measures how far above the ground the top of the canopy is.

• Lidar can be used to determine both of these variables.

ground

canopynoise

Create a LAS dataset and layer

Create a LAS dataset and layer

ground

canopy

noise

Calculating the density

• The most effective way to determine the canopy density is to divide the study area into many small equal-sized units through rasterization.

• compare the number of above ground points to the total number of points.

• The important technique to remember here is to determine an appropriate cellsize for this analysis. It needs to be at least four times the average point spacing.

• You can go larger but not smaller with the cell size.

Observations• Modeling process requires a series of

steps• May be done in Arcgis 10.1• Cell-based analysis divides above ground

hits by total hits to produce above ground density• Surface difference tool needs processed

ground surface…

Above ground density

Canopy height above ground

Conclusions

• Download LAS from OpenTopography for small areas 2- 4 sq miles

• Download (multi-tool) LAS from IU for larger areas

• OT has no useable DEMs for hydrology• Download DEMs from IU or USGS seamless for

hydrology models.• Learn to process LAS files outside of ArcGIS for

point cloud LiDAR analysis

Conservation ModelingGoogle conservation model lidar minnesota