[GRASS-dev] SRTM plus color table

Sun Jan 27 21:27:11 PST 2013

PS: Here's what the color table looks like in an area nearer to you.

https://www.dropbox.com/s/s76xmb7yqz3qgox/Sahul.png

Michael
____________________
C. Michael Barton
Director, Center for Social Dynamics & Complexity 
Professor of Anthropology, School of Human Evolution & Social Change
Arizona State University

voice: 	480-965-6262 (SHESC), 480-727-9746 (CSDC)
fax:          480-965-7671 (SHESC),  480-727-0709 (CSDC)
www: http://www.public.asu.edu/~cmbarton, http://csdc.asu.edu

On Jan 27, 2013, at 10:18 PM, Michael Barton <Michael.Barton at asu.edu>
 wrote:

> I agree with your synopsis. 
> 
> I started with the ETOPO2 ocean colors to see if I could improve them somewhat. 
> 
> I substituted your rule for the one I had for -100. Good on the continental shelf, but it still looked too dark in the deeps. Here is a little more modification. 
> 
> There are various ways of tweaking color tables for particular locales. I'm looking for something of a compromise that works reasonably well for most ocean depths. Probably not really possible, but I thought I'd play around with it some. I think this one is an improvement over what I did earlier.
> 
> -11000 0:0:0
> -8000 0:0:50
> -5000 10:10:100
> -3000 30:30:150
> -1000 70:70:200
> -100 100:100:225
> 0 150:150:255
> 
> Just the ocean part.
> 
> Michael  
> ____________________
> C. Michael Barton
> Director, Center for Social Dynamics & Complexity 
> Professor of Anthropology, School of Human Evolution & Social Change
> Arizona State University
> 
> voice: 	480-965-6262 (SHESC), 480-727-9746 (CSDC)
> fax:          480-965-7671 (SHESC),  480-727-0709 (CSDC)
> www: http://www.public.asu.edu/~cmbarton, http://csdc.asu.edu
> 
> 
> 
> 
> 
> On Jan 27, 2013, at 9:13 PM, Hamish <hamish_b at yahoo.com>
> wrote:
> 
>> Michael wrote:
>>> So, a little trial and error
>>> experimentation produces this:
>> ...
>>> ...with the following color rules.
>>> 
>>> -11000 0:0:0
>>> -8000 0:0:50
>>> -5000 10:10:70
>>> -3000 30:30:100
>>> -1000 70:70:170
>>> -100 100:100:200
>>> 0 150:150:255
>>> 0.1 57:151:105
>>> 100 117:194:93
>>> 200 230:230:128
>>> 500 202:158:75
>>> 1000 214:187:98
>>> 2000 185:154:100
>>> 3000 220:220:220
>>> 5000 250:250:250
>>> 8850 255:255:255
>>> nv 255:255:255
>>> default 255:255:255
>> 
>> I'll respond the long way, with some personal cosmetic
>> observations and critique on ocean colors. YMM(& probably will)V.
>> 
>> my test data is the etopo1 global elevation dataset.
>> See Global Datasets on the grass wiki for links.
>> 
>> r.colors etopo1 color=<>
>> 
>> etopo2 -- ocean colors are not too bad. land colors much too
>> green then harsh transition to white.
>> 
>> 
>> srtm -- only the shallow shelves are visible, most of the ocean
>> is black. Georges Bank off Cape Cod and the North & Baltic Seas
>> show up quite well (often < 100m). ~600m is already black, but
>> for a global view 3000m should still be visible. I find srtm on
>> land to be too brown, but in coastal areas it can look ok, e.g.:
>> http://adhoc.osgeo.osuosl.org/livedvd/docs/_images/grass-fractal.png
>> 
>> 
>> elevation -- relative % based, only intended for land.
>> 
>> 
>> terrain -- a mix of the green from etopo2 with the black oceans
>> of srtm! worst of both worlds? elevation based.
>> 
>> 
>> haxby -- specifically created by W.F. Haxby for highlighting
>> terrain on the sea floor, but for segments of the sea -- not
>> the full range. See also "Digital images of combined oceanic and
>> continental data sets and their use in tectonic studies" in AGU's
>> EOS from a couple months ago:
>> http://onlinelibrary.wiley.com/doi/10.1029/EO064i052p00995/abstract
>> The haxby rules are relative % based scale, so you need to crop
>> out the ocean first:
>> r.mapcalc "etopo1.sea = if(etopo1 <= 0, etopo1, null())"
>> r.mapcalc "etopo1.land = if(etopo1 >= 0, etopo1, null())"
>> 
>> (but even then the scale is too wide, just zoom in on one part
>> of the ocean floor to use them)
>> 
>> 
>> SRTMplus -- the shallow seas have a rather coral-reef look to
>> them, structure of the deep sea seems a bit blurred out.
>> 
>> 
>> proposed (above/dropbox'd): the moonlight effect of the sea
>> floor is nice, although it's a little bit purplish. You can see
>> a bit more structure in the Baltic, and still some structure on
>> Georges Bank and the Hudson Canyon. Around the Bahamas the
>> transitions are a bit harsh.  Like "srtm" I find the land to be
>> too brown for my taste.
>> 
>> 
>> One thing I often do with ocean floor plots is to put the land in
>> greyscale, or as a greyscale shaded relief, with the blue->black
>> ocean. That bypasses any high desert vs. ice cap coloring issues.
>> (shaded relief works best in a non-LL projection)
>> 
>> d.erase 60:60:60
>> r.colors etopo1.sea color=etopo2
>> d.rast -o etopo1.sea
>> d.rast -o etopo1.land.shade    # lowered resolution to 0:05 during creation else it looks to granular
>> 
>> 
>> in summary, etopo2 is my favourite for the deep oceans, but may
>> be too bright if you are strictly looking at the upper 100m of the
>> continental shelves, in that case "srtm" may be better.
>> 
>> adding the following 100m rule to "etopo2" seems to look nice for
>> adding detail in the shallow seas:  (e.g. east coast of the US
>> and the North/Baltic Seas)
>> 
>> -100:100:100:225
>> 
>> (see attached screenshot; but you really need to zoom into a
>> shallow sea like the Bay of Fundy or the Baltic to really see
>> the difference)  It makes the Med look pretty nice too, but that
>> already looked nice with the "etopo2" rules.
>> 
>> I propose to add the above rule to "etopo2".
>> 
>> 
>> regards,
>> Hamish
>> 
>> 
>> -----
>> fwiw,
>> G> r.univar etopo1.sea -e percent=0,10,20,30,40,50,60,70,80,90,100
>> minimum: -10803
>> maximum: 0
>> range: 10803
>> mean: -3433.38
>> standard deviation: 1716.47
>> ...
>> 0th percentile: -10803
>> 10th percentile: -5286
>> 20th percentile: -4902
>> 30th percentile: -4532
>> 40th percentile: -4226
>> 50th percentile: -3890
>> 60th percentile: -3509
>> 70th percentile: -2958
>> 80th percentile: -1863
>> 90th percentile: -253
>> 100th percentile: 0
>> <etopo1_shaded_relief2.jpg>
> 