[Qgis-user] Primitive Troubleshooting

[Stephen Wandling]

Earlier I was trying to figure out why Composer wanted to export raster 
files, and I wanted vector.  I finally reduced my 'map' to the raster 
base map and one local shape file, Roads.  With this I found that 
selecting the layer Roads and using "Set Project CRS to this Layer" was 
causing Composer to default to raster output.  A clue!

I had noticed that the raster base map rotated 2 or 3 degrees CW when I 
used "Set Project CRS to this Layer", above.  I also noticed that in 
Composer, if I had not used "Set Project CRS to this Layer", placing a 
UTM grid on my map resulted in the grid being rotated 2 or 3 degrees 
CCW.  So, it appears that the grid is based on the base map?

In reading today's posts, I noted mention of Georeferencer.  Digging 
into this, the tutorials, etc seemed to require having another input, to 
compare points.  I thought I might be able to accomplish this by 
comparing my Roads layer with the raster map.

I loaded my local Roads shape file into a new canvass in QGIS and my 
raster base map into Georeferencer.  I would click a particular 
intersection in georeferencer and it would produce the 'enter 
coordinates' or 'get from map' options.  Selecting the latter, it 
switched to the map canvass and I could zoom in and click the same 
intersection.  This would send me back to the previous menu where the 
coordinates were filled in and I would select OK.  I did this on 4 
points.  On the fourth point, I noted the red line angled 2 or 3 degrees 
CW, but quite long.

I saved the points in a file and Started Georeferencing.  The completed 
raster base map came up on the QGIS canvass, along with the Roads shape 
file.

What I saw did not please me.  In some places, the Roads were now 
falling at least 1/2 kilometer off from the base map road locations.  
This put them in creek ravines and other hillshade elements.  The 
results were unusable for my purposes.

When I had used "Set Project CRS to this Layer", the Roads layer fell 
onto the roads on the raster map.  Streams fell onto their ravines.

Maybe I have to get another base map?  Or maybe my georeferencing method 
was faulty?

Stephen