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


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