Module:Infobox dim

Module documentation[view] [edit] [history] [purge]

Code to convert information about physical size of objects into parameters for geohack or mapframes.

The following parameters describe the physical object size:

• length_km
• length_mi
• width_km
• width_mi
• area_km2
• area_mi2
• area_ha
• area_acre

When producing scale or zoom, module can use size of object on screen specified via |viewport_cm= or |viewport_px=. Defaults to 10cm, to match geohack.

In addition, the module can accept and convert between geohack parameters:

• dim
• scale
• type (e.g., "mountain" or "city")
• population (for type="city" only)

Usage

{{#invoke:Infobox dim|dim}}

Generates dim string (e.g, "24km") suitable for geohack link

{{#invoke:Infobox dim|scale}}

Generates scale (e.g, 100000) suitable for geohack link

{{#invoke:Infobox dim|zoom}}

Generates Open Street Map zoom level (e.g, 12) suitable for use in mapframes

The above documentation is transcluded from Module:Infobox dim/doc. (edit | history)
Editors can experiment in this module's sandbox (edit | diff) and testcases (edit | run) pages.
Subpages of this module.

--[[
geohackTypeToScale

Convert from Geohack's scale and dim levels to OSM style zoom levels as used by <maplink>
]]
local function geohackScaleToMapZoom(scale)
	scale = tonumber(scale)
	if not scale or scale <= 0 then return end
	-- Approximation of https://wiki.openstreetmap.org/wiki/Zoom_levels
    -- pixel/m from OSM is exact, so use zoom level 9 and 0.3 mm/pixel
	return math.log(305.748*ppm/scale)/log2 + 9
end

local function geohackDimToScale(dim, units)
	dim = tonumber(dim)
	if not dim or dim <= 0 then return end
	if units and string.lower(units) == 'km' then
		dim = dim*1000
	end
	-- Using 0.3 mm/pixel from https://wiki.openstreetmap.org/wiki/Zoom_levels, and
	-- assuming dim spans a map width of 800px (= 24cm on screen)
	return ppm/800 * dim
end

--[[
geohackTypeToScale

Convert from Geohack's types to Geohack's scale levels
]]
local function geohackTypeToScale(type, population)
	local typeScale = {
		adm1st = 1000000,
		adm2nd = 300000,
		adm3rd = 100000,
		airport = 30000,
		city = 100000,
		country = 10000000,
		edu = 10000,
		event = 50000,
		forest = 50000,
		glacier = 50000,
		isle = 100000,
		landmark = 10000,
		mountain = 100000,
		pass = 10000,
		railwaystation = 10000,
		river = 100000,
		satellite = 10000000,
		waterbody = 100000,
		camera = 10000
	}
	local scale
	if typeScale[type] then
		scale = typeScale[type]
	end
	population = tonumber(population)
	if type == 'city' and population and population > 0 then
		-- assume city is a circle with density of 1000/square kilometer
		-- compute diameter, in meters
		local diam = 35.68*math.sqrt(population)
		-- convert to scale
		scale = geohackDimToScale(diam)
		-- don't zoom in too far
		if scale < 25000 then
			scale = 25000
		end
	end
	return scale
end