NCSU GIS/MEA582:
Geospatial Modeling and Analysis

Spatial interpolation and approximation I: methods

Resources: ESRI virtual campus

Create the assignment working directory (folder) .\Interpolation

Start ArcMap

Compute DEM based on voronoi polygons

ArcMap File->Add Data->Add Data...
Select ncshape.mdb/elev_lid792_randpts
Open the ArcToolbox
Select 'Analysis Tools->Proximity->Create Thiessen Polygons' 
Set 'Input Features' to 'elev_lid792_randpts'
Set 'Output Feature Class' to '.\Interpolation\elev_vor.shp'
Set 'Output Fields' to 'ALL'    
Click 'OK'
NOTE: this process may take a while...
Select 'Data Management Tools->Features->Feature to Point'
Set 'Input Features' to 'elev_vor'
Set 'Output Feature Class' to '.\Interpolation\vor_center.shp'
Leave the 'Inside' box unchecked
Click 'OK'

Convert to raster and display with standard elevation color.

Open the ArcToolbox (if it's not already open)
Select 'Conversion Tools->To Raster->Polygon To Raster'
Set 'Input Feature' to 'elev_vor'
Set 'Value Field' to 'value_'
Set 'Output Raster Dataset' to '.\Interpolation\elev_vor2m'
Set 'Cellsize' to '2'         
Click 'OK'

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

Select Menu Geoprocessing->Environments...->Raster Analyst
NOTE: this will set the default cell size to 2 units (meters) for all subsequent processing.
Set Cell Size to 'As Specified Below'
Set the cell value to 2
Click 'OK'

Check the result using hillshade.

Check out a 3-D Analyst Extension license
Open the ArcToolbox (if it's not already open)
Select '3D Analyst->Raster Surface->Hillshade'
Set 'Input Surface' to 'elev_vor2m'
Set 'Output Raster' to '.\Interpolation\Hillsh_vor_2m'
Click 'OK'

Interpolate DEM using TIN and check it in ArcScene or hillshade

Select 3D Analyst Tools->Data Management->TIN->Create TIN
Set 'Output TIN' to '.\Interpolation\elev_lid792_TIN'
Set Input Feature Class to 'elev_lid792_randpts'
In the tablem change the entry in the  'height_field' column to 'value_'
and 'SF_type' to 'Mass_Points'
Click 'OK'

Interpolate TIN to raster DEM.

Open the ArcToolbox (if it's not already open)
Select '3D Analyst Tools->Conversion->From TIN->TIN to Raster'
Set 'Input Tin' to 'elev_lid792_TIN'
Change the 'Sampling Distance' to CELLSIZE 2 (Note: you will have erase the previous value and type 2)
Set Output Raster to .\Interpolation\tinrast_2m
Leave all else as default
Click OK

Display as hillshade:

Open the ArcToolbox (if it's not already open)
Select 3D Analyst Tools->Raster Surface->Hillshade'
Set 'Input Surface' to 'tinrast_2m'
Set 'Output Raster' to '.\Interpolation\Hlshtinrast2m'
Click 'OK'

Create the Terrain Model using the Terrain Wizard in ArcCatalog.

Create a new empty file geodatabase and feature dataset.

right mouse click on the Interpolation folder in ArcCatalog
Choose New->File geodatabase
Set the geodatabase name to 'Interpolation_terrain'

Create a new feature dataset called 'terrain' in the new 'Interpolation_terrain' geodatabase.

right mouse click on the 'Interpolation_terrain' geodatabase and select New->Feature dataset
Set name to 'terrain'
click 'Next'

Set (Import) the horizontal coordinate system for the dataset to that associated with the vector point feature class 'elev_lid792_randpts'.

Click on the globe with star icon (next to the search window) -> Import
Inticate the path ./ncshape.gdb/elev_lid792_randpts
Finish with defaults

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

In the ArcCatalog,
Drag the elev_lid792_randpts into the created feature dataset
(or use right click to Copy and Paste)
Click 'OK' in the pop up window

Construct the Terrain Model:

In ArcCatalog right mouse click on the 'terrain' feature data set, select NEW->Terrain

In the Terrain Wizard:

Set the terrain name to 'elev_lid792_TER'
Set the participating feature class to 'elev_lid792_randpts'
Set the Approximate point spacing to 1m (average distance between points)
Click 'Next'
Set the Height Source to 'value_' (Note: this is a drop-down menu)
Click 'Next'
For Select pyramid type, choose defaults
Click 'Next'
Click 'Calculate pyramid properties' to generate two 2 pyramid levels
Click 'Next'
Review the displayed summary
Click 'Next'
Click 'Finish' to build new terrain
Click 'Yes' in the pop up window to build the created terrain

Add the terrain to your ArcMap project

ArcMap File->Add Data->Add Data...
Select ./Interpolation/Interpolation_terrain.gdb/terrain/elev_lid792_TER

Open the ArcToolbox (if it's not already open)
Select '3D Analyst Tools->Conversion->From Terrain->Terrain to Raster'
Set 'Input Terrain' to 'elev_lid792_TER'
Change the 'Sampling Distance' to CELLSIZE 2 (Note: to will have to erase the previous value and type 2)
Set Output Raster to .\Interpolation\terrast_2m
Leave all else as default
Click OK

Interpolate DEM using IDW and check it with hillshade

Open the ArcToolbox (if it's not already open)
Check out a Spatial Analyst Extension license
Select 'Spatial Analyst Tools->Interpolation->IDW'
Set 'Input point features' to 'elev_lid792_randpts'
Set 'Z value field' to 'value_'
Set 'Output Raster' to '.\Interpolation\elev_idw_2m'
Leave the other inputs as defaults
Click 'OK'

Check the interpolated elevation surface using hillshade:

Open the ArcToolbox (if it's not already open)
Select '3D Analyst Tools->Raster Surface->Hillshade'
Set 'Input raster' to 'elev_idw_2m'
Set 'Output Raster' to '.\Interpolation\Hillsh_idw_2m'