Overriding existing CRS

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Overriding existing CRS

"Peter Mozolík (Gmail)"
Hello,

I'm new to uDig. I have few questions.

1. Is it possible to override internal definition of existing CRS (e.g I
want to modify TOWGS parameter). I have found file "epsg.properties" in
directory <UDIG>/plugins/net.refractions.udig.libs_<version>. I guess
its purpose is to add new CRS into uDig, but I'm not sure about uDig
behaviour if I use same code (and eventually name) as already defined CRS.

2. Could you please exaplain how internal db of CRS definitions is
built, I mean if there is some automatic process to build internal db
from official epsg registry. How often is internal database of CRS updated?

3. Does uDig support  ESRI specific map projection parameters 'X_SCALE',
'Y_SCALE', 'XY_PLANE_ROTATION' used in some projections e.g. Krovak.


Thanks
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Re: Overriding existing CRS

Andrea Antonello
Hi Peter,
I have used the epsg.properties file exactly for the purposes you need.

In Italy we have for example a 3003 epsg code, but then we have 3 sets
of parameters that lead to a better precision in different parts of
Italy. Since those are always used over 3003, we created 3 new codes
by adding 30031000, 30031001, 30031002 that have modified Bursa Wolf
parameters.

If your projection is a well known in your country you can also think
to add it permanently to uDig. Else you can just change the
epsg.properties file for you particular purpose.

Ciao,
Andrea


On Wed, Feb 22, 2012 at 11:37 PM, "Peter Mozolík (Gmail)"
<[hidden email]> wrote:

> Hello,
>
> I'm new to uDig. I have few questions.
>
> 1. Is it possible to override internal definition of existing CRS (e.g I
> want to modify TOWGS parameter). I have found file "epsg.properties" in
> directory <UDIG>/plugins/net.refractions.udig.libs_<version>. I guess its
> purpose is to add new CRS into uDig, but I'm not sure about uDig behaviour
> if I use same code (and eventually name) as already defined CRS.
>
> 2. Could you please exaplain how internal db of CRS definitions is built, I
> mean if there is some automatic process to build internal db from official
> epsg registry. How often is internal database of CRS updated?
>
> 3. Does uDig support  ESRI specific map projection parameters 'X_SCALE',
> 'Y_SCALE', 'XY_PLANE_ROTATION' used in some projections e.g. Krovak.
>
>
> Thanks
> _______________________________________________
> udig-users mailing list
> [hidden email]
> http://lists.refractions.net/mailman/listinfo/udig-users
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Re: Overriding existing CRS

"Peter Mozolík (Gmail)"
Hello Andrea,

Thank you for your reply.

Ok, I understand that you have used "epsg.properties" file to add three
new custom CRS definitions into uDig. My original question was if custom
CRS definition from "epsg.properties" file overrides internal definition
of CRS of uDig, provided that I will use the same code.

The problem you described with 3 different sets of parameters is related
to more general problem of uDig. I think that the problem is that
definition of CRS should be separated from definitions of
TRANSFORMATIONS. Then you could have relation 1:N.

Please could you check the other questions from original post.

Tahnk you very much.

Dňa 23. 2. 2012 9:22, andrea antonello wrote / napísal(a):

> Hi Peter,
> I have used the epsg.properties file exactly for the purposes you need.
>
> In Italy we have for example a 3003 epsg code, but then we have 3 sets
> of parameters that lead to a better precision in different parts of
> Italy. Since those are always used over 3003, we created 3 new codes
> by adding 30031000, 30031001, 30031002 that have modified Bursa Wolf
> parameters.
>
> If your projection is a well known in your country you can also think
> to add it permanently to uDig. Else you can just change the
> epsg.properties file for you particular purpose.
>
> Ciao,
> Andrea
>
>
> On Wed, Feb 22, 2012 at 11:37 PM, "Peter Mozolík (Gmail)"
> <[hidden email]>  wrote:
>> Hello,
>>
>> I'm new to uDig. I have few questions.
>>
>> 1. Is it possible to override internal definition of existing CRS (e.g I
>> want to modify TOWGS parameter). I have found file "epsg.properties" in
>> directory<UDIG>/plugins/net.refractions.udig.libs_<version>. I guess its
>> purpose is to add new CRS into uDig, but I'm not sure about uDig behaviour
>> if I use same code (and eventually name) as already defined CRS.
>>
>> 2. Could you please exaplain how internal db of CRS definitions is built, I
>> mean if there is some automatic process to build internal db from official
>> epsg registry. How often is internal database of CRS updated?
>>
>> 3. Does uDig support  ESRI specific map projection parameters 'X_SCALE',
>> 'Y_SCALE', 'XY_PLANE_ROTATION' used in some projections e.g. Krovak.
>>
>>
>> Thanks
>> _______________________________________________
>> udig-users mailing list
>> [hidden email]
>> http://lists.refractions.net/mailman/listinfo/udig-users
> _______________________________________________
> udig-users mailing list
> [hidden email]
> http://lists.refractions.net/mailman/listinfo/udig-users
>
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Re: Overriding existing CRS

Jody Garnett-2
In reply to this post by "Peter Mozolík (Gmail)"
1. Is it possible to override internal definition of existing CRS (e.g I
want to modify TOWGS parameter). I have found file "epsg.properties" in
directory <UDIG>/plugins/net.refractions.udig.libs_<version>. I guess
its purpose is to add new CRS into uDig, but I'm not sure about uDig
behaviour if I use same code (and eventually name) as already defined CRS.

Yes but not well. You can use additional epsg.properties files a indicated. I think You can also place one of these in your application configuration folder (for definitions specific to your organisation). 

2. Could you please exaplain how internal db of CRS definitions is
built, I mean if there is some automatic process to build internal db
from official epsg registry. How often is internal database of CRS updated?
It is the official epsg database; converted from access to HSQL or H2 format. There is a script in the geotools project that does the conversion.

The data model for the database remains unchanged; the script only "corrects" a few database specific things. 

3. Does uDig support ESRI specific map projection parameters 'X_SCALE',
'Y_SCALE', 'XY_PLANE_ROTATION' used in some projections e.g. Krovak.
The WKT parsing engine translates ESRI and Oracle definitions as required.

References:
- http://docs.geotools.org/latest/userguide/library/referencing/index.html
- http://docs.geotools.org/latest/userguide/library/referencing/faq.html
- http://docs.geotools.org/latest/userguide/library/referencing/internal.html

Jody

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