g = (450-m) - int((450-m) / 360) * 360 where m = mathematical angle (0 east, anti-clockwise) and g = geographic angle (0 north, clockwise)
On Mon, Dec 6, 2021 at 11:02 AM <[email protected]> wrote: > Dear colleagues on the QGIS user list, > > have an urgent problem with the representation of arrows with a data > defined angle in QGIS. > > Up to now the free GIS world lived with angles assuming north being 0, > east being 90 degrees and so on clockwise until reaching north again (which > might be 360 degrees as well). At least QGIS and many other GIS programs > work such a way. > > But: Now I have encountered a new version - probably created in the ESRI > world, perhaps for harassment or to create a distinctive new feature. This > is called an arithmetic angle, having East for 0 degree, North for 90 > degrees and so on counter-clockwise ! > Actually I it's somehow hard to preserve my humour for this invention. > > Is there a simple possibility to recalculate the "normal" northed angles > to the "arithmetic" easted angles ? It's not that easy, because the > rotation is counter-clockwise. > > Should very urgently prepare some maps with flow arrows in QGIS which > normally assumes northed (geographical) angles .... The values got > automatically exported from a simulation software with the arithmetic angle > system, can't change that. By the way this is meanwhile also demanded by > south german agency as an output specification. > > Has somebody a clue how to solve such a problem in QGIS or how to > recalculate from one to the other system ? Have about 5000 values, so > little chance to get this done manually. At least not in time. > > Thanks a lot for a soon feed back, > Christine > > _______________________________________________ > Qgis-user mailing list > [email protected] > List info: https://lists.osgeo.org/mailman/listinfo/qgis-user > Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user > -- Richard W. Greenwood www.greenwoodmap.com
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