Wow that NZTM situation is a mess; getting the wrong definition into the
EPSG database takes some skill.
Can you construct the WKT representation of what you need (to match your
data as provided) and then use GeoTools to reproject to your final answer?
I have found that making special cases based on axis order makes my head
hurt, and if I set up my definitions correct GeoTools can construct the
required transform ...
--
Jody Garnett
On 6 December 2016 at 17:44, Iain Matcham <[email protected]> wrote:
> Hi all,
>
> I have an application where I want a user to be able to enter a set of
> bounds and a CRS and then the code will reproject their input into a
> default CRS for further processing. A fairly simple operation:
>
> public ReferencedEnvelope getEnvelope(
> double minEast, double maxEast,
> double minNorth, double maxNorth,
> CoordinateReferenceSystem crs) throws TransformException,
> FactoryException {
> Envelope envelope = new Envelope(minEast, maxEast, minNorth,
> maxNorth);
> ReferencedEnvelope refEnv = ReferencedEnvelope.create(envelope, crs);
>
> return refEnv.transform(DEFAULT_CRS, true);
> }
>
> Except for NZTM. Thanks to LINZ, NZTM is has an axis order y/x. The
> above code falls over.
>
> Following this (admittedly quite old) thread:
> http://osgeo-org.1560.x6.nabble.com/Need-help-reprojecting-
> ReferencedEnvelope-td5069254.html
> to the suggested resolution seems to be to "Make a special case for
> NZTM". Extending this to "make a special case for any y/x CRS" means my
> code now looks like:
>
> public ReferencedEnvelope getEnvelope(
> double minEast, double maxEast,
> double minNorth, double maxNorth,
> CoordinateReferenceSystem crs) throws TransformException,
> FactoryException {
>
> AxisDirection axisDir =
> crs.getCoordinateSystem().getAxis(0).getDirection();
> Envelope envelope = axisDir == AxisDirection.NORTH ?
> new Envelope(minNorth, maxNorth, minEast, maxEast) :
> new Envelope(minEast, maxEast, minNorth, maxNorth);
>
> ReferencedEnvelope refEnv = ReferencedEnvelope.create(envelope, crs);
>
> return refEnv.transform(DEFAULT_CRS, true);
> }
>
> which seems like a lot of faff for what should be an easy operation.
> But we haven't even started yet because I am pretty sure this code is
> incomplete. I _think_ the real question is not are we x/y or y/x it is
> are we right handed (x/y) or left handed (y/x). So my code above would
> actually have to handle not just NORTH/EAST (right) and EAST/NORTH
> (left) but also NORTH/WEST (right) or NORTHEAST/SOUTHEAST (left) etc etc
> and so on through all the permutations of AxisDirection.
>
>
> So ... the only sensible resolution I can see without writing an entire
> novel of if/elses for all the possible pairs of AxisDirections is to use
> forceXY, but referring back to the discussion mentioned above, Ben
> strongly discourages this.
>
> Does anyone have any suggestions how this can be handled in a generic
> non-complex way without forcing x/y axis ordering? Hopefully someone can
> help.
>
> If not can I suggest a method
>
> ReferencedEnvelope.create(Envelope env, CoordinateReferenceSystem crs,
> boolean envelopeIsGeometric)
>
> which (if arg2 is true) treats the envelope as x/y and does any
> necessary axis conversion internally so that this piece of code can be
> written once and doesn't need to be written by anyone and everyone who
> might need NZTM in their app?
>
> Would anyone else find this useful?
>
> Thanks
> Iain
>
> --
> Sent from my ZX80
>
>
> ---
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>
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