[GRASS-dev] SRTM plus color table

[Michael Barton]

So, a little trial and error experimentation produces this: https://www.dropbox.com/s/50s04ur2b86lmo3/srtm_plus_colortable.txt

...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

____________________
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 3:27 PM, Hamish <hamish_b at yahoo.com>
 wrote:

> Michael wrote:
>> GRASS has a lot of nice pre-defined color tables. But one that is
>> lacking is an SRTM-plus color table. This uses the SRTM color table
>> for land, but has enough contrast to also show the sea floor.
>> Currently, only ETOPO2 has a decent color table for the sea floor,
>> but it is so light in shallow water that the land/sea boundary is not
>> easily discernible if combined with the STRM land colors. So here is
>> an attempt to find a combination of SRTM land, plus a pleasing sea
>> floor color table. Maybe someone can improve on it more. In any case,
>> I'd like to suggest that something along this line be incorporated
>> into the stock pre-defined color tables in GRASS.
> [...]
>> ---- SRTM plus color table -----
>> -11000 0:0:0
>> -5000 0:0:70
>> -1000 0:10:130
>> -50 0:70:225
>> 0 0:191:191
> 
> 
> Hi,
> 
> I fully agree that our deep sea colors need some work. The main
> problem with that is if you wish to focus on the continental
> shelves or the deep trenches. Almost all of the ocean floor is
> shallower than 3000m, but there's the occasional dip to 10-11 km.
> Also most of the continental shelf is shallower than 150-200m.
> So a linear color scale doesn't work for all of that range without
> either blurring out the detail in the shelf, or making everything
> below 3km black. IIRC the old etopo and srtm color rules had one
> focusing on the shelf and the other on the deep sea, but both
> could be improved. (when it is just global elevation it seems
> a little odd to name the rules after the datasource, unless the
> rules came directly from them of course)
> 
> Perhaps a numerical approach is to mask off the elevation < 0 in
> one of the global datasets and run 'r.colors -e' to find the nice
> transitions? Probably some tweaks still needed by hand to make
> sure the shelf breaks are still highlighted.
> 
> 
> I would note that this one:
>   http://grassold.osgeo.org/screenshots/images/earthquakes_small2.jpg
> 
> is the same as this,
>   http://grass.fbk.eu/spearfish/earthquakes_small.jpg
> 
> just with the rules bumped to up the contrast, as I find the
> default (observational) Blue Marble 2000 too dark.
> 
> And fwiw these were taken from NOAA's elevation + ice hybrid rules:
>   http://adhoc.osgeo.osuosl.org/grass/earthquakes.png
> but again a supplied R,G,B band image, not mathematical rules.
> 
> 
> summary: a straight linear set of rules are not enough, for
> best results we might need to do a histogram scale for the above
> and below the shelf break, and somehow cleanly transition those
> two together.
> 
> Also finding something which is nice on the computer monitor,
> even when the colors are washed out on a presentation projector,
> and still nice when printed to a page in black and white is
> possible, but not always so easy to do.
> 
> 
> best,
> Hamish