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DEM to Shaded Relief Anguish

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#1
Chris G

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Hello,

I've been working on this for week, as I am very new to using the tool of the GIS/Cartography trade. I'm hoping to create a recreational map (1:20,000 approx) of a canoe route along the Moon River in Ontario, and would like to make use of shaded relief to give the map that extra bit of styling.

I have a 10 meter DEM that I've downloaded from GeoBase (Canada), which look something like this:
http://www.chrisgars...m/stuff/DEM.png

I then resample it to a much higher resolution, something like this:
http://www.chrisgars...M_resampled.png

Then I try the shaded relief:
http://www.chrisgars.../DEM_shaded.png

I'm a little confused when the shaded relief is so coarse, when the inital DEM was resampled to such a high resolution. I've been playing with all kinds of settings in GRASS and ArcMap to try and get this to appear better, but to no avail.

Should I now be taking this into a paint program to clean up? Is there a break in my process that is preventing the shading from being smoother?

Ideally, I'd like to drape some vector contours over this to really make it look slick. A good example of what I'm trying to do can be found here:

http://www.mindbird.com/2f770f2f0.jpg

You will have to excuse my newness. I have looked around at many website discussing this topic, but there's a very wide range of potential solutions, and many of them are dealing with small scale maps.

Thanks for any help,
Regards,
Chris

#2
Hans van der Maarel

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I'm a little confused when the shaded relief is so coarse, when the inital DEM was resampled to such a high resolution. I've been playing with all kinds of settings in GRASS and ArcMap to try and get this to appear better, but to no avail.

Should I now be taking this into a paint program to clean up? Is there a break in my process that is preventing the shading from being smoother?


Resampling isn't going to help you much I'm afraid. Your output shaded relief resolution is largely dependant on your input DEM resolution. What's your intended output resolution?

Are there any options in [whatever app you're using to do the shaded relief] to do any smoothing? I know VNS 3 does phong shading which makes the results of a coarse DEM look somewhat better. Alternatively, you could play with it in Photoshop afterwards.
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#3
meghan m

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I had the same problem, and in the end I had to Photoshop the whole thing. Use the blur tool in small patches to test it out because it might take out the bright colours, and the use the smudge tool. It is your friend.

#4
rudy

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I'm a little confused when the shaded relief is so coarse, when the inital DEM was resampled to such a high resolution. I've been playing with all kinds of settings in GRASS and ArcMap to try and get this to appear better, but to no avail.

Should I now be taking this into a paint program to clean up? Is there a break in my process that is preventing the shading from being smoother?


Resampling isn't going to help you much I'm afraid. Your output shaded relief resolution is largely dependant on your input DEM resolution. What's your intended output resolution?

Are there any options in [whatever app you're using to do the shaded relief] to do any smoothing? I know VNS 3 does phong shading which makes the results of a coarse DEM look somewhat better. Alternatively, you could play with it in Photoshop afterwards.


Your best bet is to get a higher resolution DEM . . . you can't resample it to a higher resolution to make it better. Geobase has both 1:50,000 and 1:250,000 scale DEMs. If you are looking for something better you might need to look by province. Ontario, for example, has 1:10,000 and 1:20,000 DEMs but I'm not sure if they are readily available online or if the are free.

#5
Justin

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I had this issue because the TIFF was 8-bit and looked grainy and coarse, have you attempted to convert the image to 16-bit to see if it comes out better?

You may also see if there are any higher meter-resolution sources for the area you're working on.

The blur tool in Photoshop helps, along with the lighting effects filter if you have access to that.

#6
Chris G

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I had this issue because the TIFF was 8-bit and looked grainy and coarse, have you attempted to convert the image to 16-bit to see if it comes out better?

You may also see if there are any higher meter-resolution sources for the area you're working on.

The blur tool in Photoshop helps, along with the lighting effects filter if you have access to that.


Hmmm, I've converted the DEM from DEM to raster, making it floating point, instead of integer. My thought was the by making it floating point, and then resampling, it would smooth the terrcing effect out. I guess I had assumed that the terracing might be caused because the DEM was signed integer, so there was no decimal values.

I'll check the bit depth, but I think it's already 16 bit, so I'm not sure this will sort it out.

Is the only way to do a 1:20000 shaded relief map to try and find DEMs of a higher resolution than 10m? I suspect if these exist, they won't be freely availble, since generating a DEM of less than 10m using remote sensing would be an expensive process.

Is there perhaps a way to create a much smoother surface by generating the shaded relief raster from a counter data set? I'm exporing this in GRASS and ArcMAP at the moment, but soon have to head off to work! Always in the way!

Thanks again for everyones input, it's been very helpful.

Regards
Chris

#7
Charles Syrett

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Since your stated purpose for shaded relief on this map is to add "an extra bit of styling", I think it's way overkill to look for hi-res DEMs or spend a lot of time getting really technical. Just use what you have as a starting point. Create a basic image that you can fit to your other map detail, and then use Photoshop or any other raster editing program to smooth out the image. My favourite tools are Gaussian blur and Noise>Median. Usually an artful combo of these will kill the terracing. If you need to work some sharpness and detail back in, use the airbrush tool, with contours and drainage as a guide. I think you may find this approach to be far faster, more effective, and more fun, than trying to find an analytical solution. B)

Charles Syrett
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http://www.mapgraphics.com

I had this issue because the TIFF was 8-bit and looked grainy and coarse, have you attempted to convert the image to 16-bit to see if it comes out better?

You may also see if there are any higher meter-resolution sources for the area you're working on.

The blur tool in Photoshop helps, along with the lighting effects filter if you have access to that.


Hmmm, I've converted the DEM from DEM to raster, making it floating point, instead of integer. My thought was the by making it floating point, and then resampling, it would smooth the terrcing effect out. I guess I had assumed that the terracing might be caused because the DEM was signed integer, so there was no decimal values.

I'll check the bit depth, but I think it's already 16 bit, so I'm not sure this will sort it out.

Is the only way to do a 1:20000 shaded relief map to try and find DEMs of a higher resolution than 10m? I suspect if these exist, they won't be freely availble, since generating a DEM of less than 10m using remote sensing would be an expensive process.

Is there perhaps a way to create a much smoother surface by generating the shaded relief raster from a counter data set? I'm exporing this in GRASS and ArcMAP at the moment, but soon have to head off to work! Always in the way!

Thanks again for everyones input, it's been very helpful.

Regards
Chris






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