Just got started with QGIS (the software) today and I'm getting Null for a hand-drawn polygon, even for a circle shape. Here is what I've done:

  1. Installed QuickMapServices plugin
  2. Installed GeoCoding plugin
  3. Created new Project
  4. Added ESRI Satellite ArcGIS/WorldImagery 3857 layer
  5. Added Scratch Temp layer also 3857 (later a shapefile layer)
  6. Proceeded to draw an irregular hand-drawn polygon (later circle)
  7. Added area field, decimal, 10, 2
  8. Open attribute table but resulting area is NULL

As mentioned I've tried creating a shapefile layer and drawing a simple circle shape as well with the same area field params but still get NULL.

Not sure if its relevant but I'm following this video tutorial:https://www.youtube.com/watch?v=7vwQ0o_t4XQ

Did I miss a parameter somewhere that I needed to configure?

  • 2
    Just adding a field called "Area" doesn't automatically tell QGIS to calculate the area. You can use the field calculator to calculate the area.
    – user2856
    Commented May 28, 2023 at 22:24
  • 2
    gis.stackexchange.com/a/30008/2856 but note that EPSG:3857 is a poor choice for calculating areas and will give you very inaccurate results, particularly at higher latitudes. Suggest you use an equal-area CRS appropriate for your area of interest.
    – user2856
    Commented May 28, 2023 at 22:48
  • Ok i figured out I had to create the field using the calculator and selecting the $area function. Now is there a way to have it update the area after i edit the polygon? Cause I find myself having to update it manually with the field calculator.
    – marciokoko
    Commented May 28, 2023 at 23:15
  • Which CRS do you suggest for more accurate readings?
    – marciokoko
    Commented May 28, 2023 at 23:17
  • 1
    An equal-area or UTM CRS appropriate for your area of interest, look at epsg.io. Re update, gis.stackexchange.com/a/389727
    – user2856
    Commented May 29, 2023 at 0:45


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