[MetaCRS] Re: [OpenLayers-Dev] New Zealand Map Grid in OpenLayer and Proj4js

[Richard Greenwood]

NZGD49 to WGS84 is a grid shift datum transform. Proj4js/cscs does not
have grid shift functionality.


On Tue, Sep 30, 2008 at 11:30 AM, Mike Adair <madair at dmsolutions.ca> wrote:
> Hi Stephen,
>
> I've added the NZMG code to Proj4js (http://trac.osgeo.org/proj4js/ticket/1)
> but there is a couple of problems:
>
> -  I'm not a licensing expert but we can't use the GPL license for this
> because it is too restrictive.  Can you change that to LGPL like the rest of
> the library?  If so please put a comment to that effect on the ticket.
>
> - The test points aren't quite matching up, errors are consistent with the
> datum shift you describe in the code.  Can you provide some test points for
> the 2 coordinate systems to WGS84 please?  That will help isolate any
> problems.
>
> Thanks for the contribution.
>
> Mike
>
> Stephen Irons wrote:
>>
>> Thank you. I saw the proj4js Trac website, but there were no tickets
>> entered, so I assumed it was not in use.
>>
>> There is now one ticket open...hope someone else finds the NZMG
>> transformation useful.
>>
>> Stephen
>>
>>
>> On Thu, 2008-07-10 at 09:07 -0400, Mike Adair wrote:
>>>
>>> Cool! We're still in the process of moving the project infrastructure for
>>> proj4js but in the meantime you can enter a ticket and patch in the Trac
>>> system at: http://trac.osgeo.org/proj4js/
>>> And eventually it should make it's way into the code base.
>>>
>>> Mike
>>>
>>>
>>>
>>> Stephen Irons wrote:
>>> > I have implemented a Proj4js transformation for New Zealand Map Grid >
>>> > (NZMG) co-ordinates (EPSG:27200). spatial-reference.org >
>>> > <http://spatial-reference.org> gives a description of the > transformation,
>>> > but the '+proj=nzmg' was not available in the current > version in the
>>> > repository. This projection is not related to any of > the existing types,
>>> > so I implemented it.
>>> >
>>> > I would like to contribute this code to Proj4js. However, it is not >
>>> > obvious how to submit this code to the project. Can anyone here point > me
>>> > to the right place?
>>> >
>>> > Stephen Irons
>>> >
>>> >
>>> > Background
>>> >
>>> > New Zealand Map Grid (NZMG) is a projection used to convert latitude >
>>> > and longitude to easting and northing coordinates in metres. It was >
>>> > designed to minimize the scale error over the land area of New Zealand > and
>>> > cannot be used elsewhere.
>>> >
>>> > The New Zealand govnernment survey agency, LINZ (Land Information New >
>>> > Zealand) has published two series of maps covering the mainland areas > of
>>> > New Zealand.
>>> >
>>> >     * 262-series is 1:250000
>>> >     * 260-series is 1:50000
>>> >
>>> > These maps are available in printed form and are currently the only >
>>> > large-scale maps of New Zealand widely available to the general > public.
>>> > Vector data is also available.
>>> >
>>> > Various commercial concerns have scanned these maps, or generated >
>>> > tiles from the vector data, and released products using these tiles. I >
>>> > have one of these products and want to use the tiles with OpenLayers.
>>> >
>>> > New Zealand Map Grid
>>> >
>>> > New Zealand Map Grid was designed by Dr W. I. Reilly in 1973. Its >
>>> > official specification is published as /New Zealand Map Grid/, > Department
>>> > of Lands and Survey Technical Circular 1973/32. A scanned > image of the
>>> > publication is available at >
>>> > http://www.linz.govt.nz/docs/miscellaneous/nz-map-definition.pdf
>>> >
>>> > It is also described in /Conversion between Latitude and Longitude and
>>> > > New Zealand Map Grid/, OSG Technical Report 4.1, 1998. This document > is
>>> > available at http://www.linz.govt.nz/docs/miscellaneous/nzmg.pdf
>>> >
>>> > NZMG is given EPSG code EPSG:27200. It is defined at >
>>> > http://spatialreference.org/ref/epsg/27200/proj4/ as
>>> >
>>> >     * "+proj=nzmg +lat_0=-41 +lon_0=173 +x_0=2510000 +y_0=6023150
>>> >       +ellps=intl +datum=nzgd49 +units=m +no_defs"
>>> >
>>> > Now, most of this is known to Proj4js code. However, the projections >
>>> > 'nzmg' is not know, and needs to be implemented.
>>> >
>>> >
>>> >
>>> > ------------------------------------------------------------------------
>>> >
>>> > _______________________________________________
>>> > Dev mailing list
>>> > Dev at openlayers.org <mailto:Dev at openlayers.org>
>>> > http://openlayers.org/mailman/listinfo/dev
>>> >
>>>
>
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-- 
Richard Greenwood
richard.greenwood at gmail.com
www.greenwoodmap.com