MGLMapCamera misinterprets eye coordinate

[1ec5]

+[MGLMapCamera cameraLookingAtCenterCoordinate:fromEyeCoordinate:eyeAltitude:] calculates a pitch in radians and passes it into -initWithCenterCoordinate:altitude:pitch:heading:, which expects the pitch in degrees, so the resulting MGLMapCamera has much less of a pitch than expected, the wrong heading, and a shorter viewing distance – so the eyeCoordinate parameter doesn’t have the intended effect. If the tangent happened to be negative, then MGLMapView would ignore the pitch altogether.

mapbox-gl-native/platform/darwin/src/MGLMapCamera.mm

Lines 35 to 36 in 66e95ac

	heading = std::atan((centerMeters.northing() - eyeMeters.northing()) /
	(centerMeters.easting() - eyeMeters.easting()));

mapbox-gl-native/platform/darwin/src/MGLMapCamera.mm

Line 40 in 66e95ac

pitch = std::atan(eyeAltitude / groundDistance);

This significant discrepancy has apparently always been present in the MGLMapCamera implementation, since #2193. Unlike #12943, I think it would be tenable to fix the bug in-place, because the developer’s intent by using this method is pretty clear.

/cc @mapbox/maps-ios @d-prukop

[1ec5]

If you pass the same coordinate twice into +[MGLMapCamera cameraLookingAtCenterCoordinate:fromEyeCoordinate:eyeAltitude:], the resulting camera incorrectly has a pitch of about 1.5° (a right angle in radians, but interpreted as degrees) instead of 0° and a heading of NaN instead of 0°.