Re: [Geotools-gt2-users] Geotools Maven versions for JTS 12-SNAPSHOT and bug GEOT-4795

[Eric H. <er...@he...>]

Andrea,

Thanks much for the info and all the help.  I think our accuracy can be in
the 30 meter range, probably more like 100 meters.

Eric.


On Sat, Aug 2, 2014 at 1:52 PM, Andrea Aime <and...@ge...>
wrote:

> Eric,
> please make sure to include the mailing list when answering mails.
>
> On Sat, Aug 2, 2014 at 7:41 PM, Eric Holsinger <er...@he...> wrote:
>
>> I realized I had been putzing around with my code trying to figure that
>> bug out, and had changed my original attempt (EPSG:32630) to default
>> cartesian.  Mistake on my part.  I realize I need a projected coord sys
>> conversion vs. geographic.
>>
>> So, now that I've figured out the correct geotools version + JTS version,
>> added the gt-epsg-hsql dependency to maven (in addition to
>> gt-epsg-extension dependency), I've been able to pull in the EPSG:32630,
>> run it against the now-patched bug I was experiencing before - and it seems
>> to work.
>>
>> My question for you would be:  can I use EPSG:32630 planet-wide to
>> perform meters calcs if my source CRS is WGS84?  If not, will I have to
>> change the CRS over different areas of the globe, based upon where I want
>> to perform the calc?  Is there a "standard EPSG WKT" that most people use
>> for calc'ing meters from WGS84 source for transforms - and if so, can you
>> give me the EPSG ID number?
>>
>
> EPSG:32630 is a UTM zone 30N, it has a "small" area of validity:
> http://prj2epsg.org/epsg/32630
>
> Generally speaking, there is no projection that can cover the world and
> that gives you very good distance
> accuracy everywhere.
>
> I believe the closest thing to a usable world projection is a world equal
> area, such as Eckert IV or
> Mollweide, but none of them has an official entry in the EPSG database,
> see:
>
> http://www.geo-solutions.it/blog/developers-corner-adding-two-global-equal-area-projections-to-geotoolsgeoserver/
>
> You can try them and see if they give you enough precision for your use
> cases.
>
> If instead you need high accuracy (e.g. meter level) then I believe there
> is no other option but
> creating a custom local projection centered on the geometry you have to
> reproject, as the center
> of the projection is the one that normally has the least deformation.
> You can use the WMS auto projections to create your local projection (see
> the OGC WMS spec,
> it has the syntax.
> As an example, "AUTO:42001,9001,-93,0" is a transverse mercator using -93
> as the
> central meridian
>
> Cheers
> Andrea
>
> --
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>
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