Sunday, November 22, 2015

Digital Elevation Model (DEM) Resolution Enhancement




03Surface Interpolation


This exercise will guide you through a Method to generate a New finer resolution of a DEM

1. Add the dem grid to ArcMap. Check if the grid has a 30 meter cell size and a UTM projection.

2. Enable Spatial Analyst extension From Customize > Extension.


3. Open ArcToolBox >>  Data Management Tools toolbox / Raster Processing toolset >>Resample.

DEM Resample
DEM  Resample

We now try to resample the 30 meter DEM to finer resolutions. 
First we need to convert the DEM grid into elevation points. 

1. Spatial Analyst Tools toolbox / Extraction toolset >> Sample.

DEM Sampling
DEM Sampling

2. Specify dem 30m as the input raster and as the input location raster, pnt30m_table.dbf as the output, and NEAREST as the resample technique

3. From the ArcMap Layer Panel, right-click on pnt30_table.dbf and select Display XY Data.... Make sure x is in the X field, y in the Y field, and dem30 in the Z field. 


DEM Display
DEM Display points

4. Export the point event data to a shapefile to make them permanent. select Data / Export Data, and save the output as pnt30.shp.

5. Use the spatial interpolation techniques to generate DEMs from the point data set we just created. The first method we use is Inverse Distance Weighted (IDW). 

ArcToolbox/Spatial Analyst Tools/Interpolation.

DEM Interpolation
DEM Interpolation 

6. The DEM automatically added to ArcMap uses a symbology that is difficult to show the subtle variations in the DEM. Change the symbology of the DEM layer from "classified" to "stretched". With this display option, the DEM is displayed as a grayscale map that shows the detail of the terrain.

Converting & Displaying DEM into DTM (Digital Terrain Model)>>
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