NCSU GIS/MEA582:
Geospatial Modeling and Analysis

Spatial interpolation and approximation I: methods

Resources: ESRI Academy

Launch ArcGIS Pro and login with ArcGIS Online credentials if required. Select New> Map> Create New Project. Create a new project in your preferred workspace, in the instructions below we are using the default C:\Users\myname\Documents\ArcGIS\Projects\ folder.

Use your judgement to decide which maps to include in your report.

Compute DEM based on voronoi polygons

On the Map tab, in the Layer group, click 'Add Data'
Browse to C:\Users\myname\Documents\ArcGIS\582data\ncshape.gdb
select 'elev_lid792_randpts'
'OK'

In the Geoprocessing pane, search for and select the 'Create Thiessen Polygons' tool
Set 'Input Features' to 'elev_lid792_randpts'
Set 'Output Feature Class' to 'elev_vor.shp'
Set 'Output Fields' to 'All fields'    
Click 'Run'
In the Geoprocessing pane, search for and select the 'Feature to Point' tool
Set 'Input Features' to 'elev_vor'
Set 'Output Feature Class' to 'vor_center.shp'
Leave the 'Inside' box unchecked
Click 'Run'

Convert to raster and display with standard elevation color.

In the Geoprocessing pane, search for and select the 'Polygon To Raster' tool
Set 'Input Feature' to 'elev_vor'
Set 'Value Field' to 'value_'
Set 'Output Raster Dataset' to 'elev_vor2m'
Set 'Cellsize' to '2'         
Click 'Run'

Set the Raster Analyst Cell Size to 2m in Environment Settings.

On the top ribbon->'Analysis' tab->'Geoprocessing' group->'Environments'->'Raster Analysis' section
NOTE: this will set the default cell size to 2 units (meters) for all subsequent processing.
Set 'Cell Size' to a value of 2 by typing in the box
Click 'OK'

Check the result using hillshade.

In the Geoprocessing pane, search for and select the 'Hillshade' tool
Set 'Input Raster' to 'elev_vor2m'
Set 'Output Raster' to 'Hillsh_vor_2m'
Click 'Run'

Interpolate DEM using TIN and check it in a Scene or with hillshade

In the Geoprocessing pane, search for and select the 'Create TIN' tool
Set 'Output TIN' to 'elev_lid792_TIN'
Set Input Feature Class to 'elev_lid792_randpts'
Set the 'height field' to 'value_'
Set 'Type' to 'Mass_Points'
Click 'Run'

Interpolate TIN to raster DEM.

In the Geoprocessing pane, search for and select the 'TIN to Raster' tool
Set 'Input Tin' to 'elev_lid792_TIN'
Set Output Raster to tinrast_2m
Change the 'Sampling Distance' to 'CELLSIZE' and sampling value to '2'
Leave all else as default
Click 'Run'

Display as hillshade:

In the Geoprocessing pane, search for and select the 'Hillshade' tool
Set 'Input Raster' to 'tinrast_2m'
Set 'Output Raster' to 'Hlshtinrast2m'
Click 'Run'

Create the Terrain Model using the Terrain Wizard

A terrain dataset is a multiresolution, TIN-based surface built from lidar/sonar/photogrammetric measurements stored as features in a geodatabase.

Create a new feature dataset called 'terrain' in the your assignment 3 geodatabase.

In the Geoprocessing pane, search for and select the 'Create Feature Dataset' tool
Set 'Output geodatabase' to the project geodatabase
Set 'feature dataset name' to 'terrain'
Set 'coordinate system' to match elev_lid792_randpts
click "Run"

Add the feature class data that will be used to create the terrain

In the Geoprocessing pane, search for and select the 'Feature class to feature class' tool
Set 'input features' to 'elev_lid792_randpts'
Set 'output location' to 'terrain'
Set 'output feature class' to 'elev_lid792_rand_fc'
Click 'Run'

Run the Create Terrain tool

In the Geoprocessing pane, search for and select the 'Create Terrain' tool
Set 'Input feature dataset' to 'terrain'
Set 'Output Terrain' to 'elev_lid792_TER'
Set the 'Average point spacing' to '1' (average distance between points)
Set 'Pyramid type' to 'Z tolerance'
Click 'Run'

In the Geoprocessing pane, search for and select the 'Add terrain pyramid level' tool
Set 'Input terrain' to 'elev_lid792_TER'
For 'Pyramid levels definition' type each of the following on a new line:
1 5000
2.5 10000
5 25000
10 50000
Click 'Run'

Using the settings above, the full-resolution data is used in map displays up to a scale of 1:5,000, Between 1:5,000 and 1:10,000, only the data necessary to achieve an approximate vertical tolerance of 2.5, relative to the full-resolution data, is used. Between 1:10,000 and 1:25,000, a tolerance of 5 is used. For any scale smaller, a tolerance of 10 is used to display the terrain data.

Add the feature class to the terrain

In the Geoprocessing pane, search for and select the 'Add Feature class to terrain' tool
Set 'input terrain' to 'elev_lid792_TER'
Set 'input features' to ''elev_lid792_rand_fc'
Set 'height field' to 'value_'
Click "Run"

Build terrain

In the Geoprocessing pane, search for and select the 'Build terrain' tool
Set 'input terrain' to 'elev_lid792_TER'
Click "Run"

In the Geoprocessing pane, search for and select the 'Terrain to Raster' tool
Set 'Input Terrain' to 'elev_lid792_TER'
Set Output Raster 'terrast_2m'
Change the 'Sampling Distance' to 'CELLSIZE' and value to '2' 
Leave all else as default
Click 'Run'

Interpolate DEM using IDW and check it with hillshade

In the Geoprocessing pane, search for and select the 'IDW' tool
Set 'Input point features' to 'elev_lid792_randpts'
Set 'Z value field' to 'value_'
Set 'Output Raster' to 'elev_idw_2m'
Leave the other inputs as defaults
Click 'Run'

Check the interpolated elevation surface using hillshade:

In the Geoprocessing pane, search for and select the 'Hillshade' tool
Set 'Input raster' to 'elev_idw_2m'
Set 'Output Raster' to 'Hillsh_idw_2m'