Calculating frequency of polygon types overlapping coordinate point

Question

I have shapefiles of sea ice coverage for multiple days of the year. At each time-point (day) the sea ice is split into different polygons which corresponds to different ice types (i.e. fast ice, consolidated ice, etc). I have four coordinate points and I would like to obtain the frequency or the counts of the different polygon types occurring at those specific coordinates along the whole year.
Is there a way to do this in QGIS?

Kazuhito · Answer

This approach is probably tedious -- not recommended if there is another way.
(1) "Split Vector Layer" tool to split the original layer to 6 layers as per the type of ice.
(2) Run Union tool (in the Processing Toolbox > Vector geometry) to divide polygons at overlaps.

(3) This returns a new layer 'Union'. As the attribute table of 'Union' shows only the original polygon id, we need to calculate counts by an expression count("id", group_by:= geom_to_wkt($geometry)).

(4) Lastly, activate Identify Features tool and click on your observation point to find the counts.

(5) Problem is, you have to repeat above process 6 times (for whole ice classes)... ...

Calculating frequency of polygon types overlapping coordinate point

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