CODEWITHSUNDEEP
javascriptprojectionmercator
r123454321
r123454321

Reputation: 3403

Convert to and from lat/lng and pixels in web mercator at arbitrary floating point zoom levels?

I'm using the following npm module to convert to/from lat/lng and pixels:

https://www.npmjs.com/package/viewport-mercator-project

Here's the usage:

// Create a new viewport. 
var ViewportMercator = require('viewport-mercator-project');
// NOTE: `ViewportMercator` objects are immutable by design. 
var viewport = ViewportMercator({
  center: [0, 0],
  zoom: 0,
  tileSize: 512,
  dimensions: [600, 800]
});

var lnglat = [0, 0];
var pixels = viewport.project(lnglat); // returns [300, 400] 

viewport.unproject(pixels); // returns [0, 0]

However, this always seems to fail in my use case, where my center is -122~:

ViewportMercator({
      center: [37.7833, -122.4167],
      zoom: 13,
      tileSize: 512,
      dimensions: [1000, 778]
    });
> viewport.project([37.7833, -122.4167])
[ 500, NaN ] // should return (500, 389)

I know this has something to do with the fact that my lng value (in the center) is outside of the range -90 < lng < 90, but how can I fix this? My attempted viewport conversion is definitely valid...

Upvotes: 1

Views: 1062

Answers (1)

ghybs
ghybs

Reputation: 53205

It seems to me that you just interverted the longitude and latitude.

ViewportMercator expects an array of the form [longitude, latitude] in center and as argument of project.

The point at longitude -122.4167 and latitude 37.7833 is in San Francisco.

http://www.openstreetmap.org/search?query=37.7833%2C%20-122.4167#map=10/37.7833/-122.4167

Upvotes: 1

Related Questions