[Qgis-user] Help on using Transformation Tools plugin

[Andre Joost]

Am 21.01.2013 10:28, schrieb Pietro Rossin:
>
> Hi
> I need some help on using this plugin because It hasn't any howto on its
> usage, or may be I didn't find it.
> I want to use a NTv2 grid for the reprojection between  Monte Mario / Italy
> zone 2 (3004) and Wgs84 (4326).
> My ntv2 is made by two files .asc and .gsb. The .asc is an ascii file and
> inside it I can see
>
> SYSTEM_FROME40 - I think this is the From crs
> SYSTEM_TWGS84  - I think this is the To crs

Well, thats actually not used. The plugin works with the binary version.

>
> So it's intended to reproject from Rome 40 to WGS84, ok.
>
> When I want to setup a new transformation the plugin asks for a
> Transformation name, that is my preferred name, ok.
> System_from should be SYSTEM_FROME40, right?
> What should I use Monte Mario (Rome) 4806 or Monte Mario / Italy zone 2
> (3004)?

If your data is projected (that is in meters), use 3004. 4806 is in degrees.

>
> System_To will be WGS84 (4326).
>
> Then,
> what does it mean with Custom CRSs (CRS A and B name)? Are these only custom
> names used to describe Rome40 and WGS84 in my case?

You don't have to enter anything, the plugin creates a new CRS for you.

> They appear under custom
> Coordinate systems, can I use whatever name I prefer? Then 100000 and 100001
> are custom EPSG automatically generated by TT plugin?
> Then there are two keys on the bottom left part of the plugin window that
> are Apply CRS A ->  B (direct) and Apply CRS A<- B (inverse), the first is
> to reproject from Rome40 to wgs84 an the second the opposite?
>

I have not found any sense in those buttons yet. A bit of documentation 
good be good ;-)

Greetings,
André Joost