Latitude and Longitude - has anyone done the maths?

[JohnGray]

I wonder whether anyone has worked out the difference in metres in the 5th decimal place of the usual figures for latitude and longitude in the UK.

For example, in the Motorway Junctions POIs, the values of
Longitude vary from about -4.54824° (West) to 1.15972° East
and the values of
Latitude vary from about 50.68351° to 56.38705° (North).

How much distance on the ground, roughly, does a change of 1 in the fifth decimal place represent for each direction (north-south and east-west)?

Taking the mid-point of the motorway system,
what's the distance between -1.69426° W and -1.69427° W Longitude
and between 53.53528° N and 53.53529° N Latitude?

And a supplementary question on these PGPSW POI files themselves: there are two files, one for Motorway Junction Entries and one for Motorway Junction Exits. Both use the same naming convention. Would it be necessary to suffix each row with "entry" or "exit", as appropriate, if the files were to be combined and uploaded to a Garmin Nuvi, so that they could be distinguished?

Thanks!

[Skippy]

[M8TJT]

And multiply it by the cosine of your lattitude to find the distance E/W. So 0.00001 =about 3.3 feet N/S (skippy's calculation) and about 2.1 feet E/W at lat 50

[Oldboy]

[Andy_P]

[Daggers]

[Andy_P]

Of couse... silly me.
Ignore that bit of my last post!
_________________
"Settling in nicely" ;-)

[M8TJT]

[Andy_P]

I said "i would go...."

But all right, just for you.

{time passes}

Yeah ok.... It's a bit too close to see, isn't it? Even on maximum zoom!

How about changing the THIRD decimal by one and dividing the distance on the ground by 100? Or doesn't it work like that?

{time passes}

That seems to give the right sort of result...



So 1.11 metres for 0.00001 deg of latitude in southern UK?
_________________
"Settling in nicely" ;-)

[JohnGray]

Thanks for everyone's answers!

I have done some deep research (using Wikipedia's article on latitude and longitude!) and calculate
* for all longitudes (W-E), the latitude length(N-S) is 1.106 metres for each change of 0.00001° in latitude position
* for the most southerly latitude 50.68351°, the longitude length(W-E) is 0.705 metres for each change of 0.00001° in longitude position
* for the most northerly latitude 56.38705°, the longitude length(W-E) is 0.616 metres for each change of 0.00001° in longitude position

('most southerly' and 'most northerly' relate to the latitudes of the junctions found in the Motorway Junctions POI file)

Precision will depend minimally on the heights above sea level, and so on.

I do hope that this is correct!

[M8TJT]

A good way to work things out is to know that 1 degree of lattitude is 60 nautical miles (NM) (originally by definition). A NM is 1.85200 Km or if you prefer old money it's approximately 6,076 feet. It all becomes easy now. 1 degree = 6076 * 60 = 364,560ft. So the answer to the question is 364,560ft * 0.00001 = 3.64560ft. As I said before, multiply the distance N/S by the cosine of the latitude to give the distance E/W So a more accurate calculation of 0.00001 deg E/W at 50N is 2.34334651ft.

[Skippy]

[M8TJT]

[Andy_P]

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