Digital Elevation Model and Shaded Relief 

Introduction

        The purpose for this assignment would like to introduce the user to Digital Elevation Models (DEMs) and some of the three-dimension display capabilities of ER Mapper software. Which, should create in result about a series of shaded relief views for the Halimun Nation Park area of West Java, Indonesia. Should perform complete in the procedure and also answer the question, for this assignment we must take screen grabs such as shaded relief, pseudo color shaded relief and composite shaded relief

Data: Landsat TM and Digital Map

Part One � Create a shaded Relief Display

1. Create a gray �scale shade relief image of the Halimun Nation Park area

a) Open a new pseudo color algorithm window

ง From the ER Mapper window click the New Image Window button, and then click the View algorithm for Image Window button
ง Using the DEM.ers as the data set for add the �Intensity� by click Edit\Add raster layer\intensity from the algorithm window.

Note: Should click on the �GO� button instead the �Auto clip� button because the maximum and minimum values will be cut off

    ง In the transform window we click the Limits button, and then select the actual, if we have the �pseudo� layer present in the current surface we can delete it.

        b) In the Algorithm we click the Edit filter (kernel) for applies a �Low pass� average filter to the DEM.ers in this case we examine conclude with avg3.ker, avg5.ker and avg7.ker

    ง For the Low pass filters we can look at the following directory:C:\ERMAPPER\kernel\filters_lowpass\ ***.ker.

Note: After lode Filter filename in the Filter dialog don�t forgot click the �GO� this step it should help to remove some of the peaks /spikes

        c) Once we have had filtered the DEM in the �Intensity� layer, we can start experimentation with the �Sun Shading� by click Edit Realtime Sunshade option which is available in the Algorithm window.

ง For this process we should experiment with changing the azimuth and elevation options of the sun shade, try azimuth angles of the 45, 270 and 315

Note: This will height light different feature in the image by changing the lighting/Shading effects. However, don�t forget to click on the �Do Sun shading box�, after finish should save our shaded relief image as new algorithm.

        2. Create a �pseudocolor shaded relief� image

    ง Add the pseudo layer to the algorithm
    ง Use the DEM layer as our dataset
    ง Make sure that the limits are set to actual
    ง Select the �Surface� tab in the algorithm window and set both the color mode and the color table to �pseudocolor
    ง Click the �Go� button to see the color shaded relief effect-the blue values represent the lowest elevation values while the red area are the areas of highest elevation

    ง If we open the new algorithm and load DEM.ers, set both the color mode and the color table to �pseudocolor�and the click run we will received result as below

Note: Experiment with using different color tables. Don�t forget to save the favorite �pseudocolor shaded relief�

        3. Create a �composite shaded relief� image

• We can use the same algorithm as before
• Turn off your intensity layer (but don�t delete it!)
• Change the Surface to be RGB by selecting in the RGB color mode from the �Surface� Tab
• Add a �Red� raster layer, �Green� raster layer and a �Blue� raster layer
• Load the �halimun_rectify_48.ers�image into each of the three layers
• Select the composite image combination that we would like to use by specifying the bands from the drop-down lists
• Enhance these bands
• Turn on the intensity layer that holds the shaded relief
• Click the �GO� button
• Save as a new algorithm  

4. Create a Vector overlay with your composition-shaded relief.

ง Add a new vector layout to our composite shaded relief algorithm window

(We should remember how to do this from assignment #1)

ง Load the vector layer (i.e. River or road) by click in Edit button\Add vector layer\Annotation\Map composition

   ง We can select the color chooser button to alter the color that the roads or river will be displayed, and then click on the � GO� button.

Part Two: Create a series of perspective Views

   1. Create an enhanced composition image using the �Halimum_rectify_48.ers�image

   2. Add a �Height� raster layer to the algorithm window. Lode the DEM as the dataset

   3. Add a vector layer to our algorithm layer. The river vector layer is suggested.

   4. Click on the drop down menu beside � View Mode� in the algorithm window and select 3D perspective

Experiment with the different options available in the 3D View (We can change the draw mode) experiment with options available in the algorithm window

5. We could try turning one of your shaded relief images into a 3D perspective view (hint: We would have to add a height layer and should filter the DEM in the height layer)
6. We can move around our image by using the left and right mouse buttons

To rotate the image: hold down the left mouse button and move in any direction. Moving the mouse to the left or right will rotate the image about the Y-axis, moving the mouse up-or down will rotate the image about the X-axis By pushing the left mouse button and then holding down the right mouse button as well, you can rotate the image about Z-axis.

To pan the image (move from side to side): Press and hold the right mouse button and then the left mouse button and relocate the image while continuing to hold the buttons.

To zoom the image: To zoom in, press the right mouse button and drag up the screen. To zoom out, Press the right mouse button and drag down the screen.

Discussion

         The last assignments we had task for performing two pasts, the first one creating a shaded Relief Display that used the halimun_rectify_48.ers and DEM.ers data set for making �Intensity� that we add it from the algorithm after finished we should apply the filter which this assignment we experiment with �low pass� this should help to remove some of the �peaks/spikes� However, please look at in the procedure report for this part we should change azimuth angle and elevation in the �Sun shaded� option compare each of azimuth angle please notice because have question in the Question sheet, so in the past one we learn to used options such a intensity, filter, sun shaded that most of all in the algorithm window. This case we selected the view mode as 2D

             In part two of this assignment, we learn about some of the 3D mode display into the viewer. Because of this viewer mode can show surface trends and topographic feature much more clearly than tradition 2D view mode and when we display the dataset in perspective view mode, we will use the height layer to control the Z-axis (elevation values). 3D perspective view mode we can display the dataset in simply three-dimensional view and helpful adjust the viewpoint to display different perspective view. In the algorithm windows, we add DEM, RGB composite and vector dataset layer to create the three-perspective view. The Tabs in the algorithm windows allow we adjust and control the perspective image.

             In the Layer Tab, we can use to load dataset for each type of layer and define the sun shading for the intensity layer (in case display the shaded 3D perspective image). This tab can also enhance the RGB composite dataset (RGB layers).

             The 3D View Tab allows we use the Lighting to give the light onto the image area. The bounding box can use to define the desired perspective view, the boundary of the view depend on the largest area of all dataset layer. The Resurface button use to clear and re-draw the image view, the Reset View button use to return to the default perspective view, and the Top View button use to draw image in the top view or bird's eye view and also 3D Properties Tab has the function to define the properties of light. The Ambient button use to define the color of the light that can be reflected from the image, it is useful in area where an image receives no direct light.

        Conclusion

            The previous assignment have been required to complete a procedural wrote-up for assignment, for this assignment have two main parts, which conclude; first part were procedure that combination creating and shaded relief display and create a series of perspective views, for second past was the question so, we could perform the procedure and answer the questions. After we completed this assignment we should known method about created a gray-scale shaded relief image that we add the item Intensity layer, could created the filter in the algorithm windows and also compared different when we change name of filter directory, could perform the option of Sun Shading which we should try change for comparing each of azimuth angle, could created a pseudocolor shaded relief image, could also created a composition shaded relief image and in the last one we could created a series of the 3d perspective.

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