[Qgis-user] Creating Geological Maps

[Gerhardus Geldenhuis]

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.


>
> > 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

-- 
Gerhardus Geldenhuis
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