I have a question - this didn't seem to be an issue until 2.18.12 QGIS.
I'm currently on 2.18.13 Ubuntu 17.04. I could be missing something.
I have a forestry client and they were preparing to do some aerial
spraying. So I outlined the area to be sprayed and generated acres.
Generally I set my project properties to feet (for units) and square
feet (for area) and the ellipsoid set to none/planimetric. My data is
stored in WGS84 in postgis. I pulled it out into a shapefile and
eventually stored it in geopackage while trying to track down my issue.
Dropbox link to the data:
https://www.dropbox.com/sh/8w1spcxu5by7z70/AACilL5kOeOC7tzX4WCEkOdka?dl=0
I set the CRS to EPSG:2274 - the data is in wgs84.
If I run acres with project properties set to feet, square feet, and
none/planimetric and using the Field Calculator I get: 372.82 acres.
This is wrong.
If I run acres with project properties set to feet, square feet, and
wgs84 as the ellipsoid I get 307.41 acres which appears to be right.
If I run acres using the virtual layer abilities: /select
sum(st_area(st_transform(geometry,2274))/43560) from spray/ I get 306.04
acres which may be right.
I didn't notice this until 2.18.12 - I updated to 2.18.13 and it is
still acting "odd" - I didn't notice in 2.18.11 but I'm not sure if I
ran any area calculations in 2.18.11. I have also noticed that if I
switch from wgs84 (feet, square feet, none for ellipsoid in the project
properties) and then switch to EPSG:2274 the ellipsoid changes to
grs1980(iugg 1980)...... which having the ellipsoid at GRS80 may have
been covering for my area calculations and making them "about right".
Anyway thoughts? Ideas? Am I doing something wrong?
Randy
--
Randal Hale
North River Geographic Systems, Inc
rjh...@northrivergeographic.com
(423) 653-3611
https://www.northrivergeographic.com
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