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#1
How bout DEM dawgs

How bout DEM dawgs

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I can never get my hillshading to look as good as viewed on the National Map's Seamless Sever webpage. The shading always comes out to dark when I run this analysis in ArcMap. I've expiramented some with the azimuth and altitude, but I cant seem to get it right. Any advice/tips/comments on hillshading would be much appreciated. Thanks.

Drew

#2
Hans van der Maarel

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I can never get my hillshading to look as good as viewed on the National Map's Seamless Sever webpage. The shading always comes out to dark when I run this analysis in ArcMap. I've expiramented some with the azimuth and altitude, but I cant seem to get it right. Any advice/tips/comments on hillshading would be much appreciated. Thanks.


If it's too dark, can't you lighten it up a bit? Can you post a sample?
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#3
frax

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I have actually stopped doing it in Arc, and now I always use Photoshop for that - gives me more control.
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#4
Hans van der Maarel

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I have actually stopped doing it in Arc, and now I always use Photoshop for that - gives me more control.


My preferred method right now is rendering 2 types of shading in VNS then compositing them with land-cover data in Photoshop. A bit of a hassle, but great results. I'll see if I can post something here.
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#5
patdunlavey

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I do most of my GIS work in Manifold, so it is logical for me to render the shaded relief there as well. However before I do, I run a transform on the DEM to double or triple the z-values. This provides a greater range of shading values. I usually use a 35 degree sun elevation, and 315 degree azimuth, though you should always test out several variations. I turn off height coloring by setting the height colors all to white. This produces a simple gray-scale relief shade.

It's possible to get a lot fancier. Some techniques I've used at various times:
  • Rendering two shaded relief images with the sun at different azimuths, and selectively combining the two in Photoshop (put one above the other and edit a mask on the top one to selectively reveal the bottom one)
  • Relief bumping:
    • Smooth one copy of the DEM, optionally multiply its z-values by two or three
    • Added the smoothed DEM to the original
  • Elevation contrast - increase contrast at the highest elevations
    • Create a grayscale height mask (low is black, high is white)
    • Use this mask in a levels, curves, or contrast adjustment layer in Photoshop over the original shaded relief
  • Land cover contrast - same idea as above, except use a land cover layer (e.g. alpine) as your mask
  • Slope adjustment to lighten flat areas
    • Create a grayscale image of slope values - flat is white, steep is black
    • Create a curves or levels adjustment layer, using the slope image as a mask, adjust for improvements in value of flat areas

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#6
Kevin McManigal

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Just a thought, but in Arc, I find that I get much better hillshades if I export the DEM as a GRID, and then apply the shade. Then you can use the effects tool to lighten the results more if needed.

Good luck, Kevin
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#7
Lui

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I do most of my GIS work in Manifold, so it is logical for me to render the shaded relief there as well. However before I do, I run a transform on the DEM to double or triple the z-values. This provides a greater range of shading values. I usually use a 35 degree sun elevation, and 315 degree azimuth, though you should always test out several variations. I turn off height coloring by setting the height colors all to white. This produces a simple gray-scale relief shade.

It's possible to get a lot fancier. Some techniques I've used at various times:

  • Rendering two shaded relief images with the sun at different azimuths, and selectively combining the two in Photoshop (put one above the other and edit a mask on the top one to selectively reveal the bottom one)
  • Relief bumping:
    • Smooth one copy of the DEM, optionally multiply its z-values by two or three
    • Added the smoothed DEM to the original
  • Elevation contrast - increase contrast at the highest elevations
    • Create a grayscale height mask (low is black, high is white)
    • Use this mask in a levels, curves, or contrast adjustment layer in Photoshop over the original shaded relief
  • Land cover contrast - same idea as above, except use a land cover layer (e.g. alpine) as your mask
  • Slope adjustment to lighten flat areas
    • Create a grayscale image of slope values - flat is white, steep is black
    • Create a curves or levels adjustment layer, using the slope image as a mask, adjust for improvements in value of flat areas


I'm using the same principle in my hillshading workflow. I'm using custom made Erdas Imagine module where I can set aerial perspective, flat shading, maximum hilshade value, bump mapping,... parameters. The most fun process in hillshading is azimuth generalization. Usually I'm using three (15°-30°) azimuth different hillshade images that are merged together manually in Photoshop.
I was also working on some different hillshading methods. One interesting approach was using some kind of resolution pyramid of DEM. Each pyramid layer was more generalized. This approach allows to set separate parameters of hillshading for each layer so it is possible to create a hillshaded image where more generalized DEM is shaded from main azimuth direction but detailed ones are shaded from different azimuths. The real question was how to generalize DEM and merge together all those shaded images to achive the best result. Using downsampling DEM generalization produced unsharped ridge lines and I have to use geometric generalization of DEM (calculating significant DEM points). For merging I've used normalized bells curve weighted values. Oh one idea came across my mind! This hillshading is really neverending!
A question for Hans: I also tried VNS for hillshade production. I was using several DEM parameters to produce hillshading: elevation, slope, aspect, relative elevation,... even colormap with different color and intensity values. I see a lot of potencial in VNS hillshading but there is one thing that really bother me. Is it possible to shade a large area using light texture (sphere problem) or I have to go with terrain texturing and dissable light(s) compleatly?


Lui

#8
Matthew Hampton

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I can never get my hillshading to look as good as viewed on the National Map's Seamless Sever webpage. The shading always comes out to dark when I run this analysis in ArcMap.


Hi Drew,

The problem you are having has to do with the Z units. They should be the same as the X, Y units. In the NED the X, Y are in decimal degree units and the Z is in meters. With ArcInfo or Arc GIS hillshade there is a Z-factor parameter which can be set to 0.00003 to scale the meters to decimal degrees.

Happy Hillshading! :D

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#9
How bout DEM dawgs

How bout DEM dawgs

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Thanks to everyone for replying. I've found that exporting to a grid is the all important first step (thanks k-map). Good tip with the z-units as well matthew. I'm quite the beginner indeed. However, I suppose if I tinker long enough my ideas will come into fruition. Thanks again for all your help and advice!

Drew

#10
Casey Greene

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I don't know if anyone dropped these yet, but here are two sites that have good information/eye candy for relief-shading:

-ReliefShading.com
-ShadedRelief.com

-Casey Greene
cbgreene17[at]yahoo
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#11
James Hines

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I don't know if anyone dropped these yet, but here are two sites that have good information/eye candy for relief-shading:

-ReliefShading.com
-ShadedRelief.com

-Casey Greene
cbgreene17[at]yahoo

I think one of the members on Carto-Talk is the individual who wrote the first link. Although I will admit that in todays training there isn't too much emphasis on designing the hillshade using vector files such as Photoshop, there's more empasis on just producing one & overlaying a land coverage using different opacities.
"Abbas of novus versus"

#12
MapMedia

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I use ArcMap's Hillshading tool since it has the best hillshading algorithm around IMHO. Around this process, I certainly use the median filter and resample.
Then I use Photoshop, including the Noise>Median filter and controlling the brightness/contrast. I also sometimes add a color overlay of white and adjust its transparency.
Of course don't forget to crop, fade edges as necessary, and resize image before exporting, especially if the hillshade is to be linked in an Illustrator file.
** See the hillshading discussion on Cartotalk re: setting the correct Z factor (super important!!).

Good luck!

#13
ProMapper

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I use ArcMap's Hillshading tool since it has the best hillshading algorithm around IMHO. Around this process, I certainly use the median filter and resample.
Then I use Photoshop, including the Noise>Median filter and controlling the brightness/contrast. I also sometimes add a color overlay of white and adjust its transparency.
Of course don't forget to crop, fade edges as necessary, and resize image before exporting, especially if the hillshade is to be linked in an Illustrator file.
** See the hillshading discussion on Cartotalk re: setting the correct Z factor (super important!!).

Good luck!

I have been using MapRender3D and it gives amazing results. However sometimes to get the correct match of colors one needs hours of trial and error but one can very effectively control each shade based on height data. The depth of shadow can also be controlled. It has one more very robust feature.. a small text file stores the shading parameters and the same can be applied on other data. I do not know if such a feature exists in ArcGIS or Photoshop. With this feature one can generate a hill shading scheme for a coarse dataset; say GTOPO30 and then apply it to the 3 sec or even 1 sec height data in smaller tiles to be merged for a larger picture.

Another very unique feature of this very small software is generating perspective view with accurate hill shading conforming to the height data. I am uploading one sample of a small area with perspective view, it sure looks good.

I sure would like to benefit from any other MR3D user's experiences and also love to know of some workflows to produce similar hill shading by Arc or Photoshop.

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