[Qgis-user] Creating Geological Maps

[Alex Mandel]

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.

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.

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