Many (but not all) "area" fields have value "2147483647". (https://developer.mapsense.co/tileViewer/?tileset=mapsense.demographics lists it as type string, but I think it should be integer.
Should we correct these values, or remove the field? I think it is important to have for things like population density.
If we have this field we should also document the units. I vote for sq km.
We should also be careful to calculate areas in equal-area projections--web mercator (900913/3857) are very distorted. Something like Behrman (a cylindrical equal area) is good:
+proj=cea +lon_0=0 +lat_ts=30 +x_0=0 +y_0=0 +datum=WGS84 +ellps=WGS84 +units=m +no_defs
I'm not sure if it has an official epsg code, but my local ogr proj4 had it as 3975.
Tests for Alaska:
sqkm_3857 (web-mercator/900913) = 8,138,968.9
sqkm_5070 (Albers North America conic equal area) = 1,505,330.4
sqkm_3975 (Behrman cylindrical equal area) = 1,505,326.6
wikipedia fwiw: 1,717,856 km2 - 13.8% water = 1,481,307.2
mapsense: 2,147,483,647.0 ??
Many (but not all) "area" fields have value "2147483647". (https://developer.mapsense.co/tileViewer/?tileset=mapsense.demographics lists it as type string, but I think it should be integer.
Should we correct these values, or remove the field? I think it is important to have for things like population density.
If we have this field we should also document the units. I vote for sq km.
We should also be careful to calculate areas in equal-area projections--web mercator (900913/3857) are very distorted. Something like Behrman (a cylindrical equal area) is good:
+proj=cea +lon_0=0 +lat_ts=30 +x_0=0 +y_0=0 +datum=WGS84 +ellps=WGS84 +units=m +no_defs
I'm not sure if it has an official epsg code, but my local ogr proj4 had it as 3975.
Tests for Alaska:
sqkm_3857 (web-mercator/900913) = 8,138,968.9
sqkm_5070 (Albers North America conic equal area) = 1,505,330.4
sqkm_3975 (Behrman cylindrical equal area) = 1,505,326.6
wikipedia fwiw: 1,717,856 km2 - 13.8% water = 1,481,307.2
mapsense: 2,147,483,647.0 ??