Polygon on scratch or shapefile area returns null in QGIS & EPSG3857

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Asked 6 months ago

Modified 6 months ago

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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:

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?

user2856

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asked May 28 at 19:37

marciokoko

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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
May 28 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
May 28 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
May 28 at 23:15
Which CRS do you suggest for more accurate readings?
– marciokoko
May 28 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
May 29 at 0:45

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