WORKING WITH LIDAR DATA IN ARCGISGEOG3920—Remote Sensing Seminar (Lidar)

University of Denver, November 9, 2010

OUTLINE

Data Information Importing lidar data into ArcGIS Processing options in ArcGIS Software Challenges Software Advantages Software Recommendations

DATA SOURCE

Center for Lidar Information Coordination and Knowledge (CLICK) website (USGS)—http://lidar.cr.usgs.gov

Download .las file format from ArcIMS Server

METADATA

Flying Height: 1000 mPulse Rate: 30 KHzLaser Foot Print: 0.9 mVertical Accuracy: 30 cmPoint spacing: ~1.5 m Nominal pulse density: < 1 mRecorded up to 4 returnsFile Size: ~840 MBNo Classification Code or Return Number Information

INTENDED DATA LOCATION

Mountainous region in Washington between Snohomish and Chelan counties

Or so I thought….

Projection Error CLICK: SPC WA North (4601) Metadata: SPC WA South (4602)

ACTUAL LOCATION Ag Land near Yakima, WA

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READING THE DATA IN ARCGIS

Import steps1. View at .las information2. Convert .las to multipoint3. Extract area of interest4. Use multipoint file in geoprocessing or display functions

.LAS POINT FILE INFORMATION

.LAS TO MULTIPOINT

Can extract all data or by return number or classification code

Can extract with attributes

CLIP TO AREA OF INTEREST

Reduces file size Reduces processing and

rendering time Requires creating a new

feature class and editing Uses Clip tool

AOI

APPLICATIONS FOR LIDAR IN ARCGIS

DEM or DTM (Bare Earth) Extract last returns (LAS to Multipoint Tool) Create mean raster (Point to Raster Tool)

DSM (Surface) Extract first returns (LAS to Multipoint Tool) Create mean raster (Point to Raster Tool)

Contouring and slope analysis Spatial Analyst Toolbox

Terrain Dataset—TIN combining multiple input features Forest canopy height and density

DEM, DSM, and Geoprocessing Tools Intensity Images

Return number and intensity attribute to raster

EXAMPLES

Point to Raster Minimum

Missing Data Values

Spatial Analyst Hillshade

Terrain (TIN) Lidar only

DEM (POINT TO RASTER TOOL)

Missing Data

SPATIAL ANALYST TOOLBOX

Derived DEM products

15 foot contours slope

TERRAIN DATASET—TRIANGULATED IRREGULAR

NETWORK (TIN)

No missing data, Scaled pyramids

MORE ON TERRAIN DATASETS

File Format within a Feature Dataset

Can include multiple types of data for integration Point clouds, break lines, land

classifications, etc.

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EXAMINING CANOPY HEIGHT AND DENSITY

Requires Classification Codes Height: ‘Minus’ Geoprocessing Tool on DEM’s and DSM’s

created from different LAS to Multipoint conversions Density: Point to Raster Tool and multiple Geoprocessing

Tools (IsNull, Con, Plus, Float, Divide, etc.)Canopy DensityCanopy Height

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INTENSITY IMAGES

Load intensity attribute for first return data (LAS to Multipoint Tool) Binary Large Object (BLOB) format Values not directly readable

Mean intensity raster (Point to Raster Tool) Image display requires adjusting stretch and contrast

Intensity Image example from ArcGIS Help

SOFTWARE CHALLENGES

Cannot view 3D point cloud Cannot clip .las file directly Import steps not straight forward Must know return information or class codes Cannot directly view elevation or intensity attributes Dense point spacing = slow rendering, long processing Export options/interoperability Cannot edit points manually

EDITING POINT CLOUD

Terrain Dataset thinning by Z-tolerance (TIN) Thinning by pyramiding (TIN) Raster smoothing (Terrain to Raster Tool)

Nearest Neighbor or Linear, Set cell size

No manual editing options

1:1000 1:300

SOFTWARE ADVANTAGES

Combine lidar with other terrain data to create surfaces Create detailed surface products Perform statistics and spatial analyses Integrate lidar derived products directly into spatial

databases and datasets Can handle heavy processing loads Lidar products in distributable format

Web services Multi-user databases

SOFTWARE RECOMMENDATIONS

ArcGIS is best for processing lidar data according specific user-defined needs

ArcGIS is not an appropriate software for viewing lidar data in 3D

ArcGIS is not efficient for data exploration

ArcGIS should be used to create products for use with other applications