Eric,
please make sure to include the mailing list when answering mails. 

On Sat, Aug 2, 2014 at 7:41 PM, Eric Holsinger <eric@heregear.com> 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

--
==
GeoServer Professional Services from the experts! Visit
http://goo.gl/NWWaa2 for more information.
==

Ing. Andrea Aime 
@geowolf
Technical Lead

GeoSolutions S.A.S.
Via Poggio alle Viti 1187
55054  Massarosa (LU)
Italy
phone: +39 0584 962313
fax: +39 0584 1660272
mob: +39  339 8844549

http://www.geo-solutions.it
http://twitter.com/geosolutions_it

-------------------------------------------------------