static scaleData (source, { coords: { z }, min }) {
        let units_per_meter = Geo.unitsPerMeter(z);
        for (var t in source.layers) {
            var num_features = source.layers[t].features.length;
            for (var f=0; f < num_features; f++) {
                var feature = source.layers[t].features[f];
                Geo.transformGeometry(feature.geometry, coord => {
                    coord[0] = (coord[0] - min.x) * units_per_meter;
                    coord[1] = (coord[1] - min.y) * units_per_meter * -1; // flip coords positive
                });
            }
        }
    }
Re-scale geometries within each source to internal tile units