Lambert 72 not always correctly shown? #12
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Thanks, I'll look into this! I checked in QGIS against the same base map and it looks fine there:
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A quick update on this. It looks like the provided data use a different transform for EPSG:31370 from the epsg.io default. https://epsg.io/31370 lists 4 possible transforms, and more are available in the database. Here's a comparison of some of the available transformations as well as links to the app to show the resulting position shifts:
const proj = require("proj4");
const ll = [3.533646, 50.981898];
const transforms = [
"+proj=lcc +lat_0=90 +lon_0=4.36748666666667 +lat_1=51.1666672333333 +lat_2=49.8333339 +x_0=150000.013 +y_0=5400088.438 +ellps=intl +towgs84=-106.8686,52.2978,-103.7239,-0.3366,0.457,-1.8422,-1.2747 +units=m +no_defs +type=crs",
"+proj=lcc +lat_0=90 +lon_0=4.36748666666667 +lat_1=51.1666672333333 +lat_2=49.8333339 +x_0=150000.013 +y_0=5400088.438 +ellps=intl +towgs84=-99.059,53.322,-112.486,-0.419,0.83,-1.885,-1 +units=m +no_defs +type=crs",
"+proj=lcc +lat_0=90 +lon_0=4.36748666666667 +lat_1=51.1666672333333 +lat_2=49.8333339 +x_0=150000.013 +y_0=5400088.438 +ellps=intl +towgs84=-125.8,79.9,-100.5,0,0,0,0 +units=m +no_defs +type=crs"
];
for (tr of transforms) {
transform = proj(tr);
const xy = transform.forward(ll);
console.log(xy);
console.log(transform.inverse(xy));
console.log("POINT(" + xy[0] + " " + xy[1] + ")");
}I'll look into options for switching between transforms. Related: maptiler/epsg.io#171 |
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For example, this Lambert72 is slightly shifted
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