[Proj] Pipeline +init files, inverse

[Thomas Knudsen]

use
    +init=blabla +inv

For cct, there's also the -I switch:

    cct -I +init=blabla

/Thomas

2018-02-21 22:18 GMT+01:00 stevejking <stevejking at talktalk.net>:

> Is it possible to use a +init pipeline file in reverse?
>
> For example, with some explanation from Kristian, I now have two
> transformations:
>
> # OSGB1936 to ETRS89(2)
> <7709-3D>                  -t0 +proj=pipeline \
>                       +step +proj=tmerc +lat_0=49 +lon_0=-2 +k=0.9996012717
> +x_0=400000 +y_0=-100000 +ellps=airy +inv \
>                       +step +proj=vgridshift
> +grids=OSGM15_GTX_OSGBtoGRS80.gtx +inv \
>                       +step +proj=hgridshift
> +grids=OSTN15_NTv2_OSGBtoETRS.gsb
>
> # ETRS89 to OSGB1936
> <7709-3D-Reverse>     -t0 +proj=pipeline \
>                       +step +proj=hgridshift
> +grids=OSTN15_NTv2_OSGBtoETRS.gsb +inv \
>                       +step +proj=vgridshift
> +grids=OSGM15_GTX_OSGBtoGRS80.gtx \
>                       +step +proj=tmerc +lat_0=49 +lon_0=-2 +k=0.9996012717
> +x_0=400000 +y_0=-100000 +ellps=airy
>
>
> The only difference between the two is the reverse order and swapping the
> +inv and 'no inv blanks' on the end of each line. I'm wondering if I need
> two separate transformations?
>
> If not is it a sensible future development? +init=<...> +reverse ?
>
> Steve
>
>
>
> --
> Sent from: http://osgeo-org.1560.x6.nabble.com/PROJ-4-f3840930.html
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