Land/built-up

Using 'population' data to estimate built-up land

Some inner cities can be quite dense, but even the less-dense suburbs are still fully built-up, as none of the land is truly wilderness (...)( even the parks and nature trails are heavily touched by humans ), and none of it is considered farm land (...)( maybe this could change with suburban farming, but even then, maybe double-counting the same land (as both cropland and built-up land) is ok ).

Let's estimate the minimum population density that might be considered fully built-up land:

suburban_lot_size

5000 ft^2

"Large, 5,000 square foot lots, on the other hand, are the standard in US post-war suburbs."

Do Minimum Lot Size Rules Matter? - Strong Towns www.strongtowns.org › journal › do-minimum-lot-size-rules-matter

housing_fraction

40%

What fraction of the suburban land is housing

The rest would be roads, parks, parking lots, and a small number of commercial buildings.

This is just an educated guess, so if you have actual data, please say it in the Template:TALKPAGENAME.

household_size

3 people

Average number of people living in a house, in our low-density suburb

This is intentionally a low estimate because we want to know the minimum population density for fully-built-up land.

people per km^2 (calculation loading)

So, any land with more people than this, would be considered 100% built-up land in our analysis.

Any land with fewer people, will be counted proportionally. So if the population density is 10% of the threshold, we say the area contains 10% built-up land. This might be the case of a small family farm, where 90% of the lot is farm land, and the last 10% is housing and driveway.

Technically, there could be fully-built-up areas below this population threshold - such as industrial areas - but those are probably uncommon enough.
Let's test out our threshold using the image generator:

pop << data/population.data-float64-8640x4320 # population counts
pop @@ quantity_to_density # convert to 'people per km^2'
pop /= 5000                # threshold for land to be considered 'fully built-up'
pop <= 1
pop @@ density_to_quantity
pop @@ stats

The "sum" (which will appear in the result from the last line) will be the number of km^2 of built-up land on Earth.

Compare this to official estimates...