Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Use the GeographicLib routines exposed through PROJ for all ellipsoidal calculations #41726

Merged
merged 6 commits into from Feb 25, 2021

Conversation

nyalldawson
Copy link
Collaborator

@nyalldawson nyalldawson commented Feb 22, 2021

Since GRASS upstream is moving away from the previous calculations which
all of QGIS' ellipsoidal distance/areas formulas are based on, let's
follow suit and delegate all these calculations to the GeographicLib
routines exposed through the PROJ api.

Refs OSGeo/grass#1283

calculations

Since GRASS upstream is moving away from the previous calculations which
all of QGIS' ellipsoidal distance/areas formulas are based on, let's
follow suit and delegate all these calculations to the GeographicLib
routines exposed through the PROJ api.

Refs OSGeo/grass#1283
nyalldawson added 4 commits Feb 22, 2021
While these results are very different to the previous reference values,
the geometries measured are extremely narrow polygons which range
from ~-45 to ~45 degrees latitude, and accordingly large variations
are expected depending on the area/length measurement formula
used.

Results have been checked against the R geosphere library and
PostGIS geography type measurements, and match the measurements
calculated using those packages (which are also based on GeographicLib
calculations).
@nyalldawson
Copy link
Collaborator Author

@nyalldawson nyalldawson commented Feb 23, 2021

Anyone cares to review this one?

nirvn
nirvn approved these changes Feb 24, 2021
Copy link
Contributor

@nirvn nirvn left a comment

The code changes look fine to me, the updated test results are reasonable, and the motivation behind this PR very good.

So +1 to merge, especially great we can merge it at the beginning of the dev cycle.

m-kuhn
m-kuhn approved these changes Feb 25, 2021
@nyalldawson nyalldawson merged commit 5caa388 into qgis:master Feb 25, 2021
17 checks passed
@nyalldawson nyalldawson deleted the geographic_lib branch Feb 25, 2021
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Labels
None yet
Projects
None yet
Development

Successfully merging this pull request may close these issues.

None yet

4 participants