[GRASS-dev] i.ortho.photo/lib/ref_points.c and making a REF_POINTS file

Markus Metz markus.metz.giswork at gmail.com
Mon May 8 23:45:31 PDT 2017

Hi Yann,

On Mon, May 8, 2017 at 10:12 PM, Yann <dr.yann.chemin at gmail.com> wrote:
> Hi,
> Looking for some lore from i.ortho.photo days in GRASS 6 and before...
> Within i.image.2target, i.ortho.transform requires a REF_POINTS (image E,
image N, photo X, photo Y) file as part of its RMS error computation,
before using a CONTROL_POINTS (photo X, photo Y, photo Z, control X,
control Y, control Z) file made by i.image.2target interactive GCP creation
> the i.photo.2image module, to my understanding is from (photo X, photo Y)
to (image X, image Y), i.e. we keep in the non-map units, we only find the
proper coordinates of the camera within the camera absolute dimensions
(i.e. mm or other). So I do not believe it is related to generating a

the i.photo.2image module does generate a REF_POINTS file. This is needed
to translate from sensor (mm) to image (xy, pixels) and back. The sensor is
e.g. the CCD in a DSLR, e.g. for Canon EOS-1Ds the sensor would be 35.8 mm
× 23.8 mm.


Markus M
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