## Calculating Shadowed Edits

The sum of the version number for every visible object in OSM is equal to the total number of (additive) edits to the map. (This is going to be an under-estimation of editing work in OSM becuse it does not count object deletions).

Therefore, at the tile level: (Objects edited in a year) + (Objects edited before year) = Total Objects on tile and the sum of the verisons of all of these objects = number of edits on that tile to date.

If we make the assumption that every edit to an object increments the version number by 1, then in the case where it was incremented by more than one, an edit was subsequently masked. The difference in this number when assuming 1 is the number of masked edits:

```
SUM OF ALL VERSIONS OF OBJECTS ON TILE (The total number of edits on that tile to date)
- TILE VERSION SUM FROM YEAR-1 (The total number of edits on that tile up to this year)
- TOTAL NUMBER OF EDITS THAT YEAR (The number of objects on the tile timestamped in this year)
-------------------------------------------------
THE NUMBER OF SHADOWED EDITS
```

Extending this, we can count the number of specific objects that match this formula and calculate the shadowed buildings, roads, and amenities.

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