I like this challenge. Of course, Ralf does it every time he does a Live Mapping session. Anyway, I will give it a go tomorrow.

Another non-cat photo of MY mapping assistant

When I was 12, I was obsessed with Lord of the Rings, and wanted to create my own world. Then I went on a school expedition to Norfolk Island, and 'fell in love' with the map of Phillip Island, 5 km south of Norfolk island, and denuded of all vegetation by rabbits imported there by the prison officers for their 'hunting entertainment'. They have actually got rid of the rabbits and the island is being revegetated, but when I visited it in 1964, it was like a moonscape!

Anyway, this is the Google map of Phillip Island, and the first map I ever did (by hand) of the fantasy land of Al'Ayn - again for a book I will never write. And also, the third map is the newer version made when I got CC2, then the fourth when I got CC3+.

As a person who has done a big city with vectors, i can certainly say vectors are slower the bigger the city gets, whereas using pngs means the map has a pointer to that symbol just once, no matter how many times you use the symbol.

If the population is above 20,000, I use the following rule of thumb to work out size. On average, each building has 30 x 30' (or 10x10 m) footprint, with 2 stories. Each 100 M2 houses 4-6 people, thus on average, each 100 m2 houses 8-12 people. So the formula for distance (in square Metres - I just cannot think imperial - we have been metric since 1970's) is Area = Population x100/ people in each 100 m2/ number of stories per building.

So, if you want a sparsely populated city. make it 5 people per 100 m2. Say the population is 50,000. For all single storey buildings of 100 m2 average, that is 10,000 buildings requiring 1,000,000 ie 10,000 x 10,000 m in area.

But make the city more densely packed, say 10 per 100 m2, with average of 2 stories per building, and the area required is greatly reduced. Area = 50,000 x100/10/2 = 250,000 m2, or 500 x 500 m2. Add some extra for very large buildings, and you get an idea of the dimensions required for your city - but remember to add extra to make room for space outside the city walls, or building extents.

In general, for a 50,000 city, I would allow about 1000 x 1000 m dimension (or 1 sq km).

Dun Fingolfin has 16526 buildings, and dimensions (of the city, not the map) of about 6600 x 3100 ft (yes, I used feet for the Atlas to fit in with all you imperials) which is about 35 x 35' per building (close to 10 x 10 m) with average of 2.5 stories per building, and a dense population of 10 per 35x35', that gives a population of Dun Fingolfin of about 413,000. But if I had made it a sparsely populated city with average of only 1.5 stories per building, and only 5 people per 35x35 ', the population would be only 123.000.

So decide what population you want, how many would fit into a 100 m2 space (you will have to work out what this is in sq feet), what the average number of stories per building is, then that works out the number of buildings (Pop/ number per 100m2/average stories per building) and area (no of buildings of 100 m2 average x 100) in m2. Hope this helps you gauge your area and buildings required.