HOW TO GENERATE CONTOURS AND HILLSHADE FROM IFSAR DATA

Contours and hillshades are graphic visualization that add details to a geologic map.Here's the process flow for the generation of contours and hillshades for the production of 1:10,000 scale maps using ArcGIS 10.1:

Generating Contours

1. Project

Project the raster image to the projection that you want. In our case, we were given raster data file from NAMRIA with UTM-WGS 51 Northern Hemisphere Projection. We were however, using Luzon 1911 in our maps, hence the need for us to reproject the raster data file.

You can key-in the word "Project" in the search menu and choose "Project Raster (Data Management)" or access the Arctoolbox>Projections and Transformation>Project Raster. Input the necessary data on the fields or drag your loaded raster file on the field, and click OK. A new file shall be generated.

2. Con

We only need to produce contours and hillshades that limits only to 0 elevation and above MSL, i.e, we shall exclude contour data with negative elevations. In order to do this, key in "con" in the search menu or access the arctoolbox to open the Con Dialog box. Drag the reprojected file in the Input Data field. In the condition field, input the following:

"VALUE" > 0

A con file shall be generated.

3. Fill (Spatial Analysis)

In most cases, some areas of the raster contains no data. In order to fill up those spaces, access the "Fill" tool to thoroughly fill out the spaces without data. The "Fill" command shall generate data by taking the average values of its adjacent data. A new "Filled" layer shall be generated.

4. Contour

Now using the generated layer from the "Fill" command, generate contour by typing in contour in the search menu. Use 20 m contour interval. This shall generate 20, 40, and so on contour lines.

5. Contour list

In order to specifically generate contour lines with 4, 8, 12, and 16 m interval, type in "contour list" in the search menu and type in 4 on the list, click the plus (+) button to add the 4m interval, type in 8 and click the plus (+) button and so on.

6. Contour merge

From the operations given above, two layers shall be produced, (1) layer with 20m ci, and (2) layer with 4-8-12-16m ci. In order to combine these two layers into one layer, key in "Merge" in the search menu to open the merge dialog box. Drag the 2 layers on the field option and generate the merged contour layer.

7. Clip

In our project, we were given a 1:10,000 map index. Using the specific map index as border, we clip the produced merged contour in order to erase all the contour lines that are outside the map index.

Generating Hillshade

1. Key-in "Hillshade" in the search menu to open the Hillshade dialog box. Drag the raster file produced from "Fill" to produce the hillshade. 

2. Clip the produced raster hillshade using the map index as border.

Map with contours

Map with hillshade