Spatial interpolation and approximation I: methods
Resources: ESRI virtual campus
Create the assignment working directory (folder) .\Interpolation
Compute DEM based on voronoi polygonsCompute DEM based on voronoi polygons and check it with hillshade.
Compute and display voronoi polygons with centroids (clear data frame).
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 hillshadeFirst create TIN:
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.mdb/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.mdb/terrain/elev_lid792_TERCompute a raster DEM from Terrain,
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 hillshadeInterpolate DEM using IDW:
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'