Hi,
Start with finding a background map or a project CRS that is similar to
your old maps. That takes a bit of guessing. Then select the Helmert
method in the transformation method. All you need is 2 GCP (ground
control points). If you add more, you will see how you map is warped and
how points drift. Once you are happy with the results, then change the
method to Thin Plate Spline and you can start adding GCP and testing the
results. That will and can really warp the map so be careful with this
method.
Nicolas
On 2021-08-25 1:26 p.m., Firstname Lastname wrote:
hello
i am trying to do some basic georeferencing. i have been using the
georeferencing tool and i have been following the workflow suggested
on youtube files using the georeferencing tool
i have tried three different maps of new and old vintage. i have tried
to keep it simple with 4 points control points and have used as many
as 10 points. when i apply the georeferencing, my maps are not
calibrating. even the control points end up 400-600 m. of off the
true coordinates. Any suggestions that might help fix this.
for reference, i used the epsg 3857 CRS
--
Byron Veilleux, MSc. P.Geo
Conjugate Geologic Services Limited
Calgary, Alberta Canada
by...@conjugategeo.com <mailto:by...@conjugategeo.com>
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--
Nicolas Cadieux
https://gitlab.com/njacadieux
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