[Qgis-user] Aligning georeferenced USGS historical maps

[Morgan Fletcher]

I am new to GIS, an amateur who is curious about old roads. I have QGIS
3.4.0 installed on OS-X 10.13.6 using the pre-built binaries available from
https://download.qgis.org/. If I visit the USGS topoView
<https://ngmdb.usgs.gov/topoview/> page and download a historic map, for
instance the geotiff archive from Tamalpais, CA 1897 (1950 ed.)
<https://ngmdb.usgs.gov/topoview/viewer/#10/37.8564/-122.6336>, I can add a
raster layer with the .tif file from the archive and it will be placed in
rough correspondence with a base map in my QGIS project. In my case my
basemap is OpenStreetMap. (crs=EPSG:3857&format&type=xyz&url=
http://a.tile.openstreetmap.org/%7Bz%7D/%7Bx%7D/%7By%7D.png&zmax=19&zmin=0)
The problem is that the maps don't line up, visually. For example:


 Screen Shot 2018-11-02 at 8.51.02 AM.png
<https://drive.google.com/a/hahaha.org/file/d/0B-OybZpGWIkHUWhuWEZLS2xWZEhTUC1MMkN4X2dfZGkxQm1J/view?usp=drive_web>


I can solve it better with georeferencer. Before I viewed Hans van der
Kwast's excellent Georeferencing a scanned map and digitizing vectors in
QGIS <https://youtu.be/4IWyVeGhzog> video, I simply started finding common
points; now I understand that using the correct CRS, projection and the
grid is perhaps perhaps the best strategy.

My questions are:


   - If I download a geotiff archive from topoView, is QGIS 3.4.0 correctly
   parsing the data in the .tif file, or the other files (.prj, .tfw) in the
   extracted directory, and placing the map correctly? Can it be adjusted to
   align better, and if so, how?
   - Should I use EPSG:26710 for the Tamalpais
   <https://ngmdb.usgs.gov/topoview/viewer/#10/37.8754/-122.6260> map, and
   attempt to georeference it myself, using its minute grid? Why does the map
   border show a skew at the top left and right corners? (see below)
   - I have found that, to get a hand-drawn, antique map to align with a
   modern base map, I often have to add so many points in georeferencer that
   the rendered map has to be very distorted. What is the best method to get
   old maps to line up, so that historical roads can be related to modern
   roads?

Skew mentioned in second point:


 Screen Shot 2018-11-08 at 8.20.56 AM.png
<https://drive.google.com/a/hahaha.org/file/d/0B-OybZpGWIkHeEE0aDMyQVFCZ0F1R01pRGhKeEJVTzYxaEpj/view?usp=drive_web>


I couldn't find a searchable archive of qgis-user; my apologies if these
are already answered somewhere. I did ask a variation of these questions on
StackExchange
<https://gis.stackexchange.com/questions/301199/fix-offset-of-geotiff-file>,
where it was heavily edited by 'Vince', and has no answers after a week, so
asking here.

Morgan
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