Mapwize Georeference for JavaScript

Library to work with georeference and project and unproject points between x/y and latitude/longitude WGS84 coordinates.

Georeference

A georeference is an array of at least 2 objects with format like

{
    "points": [
        {
            "x": 1310.2132295719841,
            "y": 1406.1883268482486,
            "latitude": 50.63264941120241,
            "longitude": 3.0202874193832945
        },
        {
            "x": 0,
            "y": 0,
            "latitude": 50.63261391508114,
            "longitude": 3.0206033053400465
        }
    ]
}

where x and y are the coordinates of a point in the local coordinate system and latitude and longitude are the world coordinates of the same point.

This library expects the x/y coordinates system to be orthonormal! This means:

• The x axis is horizontal, increasing to the right
• The y axis is vertical, increasing to the top
• One unit on the x and y axis correspond to the same distance in the phycical world

Please note that for pixels in images, the y axis is often pointing downwards. You need to count the pixels from the bottom-left of the image for this library to work.

Projections

Methods are available to project coordnates and GeoJSON features from x/y to latitude/longitude coordinates and vice-versa.

projectPointForGeoreference = function(point, georeference) 
projectFeatureForGeoreference = function(feature, georeference)
unprojectLatLngForGeoreference = function(latLng, georeference)
unprojectFeatureForGeoreference = function(feature, georeference)

point and latLng are an array of 2 numbers like [0, 0].

feature is a GeoJSON feature.

Tests

Some tests are available in the tests directory and give some details on how to use the library.

You can run them using:

npm run test