I created isochrones using Iso-Area algorithm as polygons in QGIS. Is there any tool in QGIS that helps with calculating areas covered by created polygons?
You can create the area using field calculator:
area ($geometry) will calculate the area for each feature. If you want to get the sum for each group with the same
id, you can use the aggregate function
sum, so your expression will probably look like:
sum ($area, group_by:="id").
The unit of measurements depends on the CRS of your layer, have a look in the layer properties. For the difference between
area($geometry) see the help in the expression editor or here: https://qgis.org/api/2.14/qgsexpression__texts_8cpp_source.html
Returns the area of the current feature. The area calculated by this function respects both the current project's ellipsoid setting and area unit settings. For example, if an ellipsoid has been set for the project then the calculated area will be ellipsoidal, and if no ellipsoid is set then the calculated area will be planimetric.
Calculations are always planimetric in the Spatial Reference System (SRS) of this geometry, and the units of the returned area will match the units for the SRS.