Imperial Area Calculations

[CrokinoleMaster]

Hi, Just wanted to let you know that the Imperial area calculations are off by quite a bit. Around 30%

[jacobtoye]

The conversion from metric to imperial can be seen here: https://github.com/Leaflet/Leaflet.draw/blob/master/src/ext/GeometryUtil.js#L32

The method for calculating an area on a sphere is based off here: http://trs-new.jpl.nasa.gov/dspace/handle/2014/40409

Could you give some example of where the actual area is out by 30%?

[CrokinoleMaster]

It's the number of acres that is off. I've just been using metric, getting the hectares then converting to acres. I'll take some screenshots when I have time!

[CrokinoleMaster]

I have an example field that is suppose to be ~160 acres. The default code calculates it incorrectly

incorrect

But doing this then makes it correct since the metric area appears to be good.

            // area *= 0.836127; // Square yards in 1 meter
            //
            // if (area >= 3097600) { //3097600 square yards in 1 square mile
            //  areaStr = (area / 3097600).toFixed(2) + ' mi²';
            // } else if (area >= 4840) {//48040 square yards in 1 acre
            //  areaStr = (area / 4840).toFixed(2) + ' acres';
            // } else {
            //  areaStr = Math.ceil(area) + ' yd²';
            // }
                areaStr = (area * 0.0001 * 2.47105).toFixed(2) + ' acres';

[CrokinoleMaster]

well that was easy! Thanks!

[jacobtoye]

Awesome stuff @huaruiwu! Silly bug from me :( I was converting from metres to yards incorrectly.

[CrokinoleMaster]

no problem. Thanks for all the leaflet work. It's great!