GIS/MEA582: Geospatial Modeling and Analysis

This is an unmaintained course material, please see current material at:

Geomorphometry I: Terrain Modeling

Resources: ESRI virtual campus Create the folder 'Modeling'.
Download the Raleigh 2013 lidar data as LAS file LAS tile 0793_016 in NC State Plane Meters and the orthophoto to the Modeling folder. Unpack the package containing orthophoto

Bring lidar data into ArcGIS

There are multiple ways of handling lidar data in ArcGIS and improvements are being added to new version of the software. We will follow the step by step, not automated workflow. For other workflows refer to the FYI section at the end of the assignment

Analyze bare earth lidar data

Create a Multipoint flie from .las point cloud

Turn on the 3D Analyst Extension
Menu -> Customize ->Extensions...
Open the ArcToolbox (if not already open)
Select '3D Analyst->Conversion->From File->LAS to Multipoint'
Set 'Input' to 'tile_0793_016_spm.las'
Set 'Output Feature Class' to '.\Modeling\lidar_be'
Set 'Average Point Spacing' to '0.5'
In 'Input Class Codes' type '2'
Set 'Coordinate System' to 'NAD_1983_StatePlane_North_Carolina_FIPS_3200' (you can type 32119 in the search window)
Click 'OK'

Compute a raster map representing number of points per cell (at 2 different resolutions)

.
Calculating for 2m x 2m cell:

Open the ArcToolbox
Select 'Conversion Tools->To Raster->Point to Raster'
Set 'Input Features' to 'lidar_be'
Set 'Value field' to 'Z'
Set 'Output Raster Dataset' to '.\Modeling\bin_count2m'
Set 'Cell assignment type' to 'COUNT'
Set Cellsize' to '2'                            
Click 'OK'

Calculate for 6m x 6m cell:

Open the ArcToolbox (if not already open)
Select 'Conversion Tools->To Raster->Point to Raster'
Set 'Input Features' to 'lidar_be'
Set 'Value field' to 'Z'
Set 'Output Raster Dataset' to '.\Modeling\bin_count6m'
Set 'Cell assignment type' to 'COUNT'
Set Cellsize' to '6'                             
Click 'OK'

Compute raster maps representing different elevation statistics for each cell

Compute mean:

Open the ArcToolbox (if not already open)
Select 'Conversion Tools->To Raster->Point to Raster'
Set 'Input Features' to 'lidar_be'
Set 'Value field' to 'Z'
Set 'Output Raster Dataset' to '.\Modeling\bin_mean6m'
Set 'Cell assignment type' to 'MEAN'
Set Cellsize' to '6'                            
Click 'OK'

Compute range:

Open the ArcToolbox (if not already open)
Select 'Conversion Tools->To Raster->Point to Raster'
Set 'Input Features' to 'lidar_be'
Set 'Value field' to 'Z'
Set 'Output Raster Dataset' to '.\Modeling\bin_range6m'
Set 'Cell assignment type' to 'RANGE'
Set Cellsize' to '6'                            
Click 'OK'

Compute variation (standard deviation):

Open the ArcToolbox (if not already open)
Select 'Conversion Tools->To Raster->Point to Raster'
Set 'Input Features' to 'lidar_be'
Set 'Value field' to 'Z'
Set 'Output Raster Dataset' to '.\Modeling\bin_var6m'
Set 'Cell assignment type' to 'STANDARD_DEVIATION'
Set Cellsize' to '6'                            
Click 'OK'

Find how many points are there:

right click 'lidar_be->Open Attribute Table'

Analyze multiple return lidar data

Add some background data:

Select Menu File -> Add Data -> Add Data...
Select ncshape.mdb/streets_wake
Select ncshape.mdb/lakes
Select ncshape.mdb/streams

Create a Multipoint file from .las point cloud

Turn on the 3D Analyst Extension
Menu -> Customize ->Extensions...
Open the ArcToolbox (if not already open)
Select '3D Analyst->Conversion->From File->LAS to Multipoint'
Set 'Input' to 'tile_0793_016_spm.las'
Set 'Output Feature Class' to '.\Modeling\lidar_mr'
Set 'Average Point Spacing' to '0.5'
Leave the 'Input Class Codes' empty
Set 'Coordinate System' to 'NAD_1983_StatePlane_North_Carolina_FIPS_3200' (you can type 32119 in the search window)
Click 'OK'

Display bare ground and multiple return points over orthophoto:

Select Menu 'File -> Add Data -> Add Data...'
Select ./Modeling/ortho_0793_016_ncspm.tif

Interpolate DSM:

Check out a Geostatistical Analyst Extension license
right click on the empty space next to the Main Toolbar ->Geostatistical Analyst
Select 'Geostatistical Analyst Toolbar->Geostatistical Wizard'
Under 'Deterministic Methods' select 'Radial Basis Function' 
Set 'Source Dataset' to 'lidar_mr'
Set 'Data Field' to 'Z'
Click 'Next'
Under 'General Properties->Kernel Functions' select 'Spline with Tension'
Click 'Finish'
To the Method Report Click 'OK'

Find out where we have multiple returns. First export first return:

Select '3D Analyst->Conversion->From File->LAS to Multipoint'
Set 'Output Feature Class' to '.\Modeling\lidar_r1'
Fill the rest as before but in 'Input return values' check 1

And then second return:

Select '3D Analyst->Conversion->From File->LAS to Multipoint'
Set 'Output Feature Class' to '.\Modeling\lidar_r2'
Fill the rest as before but in 'Input return values' check 2

Overlay with orthophoto. Where do we have second return points?

Optional - display the multiple return data as points in ArcScene

Start ArcScene, add lidar_r1 and lidar_r2 and manipulate with the 3D scene.

FYI: Handling LAS data in ArcGIS

There are three different formats (datasets) that can be used to manage and work with your lidar data in ArcGIS

1. LAS Datasets

To import LAS files into ArcGIS, run the Create LAS Dataset tool in the Data Management toolbox. This will prompt you to load all of your LAS files and create a dataset from them. You can then use the LAS Dataset to Raster tool in the Conversion toolbox to create a raster DEM. See ArcGIS help.

2. Mosaics

You can also import LAS using the Add Rasters to Mosaic Dataset tool. See ArcGIS help.

3. Terrains

The Terrain Wizard in ArcCatalog. Create a feature dataset inside a geodatabase. Import your LAS files using the LAS to Multipoint tool in the 3D Analyst. Save the multipoint feature class in your new feature dataset. Right click on the feature dataset and select New/Terrain to launch the Terrain Wizard. See ArcGIS help here and here.