[Qgis-developer] QGIS API Distance, Azimuth/Bearing - API Documentation

Martin Dobias wonder.sk at gmail.com
Thu Apr 13 05:35:05 PDT 2017

Hi Calvin

On Mon, Apr 3, 2017 at 11:00 PM, C Hamilton <adenaculture at gmail.com> wrote:
> I had been wondering what algorithm is being used for the methods azimuth,
> distance, and  project in the QgsPoint class, but in looking at the code it
> is simply cartesian plane math. It looks like the qgsdistancearea class is
> using vincinty math if I am examining the code correctly.
> Vincinty is more accurate than the great circle, but fails in some cases and
> there are more accurate methods. I apologize if I have failed to find the
> right classes and methods in the API, but why doesn't the API provide the
> more accurate geodesic calculations that are in geographiclib. It also seems
> like it would be good to also provide great circle math as an option. Am I
> missing it in the API or is it simply not there? If it is not there is
> anyone working on adding it?

QgsDistanceArea is currently the only class in QGIS for doing
measurements - either euclidean or using Vincenty's formulae. I have
not heard about anyone currently working on adding more methods for
calculation of distances or areas. I am no expert in geodesic
calculations - what other methods would you like to have in QGIS and
how are their results different from Vincenty's formulae?

> Are there any efforts going on to flesh out the QGIS API a little more.
> Generally, the methods and parameters are not well documented if it is not
> obvious from the name.

Nowadays there is quite a lot of effort being done to improve QGIS API
for the upcoming release of 3.0. Please feel free to join the effort
and submit pull requests on this topic - that would be very


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