[GRASS-user] Very high resolution topographic map of Europe: need help and advices: UPDATE

Felix Schalck felix.schalck at gmail.com
Sat Sep 12 17:45:53 EDT 2009


Dear All-who-may-be-intersted,

First, I'd like to apologize for the delay: lots of stuff prevented me
from working on the map. I've got some spared time now, and the map
isn't finished yet - so I'm back into buisiness!
Secondly, I'd like to thank you Markus, for the great script you sent
me: it worked withouth a hitch, and I have now a single big shapefile
to work on. And sorry for the last message: it was a misclick.

Then comes the map: basically, even though the last replies provided
my with some valuable advices, I'm still stuck with bathymetry -
rivers and coastlines.

1. For the bathymetry, I finally took ETOPO1 data, which gives me
another nice raster, although of much lower resolution (1' compared to
the 3" topographic raster from SRTM DEM). So the plan is to cut off
all the land data from the ETOPO1 raster along the coastlines, to keep
only the sea aeras and than paste this reduced raster onto the main
SRTM topographic raster of greater resolution. Can this step be
automated ? (eg: is there a tool to do the job ?) Of course, should
raster-merge be to complicated, there is always the other option,
which is to export pngs first, and paste the pngs together; but in
both cases, the bathymetric raster has to be cut.

2. Rivers and coastlines are a real pain.
a. I could import a big pasted SWBD shapefile thanks to Markus script,
but the cleaning process of the import command takes days, and  gets
somehow stuck within the brigdge removing phase. Result is an
uncomplete vector map, lacking centroids, which can't be further
processed by v.generalize for smoothing (the command dies saying there
is an error in input data), but can be displayed with v.display.
Another problem are all the square borders left around former SWBD
tiles in water aeras; can they be removed ? Or do I have to manually
edit the (huge) vector map ?

b. Then come the rivers: the (somehow corrupted) SWBD vector map shows
only coastlines, smaller closed waterbodies and - although only
partially - larger rivers. I somehow have to complete the river data,
and try following methods:
-r.watershed command in grass, to compute the rivers from DEM data.
This command just dies during the memory allocation process (KILL
signal) because the map is too huge for my system. I tried with
differend -m parameters, but the command always askes for up to 10gb
virtual memory the kernel won't be able to provide. I guess I would
have to work on smaller pieces of the map, set with g.region, and
paste the results together, but this is another time consuming option.
-VMAP0 data import works, but the result is quite disappointing. The
secondary rivers network seems quite good, but this datased is unable
to fix the uncomplete major rivers from the SWBD dataset. For an
instance, by showing both layers (SWBD + VMAP0) on the monitor, I get
all smaller rivers flowing into the rhine, while the rhine itself
remains divided into several un-joined segments.
-OSM(openstreetmap) data is a bit confusing. First it is divided along
countries, so you have to dowload and paste lots of different files.
Than the" Waterway" shapefile is quite poor. And finally the "natural"
shapefile comes with nice river data, but also a lot of confusing
data, like forest aeras. This need some sort of filtering, but I don't
know at all how to do this.

c. Of course, if someone knows better river datasets (scale approching
3", complete, easy to use), I would be happy to try them.

Voila. Even though a lot more problems arise during each step
(resolution has become another one, for an instance), I hope this
project will see an end soon.
Thanks for your help and your patience,

Felix

2009/8/17 Markus Neteler <neteler at osgeo.org>:
> Hi Felix,
>
> On Sun, Aug 16, 2009 at 7:37 PM, Felix Schalck<felix.schalck at gmail.com> wrote:
> ...
>> a - Importing the vectors from SWBD is no problem, tough It would be
>> nice to have the 200+ NASA shapefiles merged BEFORE importing a new
>> layer in GRASS. Is this possible with ogr2ogr ?
>
> Merge of two SHAPE files 'file1.shp' and 'file2.shp' into a new file
> 'file_merged.shp' is performed like this:
>
> # note order "out", then "in":
> ogr2ogr file_merged.shp file1.shp
> ogr2ogr -update -append file_merged.shp file2.shp -nln file_merged file2
>
> The second command is opening file_merged.shp in update mode, and
> trying to find existing layers and append the features being copied.
> The -nln option sets the name of the layer to be copied to.
>
> Attached a script to do as many as you want.
>
>> b - The big problem are coastlines and waterbodies (+main rivers):
>> somehow I have to show them on the topographic map, which gdalwarp has
>> filled out with -32768 values in nodata-waterzones. So either I cut
>> waterbodies out of the topographic raster along the vectors, or I
>> somehow have GRASS compute me all waterbodies from the vector layer,
>> fill them with a nice blue and create a raster which can be pasted
>> over the topographic raster to get the final map.  It seems doable
>> with mapcalc, but frankly, I do not know at all how to proceed. Any
>> help here would be greatly appreciated.
>
> Not sure, but set -32768 to NULL (no data) with r.null?
> Then use r.colors (nv to set color for NULL):
> http://grass.osgeo.org/grass64/manuals/html64_user/r.colors.html
>
> cheers
> Markus
>


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