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Turfjs
Turf buffer buffer distance slightly off
Buffering points creates circles with the required radius, but buffering polygons seems to create buffers with a wrong radius. Here's an example on a very small polygon, buffered with radius 1 miles:
Radius of @turf/buffer output is to small
Buffer with correct radius
Inner object made with @turf/buffer, outer object made with this old PR of turf-buffer (but same can be made using @turf/destination).
I used this data as input.
Not sure what this is due to..
Judging from the initial picture in #786, it seems like this might be related to that issue..
Definitely looks like there's a bug somewhere... looks like it might be the reprojection.
I'm running into the same issue:
let p1 = point([-0.12, 51.2])
let p2 = point([-0.13, 51.8])
let l1 = lineString([[-0.12, 51.2], [-0.13, 51.8]])
let d1 = lineDistance(l1, 'kilometers')
console.log('distance 1: ' + d1)
// distance 1: 66.74149167617327
let b = buffer(p1, d1, 'kilometers')
let e1 = envelope(b)
let l2 = lineString([e1.geometry.coordinates[0][0], e1.geometry.coordinates[0][1]])
let d2 = lineDistance(l2, 'kilometers')
console.log('distance 2: ' + d2 / 2)
// distance 2: 58.858493793982554
let c = circle(p1, d1, 64, 'kilometers')
let e2 = envelope(c)
let l3 = lineString([e2.geometry.coordinates[0][0], e2.geometry.coordinates[0][1]])
let d3 = lineDistance(l3, 'kilometers')
console.log('distance horizontal 3: ' + d3 / 2)
// distance horizontal 3: 67.60143597789236
let l4 = lineString([e2.geometry.coordinates[0][1], e2.geometry.coordinates[0][2]])
let d4 = lineDistance(l4, 'kilometers')
console.log('distance vertical 3: ' + d4 / 2)
// distance vertical 3: 66.74149167617331
EDIT: Corrected variable reference for e2 from b to c -> circles appear good for vertical measurements but off for horizontal measurements per @stebogit comment
@shongololo it seems actually that d2 and d3 are equals in your example because e1 and e2 are both "enveloping" b.
@turf/circle doesn't seem to have issues.
Also, you might want to measure the vertical side of the envelop (lineString([e2.geometry.coordinates[0][1], e2.geometry.coordinates[0][2]])) to compare with the vertical radius of the circle (lineString([[-0.12, 51.2], [-0.13, 51.8]])), because the projection does cause some small difference (see #684).
@stebogit thanks, corrected the typo, circles now are good for vertical though still off for horizontal distances per discussion #684 in your comment.
@DenisCarriere package.json version is 3.14.3
I'll try updating to the latest version
This looks suspiciously like a duplicate of #1470. Closing given it's age and similarities. If still an issue on later versions of Turf please reopen.
