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Has anyone come across a free web service / REST API to transform coordinates?

I'm particularly interested in transforming from WGS84 to: New Zealand Geodetic Datum 2000 (NZGD2000 / NZTM) and New Zealand Geodetic Datum 1949 (NZGD1949 / NZMG). Would be a bonus if I could also get the grid version of coordinates as well.

Perhaps there's a JavaScript / C# library out there that I can use and host my own service?

Apologies if I'm slightly out with my terminology - I'm still a little green to GIS.

Thanks in advance for any advice, Gavin

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up vote 2 down vote accepted

You can use Proj4JS to do the conversion in the browser: either pass it EPSG codes (EPSG:2193 for NZGD 2000, EPSG:27200 for NZGD 1949). They have a user guide with further details of its configuration.

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Thanks scw - perfect fit once I used WGS84 as the source instead of EPSG:4236 they gave in their example code. – Gavin May 21 '11 at 7:48
perhaps let them know they have a typo, I'm guessing they meant to put EPSG:4326 which is the correct code for WGS84. – scw May 22 '11 at 18:30
They have both EPSG:4326 and WGS84 - seem to be slighly different definitions though. – Gavin May 22 '11 at 20:50
But yes, does look like a typo on example. Was getting confused myself! Can't find any contact options or registration options to get in contact with the project creators though to let them know. – Gavin May 23 '11 at 23:21
Note that Proj4JS doesn't use the grid-based conversion, so its accuracy is limited to +/- 4m according to LINZ – rcoup Jun 8 '11 at 2:18

I use all the time...

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We're looking for long answers that provide some explanation and context. Don't just give a one-line answer; explain why your answer is right, ideally with citations. Answers that don't include explanations may be removed.

+1 good service. – 5chdn Oct 27 '14 at 9:17

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