[QGIS-Developer] Geodesic Measure Tool

[C Hamilton]

All,

The "Shape Tools" plugin (http://plugins.qgis.org/plugins/shapetools/)
contains a Geodesic Measure Tool that produces results that are the same as
Google Earth. In addition to distance it displays the bearing or heading
between each pair of points. It also rubber bands the geodesic path being
measured. I am hoping that eventually what is in the Geodesic Measure Tool
will be coded into the QGIS measure tool.

The rational for the Geodesic Measure Tool was that I needed the heading
angle, but additionally I really did not like the results I was seeing from
the QGIS measure tool. It is very confusing on how to set the right
ellipsoid to get the proper results. The first challenge is how you even
set the ellipsoid and when you find it, there is a "WGS 84" ellipsoid and a
"WGS84" ellipsoid and the latter one I have no idea what it is producing.
Its measurements are not correct. Personally I think the QGIS measure tool
should have a pull down to be able to select the ellipsoid and a check box
to set it to the most accurate ellipsoid. I spent a lot of time trying to
find where to set the ellipsoid. The Configuration button does not take you
there.

The Geodesic Measure Tool is based on geographiclib which produces the most
accurate results - better than Vincinty and which I hope geographiclib will
eventually be used in QGIS. I consider the Geodesic Measure Tool to be the
gold standard for earth measurements without taking elevation into
consideration.

I have seen a number of posts about measurements in QGIS that has led to a
fair amount of confusion. Somehow the measuring tool need to be made
clearer as to what it is doing. I'm not exactly sure how to do that. Having
too much flexibility can cause issues and in part is why the Geodesic
Measure Tool was produced. It is simple to use for Google Earth like
results.

Calvin
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