Proj4Leaflet
This is an early attempt at integrating Proj4js with the excellent map client Leaflet. We decided to put this into a separate library for now to avoid adding unnecessary dependencies to Leaflet.
Example
Defines the EPSG:2400 (RT90) projection in Proj4 format and returns a Leaflet CRS object which can be used as the "crs" option to L.Map.
// RT90
L.CRS.proj4js('EPSG:2400',
'+lon_0=15.808277777799999 +lat_0=0.0 +k=1.0 +x_0=1500000.0 ' +
'+y_0=0.0 +proj=tmerc +ellps=bessel +units=m ' +
'+towgs84=414.1,41.3,603.1,-0.855,2.141,-7.023,0 +no_defs',
new L.Transformation(1, 0, -1, 0));
// ETRS89 / UTM zone 33N
L.CRS.proj4js('EPSG:25833',
'+proj=utm +zone=33 +ellps=GRS80 +units=m +no_defs',
new L.Transformation(1, 2500000, -1, 9045984));
// SWEREF 99 TM
L.CRS.proj4js('EPSG:3006',
'+proj=utm +zone=33 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs',
new L.Transformation(1, -218128.7031, -1, 6126002.9379));More details in examples/script.js
Transformations
Transformation turns projected coordinates into pixel coordinates corresponding to a given zoom.
It uses the following formula:
point.x = scale * (this._a * point.x + this._b);
point.y = scale * (this._c * point.y + this._d); which we usually define as
a = 1
b = -(x_origin)
c = -1
d = y_origin
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