[QGIS-Developer] Geodesic Measure Tool With Bearing Information

C Hamilton adenaculture at gmail.com
Mon Jun 12 07:20:31 PDT 2017

> >
> > 2. I would like to see a check box or selection widget of some sort that
> > chooses between using Geodesic math or the current method of calculating
> the
> > distances which I am still unsure on how it is doing its calculations.
> If you expand down the info box you'll get a detailed description of
> exactly how QGIS is calculating the distances. Is there something
> missing there?

In some sense the measure tool is rather confusing. You can't just use it
without really reading up on how to use it and even then I am not 100% sure
I am getting the results I want, but as I look more into it I also realize
I have had a narrow view on how users might use it.

When you click the configuration button it takes you to the Map Tools
Options. What I didn't initially realize is that there are also project
properties that you also need to set as well. There is not a button on the
measure tool dialog that takes you to that dialog to change those settings.
Can this be simplified some how?

By default it appears that "None / Planimetric" is selected as the
ellipsoid. I think that for many people trying to use QGIS they are not
going to know how to get the settings set correctly to get accurate
measurements. I personally prefer to have the defaults set so that all
measurements make use of the Vincinty algorithm - projecting the
coordinates to latitude and longitudes and then doing that calculation.
This would give relative accurate measurements, but for the user that has a
local projection then they might want to select something else.

By the way there appears to be a problem with selecting Project
Properties->General Ellipsoid settings for QGIS 3. Every time I go into
these settings the Ellipsoid is set to "None / Plainimetric" and it is not
enabled. I have to click on the CRS tab and then go back for it to be

> > Right now it could use the Vincinty algorithms in QGIS to calculate the
> > distances, but eventually I would like to see the geographiclib
> algorithms
> > used.
> I'd start with the bearing changes (since they are self contained, and
> the methods for calculating bearing are already present in the QGIS
> api). Then using geographiclib could be discussed as a separate set of
> changes, to be decided on its own merit. If you mix these two changes
> it's likely to get bogged down as one or other part of the changes are
> debated.

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