[Qgis-user] Creating Geological Maps

[Alister Hood]

> Date: Sun, 16 Oct 2011 15:29:42 -0700
> From: Alex Mandel <tech_dev at wildintellect.com>
> Subject: Re: [Qgis-user] Creating Geological Maps
> To: Qgis-user at lists.osgeo.org
> Message-ID: <4E9B5AD6.3030706 at wildintellect.com>
> Content-Type: text/plain; charset=ISO-8859-1
> 
> On 10/16/2011 02:26 PM, Gerhardus Geldenhuis wrote:
> > On Sun, Oct 16, 2011 at 10:03 PM, Alex Mandel
> <tech_dev at wildintellect.com>wrote:
> >
> >> On 10/16/2011 01:32 PM, Gerhardus Geldenhuis wrote:
> >> Just to check, do you have projection on-the-fly turned on? For
best
> >> image quality the image needs to be in it's native projection.
Though in
> >> this case it sounds like you just opened the image file to look at
it.
> >> How does it look in something like GIMP when you zoom in?
> >>
> >
> > Hi Alex
> > Many thanks for the reply!
> >
> > No idea if I have project on-the-fly turned on, I could not see any
> > reference to it in the project properties or options.
> > Native projection? I scanned the paper images and the scanner saved
them as
> > jpeg files. I then opened up the images in The Gimp rotated and
aligned the
> > to a drawing grid in Gimp because they were about 1 degree skewed. I
> > had pencilled lines on the paper that represented UTM grid lines. I
saved
> > these as both jpg and png format both in lowest compression thus
highest
> > quality. Viewing either the jpg or png file in Gimp or Image Viewer
is fine
> > and if I zoom in to 1:1 scale the quality is perfect.
> >
> >
> Redo that, and try to get a tiff or png from your scanner. Also there
is
> no need to manually rotate the image as georeferencing will take care
of
> that. The fewer saves/conversion along the process the better.

Feel free to try scanning as tiff, but since the image you already have
displays clearly at 100% or in other image viewers, I doubt that will
solve the problem.
I think the problem is that the gdal provider in QGIS (this is what is
used to load raster image files) does not do antialiasing ("smoothing").
Raster antialiasing is particularly important for scanned maps.  I
thought there was an enhancement ticket for it, but I can't find it.
Does anybody else know?  Perhaps it was just discussed on one of the
lists.

> You probably do not have on-the-fly on since it's off by default.
> >>
> >>> Second question is how can I "align" this png file with with an
actual
> >>> co-ordinate system. I have marked 4 points on my paper maps and
lines
> >>> between these points that represent the UTM grid on which I worked
and I
> >>> would need to at least roughly align this image with the UTM grid.
> >>>
> >>
> >> Georeferencing plugin, this will turn your tiff into a GeoTiff, the
same
> >> as what you might get from preprocessed ASTER data. You can mark
and
> >> enter known coordinate locations and then warp the image to fit.
> >>
> >
> > That sounds excellent I am going to try that now.
> >
> >
> >>
> >>> Thirdly I am not sure how to draw on a new layer but still view my
image
> >> as
> >>> a template for the digitizing.
> >>>
> >>> I am more than happy to read any documentation and work through
> >> tutorials.
> >>> What is lacking at the moment is the terminology to search for the
> >> correct
> >>> things and experience. I am working through a number of tutorials
but are
> >>> still struggling a bit to connect A to B.
> >>>
> >> Read the manual on the QGIS website, create a new vector layer and
> >> editing it can be over anything else you have loaded in the map
view.
> >> http://qgis.org/en/documentation/manuals.html
> >>
> >>> I will eventually add some ASTER imagery but it is my
understanding that
> >>> these are in tiff format and contains extra information like
spatial
> >>> referencing. I suspect that if I can master the above then adding
ASTER
> >>> imagery will be easy.
> >>>
> >>> Lastly is there any geological map symbol databases available?
> >>>
> >> It's been discussed and some work has been done on it but nothing
> >> comprehensive yet. If you have Images or Fonts of the symbols you
want
> >> you can easily convert them for use in QGIS.
> >>
> >>
> > A shame, I have send of an email to the British Geological Survey
and see
> > what they come back with. I might have access to the ArcGIS and
could load
> > the images database provided by the US Geological Survey. Not sure
if ArcGIS
> > would allow me to export it into something more usable. My google
results
> > turned up an email thread which suggested that there was some work
done on
> > supporting gdb files...
> >
> > Regards
> >
> ESRI icons are all fonts, and can be converted using fontforge to svg.
> Though I don't know anything about the licensing.

You can use font symbols in QGIS, and the ESRI fonts are probably
installed with their free viewers... using them could well violate the
license though ;)

> We are trying to work on more open sets, a preliminary list of things
> that might help is here:
> http://wiki.osgeo.org/wiki/OSGeo_map_symbol_set
> 
> The USGS symbols are available but need to be cut on and converted
using
> GIMP/Inkscape if you want scalable svg.
> 
> Thanks,
> Alex

Alister