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Re: How to plot shaded relief image [message #58020 is a reply to message #57826]

Wed, 09 January 2008 07:49

JMB
Messages: 13
Registered: January 2008

Junior Member

> 1) I have to do this without gridview, because gridview does not
> open it's code.
> 2) I have try the SHADE_SURF with top view, it's good. But I want
> to find a 2D way to do this.

Hi Dave,

Did you already find a "2D" way ?

I tried this method that works pretty good to get a shaded relief from
a digital elevation model (DEM).

- First you need to a create a 3x3 matrix that represents the incident
light with which you want to illuminate your DEM.
- Then you have to convolve your DEM with this matrix. You will get a
kind of shading matrix.
- The last step consists in mixing your colorized DEM with this
shading matrix (which you can to stretch according to get the expected
light/shadows contrast).

; Read the dem into the dem variable (NxM matrix)

dem=read_tiff('dem.tif')

; Edit a 3x3 matrix to represents the light
; in this example the light comes from the bottom (south)

light=[[1,1,1],[0,0,0],[-1,-1,-1]]

; convolution of the dem with the 3x3 matrix

shading=convol(float(dem),float(light))

then you have several ways to use your shading matrix to enhance your
relief plot.
adding or multiplicating the 3 channels of your colored dem with the
stretched shading matrix.

I let you test...

Jérôme

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[Message index]

		Re: How to plot shaded relief image By: David Fanning on Fri, 04 January 2008 07:21
		Re: How to plot shaded relief image By: Dave[4] on Fri, 04 January 2008 07:12
		Re: How to plot shaded relief image By: David Fanning on Fri, 04 January 2008 06:52
		Re: How to plot shaded relief image By: Rick Towler on Fri, 04 January 2008 10:33
		Re: How to plot shaded relief image By: JMB on Wed, 09 January 2008 07:49

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