[Qgis-user] Help on using Transformation Tools plugin

[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

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)?

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? 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?

Am I right??

Sorry for the newbie question..

Thank you
Pietro



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