East-West error at regular points on the Azimuthal Equidistant Map

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Discussion Overview

The discussion revolves around the east-west distance errors on the Azimuthal Equidistant map projection, particularly as it relates to distances measured at various latitudes from the North Pole to the South Pole. Participants explore the nature of these errors and seek to quantify them through graphical representation and mathematical calculations.

Discussion Character

  • Exploratory
  • Mathematical reasoning

Main Points Raised

  • One participant notes that the Azimuthal Equidistant map is accurate for north-south distances along lines of longitude but that east-west distance errors increase significantly as one moves away from the North Pole.
  • The same participant requests a method to graph the east-west distance errors at various latitudes, specifically at 60N, 45N, 30N, the Equator, 30S, 45S, and 60S, suggesting that the errors may be exponential.
  • Another participant responds with a mathematical approach, providing a formula for calculating the circumference of circles of latitude based on a sphere with a circumference of 1 at the equator.
  • A follow-up question is posed regarding the circumference at 15 degrees north, to which a participant provides a calculated value using the cosine function.

Areas of Agreement / Disagreement

Participants appear to agree on the nature of the east-west distance errors increasing with latitude, but the discussion remains open regarding the specific quantification of these errors and the best methods to represent them graphically.

Contextual Notes

The discussion does not resolve the exact nature of the error calculations or the graphical representation methods, leaving these aspects open for further exploration.

Miles Behind
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TL;DR
HELP ME get east west error for circles of latitude on the Azimuthal Equidistant projection as compared to the Globe.
Hello. I am conversing with Flat-Earth folks who tend to lean upon the Azimuthal Equidistant (AE) map centered on the North pole. I know that the AE map is a projection of the globe onto a flat surface, and is only accurate in distances north and south along lines of longitude. The east west distance error increases every mile away from the north pole, approaching silly amounts near the equator and Antarctic latitudes, and quickly increasing to infinity at the south pole. Can someone give me something that I can graph out on paper showing the (I suspect are exponential) error of east-west distances at multiple points between the north and south poles along circles of latitude? Perhaps give the distortion errors at 60N, 45N, 30N, Equator, 30S, 45S and 60 degrees south as a minimum (of course the east-west map error would be zero at the north pole, and infinite at the south pole). What measured distance error would be found for a short distance east and west at these points? Say along a 1 degree section? Is there a better way to do it?

Also. For a sphere with a circumference of 1 at its equator, what would be the circumference of the 30 degree, 45 degree, 60 degree north circles of latitude?
 
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Miles Behind said:
... Also. For a sphere with a circumference of 1 at its equator, what would be the circumference of the 30 degree, 45 degree, 60 degree north circles of latitude?
Earth circunferences.jpg
 
Excellent! Thank you much! By the way, what would the value be for 15 degrees north?
 
You are welcome.
For 15 degrees north the value would be simply 1.0 x cos (15) = 0.9659.
 

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