Update distance measurement factors

[dhivehi]

Turf line distance calculation is not accurate according to google earth. Is there any way to use custom radius in calculation?

[DenisCarriere]

Please provide more context for you issue.

@turf/distance is using the Haversine formula which takes into consideration the curvature of the earth.

Closing this issue.

[dhivehi]

its not the formula issue, but the problem is the earth radius being used is not the radius used in google earth.

[dhivehi]

Official google earth's radius is 6378137meters.
I'm guessing this code is the problem.

var r={miles:3960,nauticalmiles:3441.145,degrees:57.2957795,radians:1,inches:250905600,yards:6969600,meters:6373e3,metres:6373e3,kilometers:6373,kilometres:6373,feet:20908792.65}

[DenisCarriere]

👍 Agreed

You could send a PR with a fix for https://github.com/Turfjs/turf/blob/master/packages/turf-helpers/index.js#L264-L276

[dhivehi]

I have send a PR, but it failed for some reason. I donno why. I'm new to github PR. This was my 1st PR in github.

[dpmcmlxxvi]

My guess would be that, since the helper functions are used everywhere, changing their numerical behavior has affected unit tests throughout the entire library. One of the errors on travis-ci is an expected output not matching a fixture. Changing these constants will probably require going through and addressing all downstream unit tests that depend on the helper functions that rely on these constants.

[dhivehi]

So could you suggest a fix or can u fix it?

[dpmcmlxxvi]

I suggest you look at the travis-ci report and inspect at each unit test error returned in your PR. The error tells you what was the expected value and what was the actual value. Track down the cause of the difference and you'll likely see that some distance calculation is the root cause. Then update those tests.

[DenisCarriere]

@dpmcmlxxvi Exactly.

@dhivehi I pushed a commit to your PR b7e826a which should of updated the the libraries that depend on @turf/helpers & @turf/distance.

The only things that really changed was the factors from your commits a65c237.

var factors = {
    miles: 3963.190592,
    nauticalmiles: 3443.918467,
    degrees: 57.2957795,
    radians: 1,
    inches: 251107755.9055118,
    yards: 6975215.442,
    meters: 6378137,
    metres: 6378137,
    kilometers: 6378.137,
    kilometres: 6378.137,
    feet: 20925646.325459316
};

CC: @tmcw @morganherlocker

[dhivehi]

So does this means now the issue is fixed?

[DenisCarriere]

It will be fixed in the next minor/patch release, just waiting for a response from @tmcw or @morganherlocker (if it's OK with them I can submit the release).

The @turf/distance & @turf/helpers affect many modules outside of Turf, I don't want to release this yet until I've got the 👍 from someone else.