My goal is to calculate the area of mangrove cover (vector layer) per grid cell (vector layer) over time (yearly), to determine land cover change.

grid and polygon layers

I have tried two ways so far. Initially I wanted to Intersect the grid and polygon layers then dissolve by ID and then calculate the area. This has two problems 1) it does not include any grid cells with 0 mangrove polygon intercept, and 2) there are duplicated grid ID values where two polygons intercept the same grid.

grid ID

I also tried Union. This includes the grid cells with 0 mangrove polygon, but still has the issue with duplication.

grid splitting?

excel spreadsheet

Any ideas on how I can avoid this duplication so that I have the same number of grid cells per year so that I can compare between years?


The solution I came up with in the end is as follows.

I Intercepted the grid and mangrove polygon layers, calculated the area and joined the attributes table with the grid attributes table by ID. Then I cleaned the dataset as necessary.

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