Kilometers on the tube. What is the decimal distance?

[heart-of-wessex]

Hello all,

I'm looking in the Quail map for the Underground and I'm confused at the distances used for the measurements. It states that it is in Kilometers but what is the decimal distance. For instance, there is kilometer points like 50.18...what is the .18 measured in? I thought it might have meant 50km.18ch, but it can't be chains as there are distances of over .80 (like .91).

I then thought maybe meters like 50km.18m but the distance between stations is very short than it should be. There is one in the Quail that is 50.18 to 50.71, and also in brackets of that distance is 8m 48ch to 8m 77ch...a total of 583 meters. But it is the only distance in that section that shows the mileage so I can't work out the rest!

I thought it might be yards, so I converted the distance (.18 to .71 is .53) from 0.53km to yards and then converted yards back into meters. Answer 533m...not 583m...
I am very confused to how I should calculate this to get the answer in meters! The Quail doesn't state what the .xx is in, just says it's Kilometers otherwise miles and chains where stated.

Does anyone know what unit of measurement it is so I can convert it into meters please?


Kind Regards,

James.

 

[Eagle]

Erm... what? It's just an ordinary decimal number.

50.18 means fifty point one eight kilometers. Simple as.

0.01 km is ten metres, but I'm sure you knew that already.

 

[bb21]

Erm... what? It's just an ordinary decimal number.

50.18 means fifty point one eight kilometers. Simple as.

0.01 km is ten metres, but I'm sure you knew that already.

I think what he meant is that using the miles-chains measurement, the distance is 29 chains, equating to 583 metres.

However using the kilometres measurement, the distance over the same stretch comes out at 530 metres.

Measurements between yards and meters are only roughly 10% apart so it would not have made any difference.

This means that there is a discrepancy.

 

[Eagle]

Hmm. Those numbers seem to be the kilometrages of Stamford Brook and Turnham Green on the District/Piccadilly line... so why specifically that bit would have a distance in miles.

However this bit of tube line (Hammersmith to Richmond specifically) started off as a branch of the WLL built by the LSWR, so maybe the mileage is from that—it does look right for the distance to Waterloo via Kensington Olympia.

I suggest that the measurements were made at different times, many years apart: the mainline miles one in the later 19th century and the tube km one in the later 20th, and they won't have been measured from the same points, so a 50 m discrepancy is easily possible (and that's assuming the platforms haven't been moved in the intervening 100 years!).

 

[heart-of-wessex]

bb21 - yes thats right I have two answers for one distance.

Eagle - I didnt actually know that, but thank you. I didnt do well at maths at all!
Yes the distance in miles is measured from waterloo, but it not given at all locations. Either case 500m sounds right either case, my yards distance for West Kensington - Earls Court seemed too long at 800m

 

[MidnightFlyer]

Doesn't Quail give MCh on relevant NR / LUL shared sections. Either way, RailMiles give imperial LUL mileages.

Quail also states at some point on the diagrams origins of mileages.

 

[Eagle]

I've looked into it further and the mileages given for your bit of the tube, when extrapolated, match up perfectly with the ones from Gunnersbury to Richmond on the NLL (which would have been the end of the LSWR line).