Hi,
You wrote:
"I'm using a cascading WMS (from another Geoserver) to put a map behind our GPS
station locations and I had to switch all the coordinates to make the
projections overlay correctly."
Could you explain why do you think that WKT definition is the reason for your
trouble with cascading WMS and what coordinates you need to switch? Cascading
WMS is usually painless if user remembers that for WMS versions prior 1.3 the
BBOX is expressed always in longitude-latitude / easting-northing order for all
the projections. In WMS 1.3 the official axis order is to be honoured. Could
it be that you are cascading WMS 1.1.x and you make a wrong assumption that
BBOX should be in lat-lon order? If that is the case, simply start cascading
WMS 1.3.0.
-Jukka Rahkonen-
________________________________
Lähettäjä: Gavin Medley <med...@unavco.org>
Lähetetty: 1. elokuuta 2017 20:15
Vastaanottaja: geoserver-users@lists.sourceforge.net
Aihe: [Geoserver-users] EPSG:4326 Incorrect WKT - Coordinates Reversed!
Hi all,
I believe that the WKT for EPGS:4326 in Geoserver is incorrect. Can someone
verify?
Note the lat lon coordinate order in the following strings. Geoserver displays:
GEOGCS["WGS 84",
DATUM["World Geodetic System 1984",
SPHEROID["WGS 84", 6378137.0, 298.257223563, AUTHORITY["EPSG","7030"]],
AUTHORITY["EPSG","6326"]],
PRIMEM["Greenwich", 0.0, AUTHORITY["EPSG","8901"]],
UNIT["degree", 0.017453292519943295],
AXIS["Geodetic longitude", EAST],
AXIS["Geodetic latitude", NORTH],
AUTHORITY["EPSG","4326"]]
However, epsg-registry.org<http://epsg-registry.org> lists the official WKT as:
GEODCRS["WGS 84",
DATUM["World Geodetic System 1984",
ELLIPSOID["WGS 84",6378137,298.257223563,LENGTHUNIT["metre",1.0]]],
CS[ellipsoidal,2],
AXIS["latitude",north,ORDER[1]],
AXIS["longitude",east,ORDER[2]],
ANGLEUNIT["degree",0.01745329252],
ID["EPSG",4326]]
According to EPSG, latitude is FIRST. I'm using a cascading WMS (from another
Geoserver) to put a map behind our GPS station locations and I had to switch
all the coordinates to make the projections overlay correctly.
-Gavin
--
Gavin Medley
Software Engineer I
UNAVCO
6350 Nautilus Drive
Boulder, CO 80301-5394
med...@unavco.org<mailto:med...@unavco.org>
--- Begin Message ---
On Tue, Aug 1, 2017 at 8:09 PM, Gavin Medley <med...@unavco.org> wrote:
> Hi,
>
> I'm using 1.1.0. Shouldn't the axis order be defined by the EPSG official
> WKT string? Am I correct in thinking that order[1] and order[2] specify the
> coordinate order?
>
OGC took its dear time to make things clear on this, WFS 1.1 happened
midway when the axis order storm blew up (and I'm
partially to blame cause I raised exactly your question, shouldn't WGS84 be
in lat/lon order?).
When that happened everybody on the user side quietly assumed a "sane"
"east/north" order for everything, in GeoServer we tried to
keep both parties happy by adopting the following policy
http://docs.geoserver.org/latest/en/user/services/wfs/basics.html#axis-ordering
Basically, legacy naming, east/north, new naming, EPSG database suggested
order instead.
Deegree seems to have followed suit,
https://github.com/deegree/deegree3/wiki/Axis-order-handling
There is currently no way to get EPSG suggested axis order with the old
EPSG:XYWZ syntax, nor any plan to add one
(but with funding or contribution, that might still happen, as a
configuration flag for those that want to impose strict behavior).
Mind, the axis order issue is far from being solved, even today and with
the latest OGC specs:
- Some outputs only work and make sense in east/north order, and the
spec allows no official way to get them (e.g, shapefile, but also, geojson
and, hear hear, geopackage, and by spec too, see
https://github.com/opengeospatial/geopackage/issues/54)
- I'm constantly asked by customers how the heck one can get east/north
data out of the latest specs (thankfully we have a way)
- Large installations on big companies guide their users to force a
lon/lat order, see for example
https://dgcsportal.readme.io/docs/web-feature-service
- Some epic blog posts raised the issue among disgruntled people:
http://dmorissette.blogspot.it/2012/12/dont-upgrade-to-wms-130-unless-you.html
Long story short, in these conditions, it's best not to take sides and
allow both desired behaviors (in the two different camps) to happen.
If you're in the "pure OGC" camp feel free to contribute an extra
configuration flag to get your GeoServer installation to force EPSG order
no matter what the syntax is, it will be welcomed (by some, at least :-p ).
See a guide to get new features in here:
https://github.com/geoserver/geoserver/wiki/Successfully-requesting-and-integrating-new-features-and-improvements-in-GeoServer
Hopefully one day OGC will wake up and realize that depending on the
context and background both axis orders make sense/are needed, and will
create a syntax allowing to advertise the order without assuming a local,
or network accessible copy of the EPSG database, and an official way to ask
the data in the preferred order.
Hope this helps
Regards,
Andrea Aime
==
GeoServer Professional Services from the experts! Visit http://goo.gl/it488V
for more information.
==
Ing. Andrea Aime
@geowolf
Technical Lead
GeoSolutions S.A.S.
Via di Montramito 3/A
55054 Massarosa (LU)
phone: +39 0584 962313
fax: +39 0584 1660272
mob: +39 339 8844549
http://www.geo-solutions.it
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