.LAS files (Log ASCII Standard)

• Not useable directly in ArcGIS

• A single X-Y position can have multiple Z values

• Must be converted to MultiPoint file

Zooming in you can see the individual data points that make up the file.

3D Analyst Extension Required

Arc Toolbox > 3D Analyst Tools > Conversion > From File > LAS to Multipoint

Converting LAS files to Multipoint

Terrain constructed in either a File or Personal Geodatabase from the multipoint file

Right click feature data set > New > Terrain

DSM raster and hillshade Terrains cannot be hillshaded or used for raster analysis so a raster is created from the terrain

3D Analyst Toolbox > Conversions > From Terrain >

Terrain to Raster

Use Environments > General Settings > Extent > Same as

Display to limit processing area

Reprocessing for “bare earth”

Last returns can be used to construct a “bare earth” DTM of the scene, removing vegetation and some cultural features such as buildings and cars.

Using the swipe tool in ArcMap allows comparison of the DSM (left) and DTM (right).

Draping orthophotos on bare earth LiDAR

Orthophoto mosaic from NYS orthophotography program with base elevations set to

bare earth LiDAR DTM

ArcScene, part of 3D Analyst extension, allows 3D visualization.

Monitor well locations

Point shapefile from GPS

coordinates of wells with base

heights mapped to LiDAR bare earth

Building the water table surface data set

Extract elevation at well positions from LiDAR DTM using Spatial Analysts Tools

Spatial Analysts Tools > Extraction > Extract Values to Points

Values added to attribute table as RSATERVALU

Add additional fields for water depth in feet, water depth in meters and water surface elevation. Water depths in feet are entered manually, other values are calculated using field calculator.

Interpolating the water table surface

3D Analyst Tools > Raster Interpolation > IDW

Z value is Water_elv

Other interpolation methods can be tried as well.

Surface can be contoured, but best visualization is achieved by adding the surface to ArcScene.

3D rotation in ArcScene allows

the water surface to be viewed from

multiple angles

How close to reality?