I'm getting strange results with area calculations via the field calculator, when I'm working with a geopackage file. The field calculator is returning a negative values for some of the polygons. I can get it to return the (apparently) correct values by saving the layer as a shapefile, and using the same calculation.
Is there a way to correct this behavior without exporting the layer to a different format, or do I need to avoid geopackages when manipulating data?
This is similar to the problem in some other posts: Why do area calculations return negative values? Area is calculating wrong using $area in field calculator (QGIS 2.8.1-Wien) Wrong $area from field calculator (QGIS)
The file I'm having trouble with is a selection of parcels from a larger parcel data set with parcels within a limited extent merged by owner: https://www.dropbox.com/s/nwgg8stxrglcdn8/MergedParcels.gpkg?dl=0
There are multi-part features in the file, but I still get the negative values after using multi-part to single part vector geometry tool.
I'm using QGIS 2.18.2 on a Windows computer. My project is in EPSG: 102748 (Washington State Plane North- US Feet), as is the geopackage.
I'm getting the same results with On-the-fly projection both on and off. The formula I'm using in the field calculator is:
My project properties are set to calculate areas and distances in map units (feet/square feet).