How do I calculate straight line distance on a sphere?

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    Spherical Trigonometry
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Discussion Overview

The discussion revolves around calculating the straight line distance between two points on a sphere, contrasting it with the great circle distance. Participants explore the implications of different types of distances, including the concept of straight lines in relation to the sphere's surface.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant seeks guidance on calculating straight line distance on a sphere, noting they have already found great circle and parallel distances.
  • Another participant asserts that great circles (or geodesics) represent the shortest distance between two points on a sphere, suggesting they are the generalized concept of a 'straight line'.
  • A participant questions whether the 'straight line' refers to a line passing through the sphere rather than along its surface.
  • One suggestion is made to convert the coordinates to Cartesian form to apply the distance formula for calculating the straight line distance.

Areas of Agreement / Disagreement

Participants express differing interpretations of what constitutes a 'straight line' in the context of a sphere, leading to uncertainty about whether this distance is equivalent to the great circle distance. The discussion remains unresolved regarding the definitions and calculations involved.

Contextual Notes

The discussion highlights potential ambiguities in definitions of distance on a sphere, particularly between surface distances and those through the sphere. There are also references to specific assignments and handouts that may influence the understanding of the problem.

G4CKT
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Hi everyone,

I've tried googling how to calculate a straight line distance on a sphere. I got no answers for it though T_T.

I was able to find the great circle distance and parallel's already.

I'm given 2x points with lats/longs and ellipsoidal heights.

Can anyone guide me in the right direction?
 
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the great circles (or "geodesics") are the answer; they are the shortest distance between two points on a sphere (and therefore they are the generalized concept of a 'straight line').
 
zhermes said:
the great circles (or "geodesics") are the answer; they are the shortest distance between two points on a sphere (and therefore they are the generalized concept of a 'straight line').

In my assignment I was asked to find. The 2x parallel distances (I did), great circle distance (I did, and this "Straight Line" distance. Would that straight line distance be equivalent to the great circle distance? In the handout I received he drew the great circle distance and beside it he drew a straight line distance xD
 
is the 'straight line' actually a straight line? (i.e. it is NOT on the surface of the sphere, but passing through it?)
 
zhermes said:
is the 'straight line' actually a straight line? (i.e. it is NOT on the surface of the sphere, but passing through it?)

Here is the image

[PLAIN]http://img442.imageshack.us/img442/8727/spheren.png
 
Last edited by a moderator:
Ah gotcha, an actual straight line. Your best bet is probably to convert to Cartesian coordinates and just use the distance formula.
 
zhermes said:
Ah gotcha, an actual straight line. Your best bet is probably to convert to Cartesian coordinates and just use the distance formula.

Ah, okay so that's what it is I totally forgot about conversions.

Thanks for the help!
 

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