I Find This Hard To Believe

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Posted

Earlier I wanted to confirm how far I am from my old town in England so I go on the net and do a check. Well I was shocked and I am not too sure if the info I got is true or if it is flying miles. What tweaked my interest was the fact  the net said that (on 2 websites) that Paris is 5/6 miles further away than London.Looking at a map I cannot see this so has anybody an explanation?This info is in  miles from Cebu.

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Posted

Its the curvature of the earth.  It plays interesting tricks when you look at flight lines instead of straight lines on a flat map.

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Posted

Its the curvature of the earth.  It plays interesting tricks when you look at flight lines instead of straight lines on a flat map.

I`m not sure what way they are measuring,yes I have a flat map on the wall.

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Posted

Earlier I wanted to confirm how far I am from my old town in England so I go on the net and do a check. Well I was shocked and I am not too sure if the info I got is true or if it is flying miles. What tweaked my interest was the fact  the net said that (on 2 websites) that Paris is 5/6 miles further away than London.Looking at a map I cannot see this so has anybody an explanation?This info is in  miles from Cebu.

In the past I have measured the distance between Central Luzon and Los Angeles California. I used Google earth and found it to be pretty good. Perhaps using that program, you can find the real difference. I assume it would be Straight line distance.

 

 

 

Regards

 

Nephi

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Posted

Things were a lot less complicated when the earth was flat. :th_unfair:

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Posted
so has anybody an explanation?

 

To high of a San Miguel intake? :hystery:

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Posted

It's all to do with Rhumb Lines and Great Circles. The GC distance will be the shorter unless both the GC and RL coincide. That will only happen between two points on the equator or two points on the same meridian of longitude.

A brief explanation is here: http://www.nordian.net/REPOSITORY/110_easa_general_navigation_demo.pdf

Ken

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Posted
A brief explanation is here:

 

Yeh right! I fell into a black hole before I got to the end.

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Posted

Things were a lot less complicated when the earth was flat. :th_unfair:

 

Are you telling me it's not?   :o

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Posted (edited)
t's all to do with Rhumb Lines and Great Circles.

 

That triggered a memory of a program that I wrote several years back for a trucking company.  Part of the program used the GPS position of trucks sent via satellite to find the truck closest to a given customer latitude/longitude.  In case anyone needs  a SQL Stored Procedure to do the same here it is.  No charge for my friends to use this "bad boy" even though it almost caused me to have a brain aneurism by the time I figured it out and got it debugged.  :1 (103):

 

set ANSI_NULLS OFF
set QUOTED_IDENTIFIER OFF
GO
ALTER PROCEDURE [dbo].[Haney_GreatCircleMilesBetweenPoints]
 (
@Latitude1  float,
@Longitude1 float,
@Latitude2  float,
@Longitude2 float,
@Distance float OUTPUT
)
 
-- calc the distance between to lat longs using the great circle formula
-- points are passed either as long int seconds or as decimal degrees
-- example a lat long could be expressed as 47.2531 &  122.2558 OR 170111 &  440121
 
AS
 
-- if lat long is passed in seconds divide by 3600
IF @Latitude1 > 360
BEGIN
   set @Latitude1 = @Latitude1/3600
END
IF @Longitude1 > 360
BEGIN
   set @Longitude1 = @Longitude1/3600
END
 
IF @Latitude2 > 360
BEGIN
   set @Latitude2 = @Latitude2/3600
END
IF @Longitude2 > 360
BEGIN
   set @Longitude2 = @Longitude2/3600
END
 
declare @radius float
 
declare @lon1  float
declare @lon2  float
declare @lat1  float
declare @lat2  float
 
declare @a float
 
-- Sets average radius of Earth in Miles
set @radius = 3956.0E
 
-- Convert degrees to radians
set @lon1 = radians( @Longitude1 )
set @lon2 = radians( @Longitude2 )
set @lat1 = radians( @Latitude1 )
set @lat2 = radians( @Latitude2 )
 
set @a = sqrt(square(sin((@lat2-@lat1)/2.0E)) + 
(cos(@lat1) * cos(@lat2) * square(sin((@lon2-@lon1)/2.0E))) )
 
set @distance =
@radius * ( 2.0E *asin(case when 1.0E < @a then 1.0E else @a end ))
Edited by Mike J
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