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I found several questions in regard of reprojecting data into a CRS with unit of meters and what CRS to use. Usually the counter question is, "for what region, on what scale" and there the discussions stops. I have tried finding a good CRS myself, but as I am no expert on these things, this whole CRS business is extremely confusing.

So, I am looking for a good CRS with units in meters for: Central Germany, a town called Paderborn. The Region of interest is quite small, ca. 15km around Paderborn.

What do I want to do (and how do I do it currently)?

I create noise simulations for wind turbine parks. So, I have point data (currently in EPSG:3857) for wind turbines. Then, in a python script, I create a equidistant grid around those points, calculate the noise levels on those grid points, use contour-methods to create "isophones" (lines with identical noise level, e.g. 45dBA) and save this data as line or polygon data.

Generally, this all works very nice and gives beautiful results.

But the really dirty part is this: In my script I take the EPSG:3857 data and transform it into EPSG:4326. Then I use a self coded haversine transform to use the already transformed data into "my grid" with an origin I choose. I run the simulation, do the analysis, use again a self coded inverse haversine transform to EPSG:4326 and the transform again back to EPSG:3857.

That probably is not a good idea...

Any recommendations?

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I suggest to use EPSG:25832 ETRS89 / UTM zone 32N, because the Gauss-Krueger DHDN CRS zones are based on the old bessel ellipsoid, and you have to apply a datum shift that is not constant over the whole of Germany.

ETRS89 has no datum shift to EPSG:4326 WGS84 which you can get from GPS receivers, and all official cadastral information has beeen moved to ETRS89 by now.

You could set up a local transverse mercator projection on a center point of your area of interest as well, but that would gain only little improvement on accuracy against UTM.

By the way, EPSG:3857 has no real meters as units, they match only at the equator.

  • Thank you for the information. I tried it with ETRS89 and this works as a charm as well. Wow, this CRS stuff is complicated. It would really have been much easier if the earth was flat. As til_b suggested to avoid Gauss Krüger as well, I will mark yours as the correct answer. – user2532323 Oct 12 '15 at 8:50
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I'd use whatever is the official CRS in Germany: http://crs.bkg.bund.de/crseu/crs/eu-description.php?crs_id=Y0RFX0RIRE4gLyBHS18z

For posterity's sake, some Gauss-Krueger projection like 31466, 31467, 31468 or 31469 (one per zone). Your town falls into zone 2 (ESPG:31467): http://georepository.com/crs_31467/DHDN-3-degree-Gauss-Kruger-zone-3.html

  • Thank you very much. This works like a charm. Although, now by comparison, my dirty approach was quite accurate, this is a much cleaner and better solution. – user2532323 Oct 11 '15 at 18:42
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    Please don't use Gauss-Krüger for new data. Please use UTM. Gauss-Krüger is supposed to vanish sometime in the future (think of it as deprecated). – til_b Oct 12 '15 at 6:53

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