Polygon projection in CountryData incorrect?
- To: mathgroup at smc.vnet.net
- Subject: [mg116270] Polygon projection in CountryData incorrect?
- From: "Sjoerd C. de Vries" <sjoerd.c.devries at gmail.com>
- Date: Wed, 9 Feb 2011 02:10:26 -0500 (EST)
CountryData contains a polygon for every country. It can be output in
various projections using a specification like {"Polygon",
"Mercator"}.
However, the resulting polygon doesn't seem to be consistent with a
transformation using GeoGridPosition and GeoPosition.
If I plot Amsterdam using its CityData coordinates transformed with a
Mercator projection it falls outside the Netherland's borders (1st
example below). When I use the alternative approach (2nd example)
everything seems OK. Am I doing something wrong or is this a bug?
Graphics[
{
{FaceForm[], EdgeForm[Black],
CountryData["Netherlands", {"Polygon", "Mercator"}]},
Red, PointSize[0.02],
Point@GeoGridPosition[
GeoPosition[
CityData[{"Amsterdam", "NoordHolland", "Netherlands"},
"Coordinates"]], "Mercator"][[1]]
}
]
Graphics[
{
{FaceForm[], EdgeForm[Black],
Polygon[Map[GeoGridPosition[GeoPosition[#], "Mercator"][[1]] &,
CountryData["Netherlands", "Coordinates"], {2}]]},
Red, PointSize[0.02],
Point@GeoGridPosition[
GeoPosition[
CityData[{"Amsterdam", "NoordHolland", "Netherlands"},
"Coordinates"]], "Mercator"][[1]]
}
]
Cheers -- Sjoerd