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Zero point for mileage on the Ungerground.

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Chris Butler

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The Wikipedia article for Ongar station says that "the eastern buffers remain the point from which all distances on the London Underground are measured.". Some posts on here also say the same, but give no other information.

Is it true ? If so, how does the mileage (or kilometerage) on lines other than the Central get calculated ?
 
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Harsig

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Ongar is still the origin of all lines except Waterloo & City. The 'mileage' transfers to other lines either at physical junctions or in some cases parallel platforms, counting forwards or backwards as appropriate to the direction. See http://www.railwaycodes.org.uk/track/distances/undergrounddistances.pdf amongst other places to see how the mileage count works.

To expand on that a little. The purpose of the 'kilometerage' is to allow for easy identification of specific locations on any given line. It is not there to tell you how far you are from Ongar, and in most cases this won't tell you. As long as the distance given is relatively unique in the general area, it serves its purpose regardless of what that actual measurement is.
The Underground could have adopted an origin point for each individual line, but this would have led to different measurement on sections where two lines run parallel.

The first transfer point for distance measurements is Mile End. At this point the distance on the Central Line from Ongar is 33.1KM (and continues to increase the further west you go). The District Line at this point is arbitrarily defined as also having a distance of 33.1KM, and the distance measurement on the District increases from this value as you travel west. Crucially as you travel east from Mile End on the District the distance measurement on this line decreases from 33.1KM, dropping to 12KM at Upminster.

The transfer points between lines are:
Mile End: Central to District Line 33.1KM
Barons Court: District to Piccadilly Line 47.84KM
Rayners Lane: Piccadilly to Metropolitan Line 64.3KM
Finsbury Park: Piccadilly to Victoria Line 34.3KM (counted down from Barons Court)
Kings Cross: Piccadilly to Northern Line 38.4KM (counted down from Barons Court)
Finchley Road: Metropolitan to Jubilee Line 50.1KM (counted down from Rayners Lane)
Baker Street: Jubilee to Bakerloo Line 46.6 (counted down from Finchley Road)
The Hammersmith & City & northern side of the Circle lines are treated as part of the Metropolitan line, but there is an abrupt change in the distance measurements where these lines meet the District Line.

Since distance measurements both decrease and increase from a transfer point it was necessary to select an origin point sufficiently far from any transfer point so as to ensure that any decreasing distance measurement on the other line(s) never reached zero. Ongar was chosen. The only other likely candidate was probably Chesham, although this was probably ruled out as the count-back from Chalfont towards Amersham and the BR/LU boundary would have got very close to zero.

It will be seen from the above that the only sections of line whose distance measurements actually tell you how far you are from Ongar are:
Central Line (excluding the Hainault loop)
District Line west of Mile End (except Earls Court to Edgware Road)
Piccadilly Line west of Barons Court
Metropolitan Line Rayners Lane to Uxbridge only.
 

Chris Butler

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To expand on that a little. The purpose ...

Thanks for that. I really apprecited it.

At first glance the system does have the look of an April Fool that got taken too literally. As you say physical distance is not relevant. For example, Morden Depot is 'closer' to Ongar than Woodford, for the reason you gave. More subtly, Stratford is 'closer' to Ongar on the Jubilee, despite being routed via Mile End and Finchley Rd, than the direct journey on the Central.

The thing that still puzzles me is that the objective of ensuring that "the distance given is relatively unique in the general area," isn't really met. By their very nature transfer points are surrounded by locations with identical kilometerages and which are in close proximity, but on different lines. I'm still hoping to discover that the whole thing was dreampt up late at night in the Two Chairmen, just round the corner from 55 Broadway :lol:

I read that the 0.0 post is still in-situ at Ongar. I hope that is true.

By the way, the transfer points are underlined on that wonderful map that pdeaves so kindly supplied.
 

Hadders

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This post on Diamond Geezer is worth a read

https://diamondgeezer.blogspot.com/2018/07/look-back-from-ongar.html

Last weekend I went to the Epping Ongar Railway, and rode some trains and buses, and walked to an old church, and came away with a real ale festival tankard for my trouble.

I've written about the Epping Ongar Railway before, so I won't do so again. But while I was there I did pay extra-special attention to this sign beside the buffers at Ongar station.



It marks the zero point on the Underground, from which all official distances are measured (even though the Underground hasn't actually served Ongar since 30th September 1994).

Distances are measured in kilometres from Ongar.
Epping is 9.85km away. Buckhurst Hill is 19.61km away. Stratford is 30.30km away. And so on.

Here's my "and so on" list for the Central line, pausing approximately every 10km from Ongar.
Central (measured from Ongar=0)
0 Ongar, 10 Epping, 20 Buckhurst Hill, 30 Stratford, 40 Holborn, 50 East Acton, 60 NortholtOn other lines, distances are measured from a known point on a line already measured. A station is picked where the tracks run parallel, and measurement then extends in either direction, forwards or backwards.

For example, the 'transfer' point for the District line is Mile End station (where the District runs in parallel to the Central line). Mile End is 33.07km from Ongar, so all distances on the District line are measured up and down from Mile End.
District (measured from Mile End=33)
20 Dagenham Heathway, 30 West Ham, [ME], 40 Embankment, 50 Stamford Brook/Putney BridgeThe transfer point for the Piccadilly line is Barons Court (where the Piccadilly runs in parallel to the District).
Piccadilly (measured from Barons Court=48)
30 Wood Green, 40 Holborn, [BC], 60 Hounslow East/Sudbury Town, 70 Heathrow T5/IckenhamThe transfer point for the Victoria line is Finsbury Park (where the Victoria runs in parallel to the Piccadilly).
Victoria (measured from Finsbury Park=34)
30 Tottenham Hale, [FP], 40 Warren Street, 50 BrixtonThe transfer point for the Northern line is just outside King's Cross (on the so-called King's Cross Loop, a tunnel which connects to the Piccadilly).
Northern (measured from King's Cross=38)
30 Clapham Common/Battersea Power Station, [KX], 40 Mornington Crescent, 50 Hendon Central/Finchley CentralThe transfer point for the Metropolitan line is Rayners Lane (where the Metropolitan meets the Piccadilly).
Metropolitan (measured from Rayners Lane=64)
40 Aldgate, 50 Finchley Road, 60 Northwick Park, [RL], 70 Ickenham/Northwood, 80 Chalfont & LatimerThe transfer point for the Circle line is Baker Street (where the Circle diverges from the Metropolitan).
Circle (measured from Baker Street=47)
40 Aldgate, [BS], 50 Ladbroke Grove/Notting Hill GateThe transfer point for the Jubilee line is Finchley Road (where the Jubilee runs in parallel to the Metropolitan).
Jubilee (measured from Finchley Road=50)
30 Canning Town, 40 London Bridge, 50 Finchley Road [FR], 60 KingsburyAnd finally the transfer point for the Bakerloo line is Baker Street (where the Bakerloo runs in parallel to the Jubilee).
Bakerloo (measured from Baker Street=47)
40 Elephant & Castle, [BS], 50 Maida Vale, 60 North WembleyTo run that backwards, the official distance for North Wembley is 59.86km, measured back to the Jubilee line at Baker Street, measured back to the Metropolitan line at Finchley Road, measured back to the Piccadilly line at Rayners Lane, measured back to the District line at Barons Court, measured back to the Central line at Mile End, measured back to a set of buffers at Ongar that's no longer on the Underground.

It's mad, but it's brilliant... or at least it is if I've understood what's going on properly. I unravelled all this from the excellent Clive's UndergrounD Line Guides, which I've been quoting on this blog ever since it began. It has an utterly invaluable page of data for every Underground line, and an introductory page detailing how all the data is measured. Thanks Clive!

And if you'd like a map with all the distances on, because I suspect you probably would, here's one (courtesy of the website railwaycodes.org.uk, which I suspect is a timesink of infrastructure geekery on another level completely).
 

edwin_m

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The thing that still puzzles me is that the objective of ensuring that "the distance given is relatively unique in the general area," isn't really met. By their very nature transfer points are surrounded by locations with identical kilometerages and which are in close proximity, but on different lines. I'm still hoping to discover that the whole thing was dreampt up late at night in the Two Chairmen, just round the corner from 55 Broadway :lol:
This is true. To identify a unique location on the Underground you have to quote the line as well as the kilometreage. And where the lines themselves have junctions, you need to quote the relevant branch. Network Rail has a code called Engineer's Line Reference which ensures that any location can be identified by quoting the ELR and miles from whatever zero point applies. I found the page linked below with an incomplete list of an equivalent system for LU, but I don't know if this is widely used.

http://www.railwaycodes.org.uk/elrs/elr1.shtm
 

DavidGrain

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I did manage one day to get to Ongar shortly before it closed so did see the Zero post. I am not sure if that was the same day that I made my last trip on the Aldwych branch.

The Underground did in the past run on further beyond Amersham but then that was before the use of kilometres and the mileages would have been the old Great Central mileages which have their zero point in Manchester via Sheffield.
 

Chris Butler

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The Underground did in the past run on further beyond Amersham but then that was before the use of kilometres and the mileages would have been the old Great Central mileages which have their zero point in Manchester via Sheffield.

I'm assuming that's why Ongar was chosen. To avoid negative mileage you need an extreme point and, as Harsig mentioned, ideally no nearby branch. Chesham was probably ruled out for these reasons.
 

Chris Butler

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To identify a unique location on the Underground you have to quote the line as well as the kilometreage. And where the lines themselves have junctions, you need to quote the relevant branch.

Exactly. So I can't see what advantage the Ongar-centric approach gives over just choosing a zero at one extreme of each line.

It's more fun though :lol:
 

DavidGrain

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I'm assuming that's why Ongar was chosen. To avoid negative mileage you need an extreme point and, as Harsig mentioned, ideally no nearby branch. Chesham was probably ruled out for these reasons.

Yes some of the platforms at Euston now have the buffers at negative mileages.
 

edwin_m

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Yes some of the platforms at Euston now have the buffers at negative mileages.
This is presumably the Network Rail mileage in the main station, not the LU kilometreage, reflecting the extension of the platforms towards Euston Road in the 1960s. The map linked above shows Euston at km45.68 via the Overground, although as the Overground is NR infrastructure I assume the kilometreages aren't very relevant except perhaps the East London Line.
 

Busaholic

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What would have happened in the unlikely event of the railway being extended beyond Ongar?!
 

edwin_m

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What would have happened in the unlikely event of the railway being extended beyond Ongar?!
The Ongar line along with most of the rest of the eastern end of the Central line was taken over post-war from the LNER and indeed retained freight trains into the 1960s. I think at the time it was understood that further extension was unlikely due to the green belt preventing further development in the area. But if it had been extended before the kilometreages were established then the zero would presumably have been at the new terminus. If extended afterwards, changing the kilometreage would have been an unnecessary cost and confusion as all sorts of drawings and documents make use of them. So they would just have started a new kilometreage for the new extension, possibly ascending from Ongar in the other direction.

This may be a(nother) reason why Ongar was chosen as the zero rather than Chesham or Amersham, as it's possible to imagine several alternative histories where the Met re-extended towards Aylesbury, for example if Marylebone had been closed as proposed in the 80s.

Incidentally if the linked underground distances map was updated to include Crossrail, then assuming the obvious transfer point at Stratford the kilometreage at Shenfield would be well into minus figures.
 

DavidGrain

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Incidentally if the linked underground distances map was updated to include Crossrail, then assuming the obvious transfer point at Stratford the kilometreage at Shenfield would be well into minus figures.

Having time on my hands with the present lockdown I have come back to this thread. Crossrail will be interesting as it is not a London Underground line it will not have mile/kilometres calculated from the Tube line. The parts of the line currently operating will have have mileages zeroing at Paddington going west and Liverpool Street going east so I presume the dedicated part os the Elizabeth Line will follow the normal National Rail policy of zero at one of the junctions either on the Great Western or Great Eastern line counting up towards the other junction.
 

Dstock7080

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On this map, there appear to be turnback loops on the Northern Line at Embankment and Kennington. Is this true?
Kennington survives and Charing Cross was the terminal loop of the Charing Cross, Euston and Hampstead Railway
 

Peter Mugridge

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On this map, there appear to be turnback loops on the Northern Line at Embankment and Kennington. Is this true?

The Kennington loop, yes.

The Embankment loop I am pretty sure has been disused and sealed off for many, many years. I believe it was last used in the 1920s.
 

DavidGrain

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On this map, there appear to be turnback loops on the Northern Line at Embankment and Kennington. Is this true?

On what is now the Charring Cross Branch of the Northern line the original terminus was at the station now know as Embankment where there was a turnround loop. When the line was continued south to Kennington this loop was taken out of service but I believe that the southbound tracks do follow much of the curve separating from the northbound track by some distance under the river resulting in the north and south platform not being parallel to each other in the station.

Most of the Charring Cross trains terminate at Kennington dropping their passengers off at a platform parallel to the southbound platform of the Bank branch then run round the loop to come back to a platform parallel to the north bound Bank branch. The Bank branch trains cannot access this loop and have a turnback siding if they need to terminate at Kennington. A few rush hour trains on the Charring Cross do continue to Morden using crossovers to get to the Bank platforms.

The description above will change when the Battersea extension opens as Battersea trains will be served by Charring Cross trains and the extension lines will come off the loop. You can see how this will work from the map.
 

edwin_m

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Having time on my hands with the present lockdown I have come back to this thread. Crossrail will be interesting as it is not a London Underground line it will not have mile/kilometres calculated from the Tube line. The parts of the line currently operating will have have mileages zeroing at Paddington going west and Liverpool Street going east so I presume the dedicated part os the Elizabeth Line will follow the normal National Rail policy of zero at one of the junctions either on the Great Western or Great Eastern line counting up towards the other junction.
I agree Crossrail and Overground won't have their chainages reference from the Tube. I believe I mentioned it because the site we were discussing back then attempted to do that.

I also agree there will be some kind of new chainage for Crossrail and once it joins the existing route either end there will be a change of chainage just as there are on many other places on Network Rail. The new "chainage" may be in metres as I believe it has been converted on the ERTMS section of the Cambrian, but if any existing chainages are converted to metres they will probably still be from the same zero point, as is commonly seen on signalling plans.
 

DelW

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On what is now the Charring Cross Branch of the Northern line the original terminus was at the station now know as Embankment where there was a turnround loop. When the line was continued south to Kennington this loop was taken out of service but I believe that the southbound tracks do follow much of the curve separating from the northbound track by some distance under the river resulting in the north and south platform not being parallel to each other in the station.
It's slightly different from that - the southbound platform and tunnel are actually straight, and cut across the original loop, but the curvature of the northbound platform is because that is a surviving section of the loop.
 

Mojo

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Nice Map
Not sure I understand the distances quoted for Watford East Junction mind
I guess via North Curve should be 73.80
Watford East Junction is at 73.32km and North Junction at 73.41km.
 

jumble

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Watford East Junction is at 73.32km and North Junction at 73.41km.
Thats no doubt true
I was looking at the bit on the map that suggests it is a shorter distance to East junction via north curve than via south curve which appears to be nonsense
 

Mojo

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Thats no doubt true
I was looking at the bit on the map that suggests it is a shorter distance to East junction via north curve than via south curve which appears to be nonsense
It appears to be data from the Clive's Underground Line Guides website.

I'm _guessing_ the reason his website (and the map linked to above) shows the lower number of kms via the North Curve is because of the difference in distances. Moor Park Station to Croxley Station is 2.94km and Rickmansworth Station to Croxley station is 2.67km. Moor Park Station to Rickmansworth Station is 3.49km. Remember that the system exists to provide a datum / reference point as to a specific location rather than to measure distances. The exact kilometerage of stations is not recorded, but if you go by the numbers he has used (which are slightly wrong) it would give a lower number going via the North Curve as he has presumably counted down from Rickmansworth (or the junction) and up from Moor Park, this would give a lower number from Rickmansworth [74.52 - 2.67 is lower than 71.16 + 2.94]
 

pdeaves

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Thats no doubt true
I was looking at the bit on the map that suggests it is a shorter distance to East junction via north curve than via south curve which appears to be nonsense
Generally speaking, if you reverse direction you count back the other way. So, count up to one junction, then count downwards around the triangle to the other junction.
 

etr221

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Thats no doubt true
I was looking at the bit on the map that suggests it is a shorter distance to East junction via north curve than via south curve which appears to be nonsense

Generally speaking, if you reverse direction you count back the other way. So, count up to one junction, then count downwards around the triangle to the other junction.
As here - from Watford to Ricky starts at Watford at km 76.08, km descending to Croxley 74.10 and Watford E Jn 73.26. Where the kmage changes to 72.80, and increases to Watford N Jn 73.35 (matching kmage up the 'main line' from Baker St and Watford S Jn), Ricky 74.52 and on.

Remember these km figures are arbitrary progessive distances along the line, not really measured from anywhere in particular.
 
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