Commuting time map
 

Dear All

I hope I've come to the right place to ask this question.

I was commenting with a colleague recently how she (living in Sevenoaks)
takes a similar amount of time as me (in Raynes Park) to get into work
(we're based in Monument).

It made me wonder if anyone has re-designed a London travel map in terms of
time frame of reference - i.e. shortest time taken to get to a major London
station (e.g. Waterloo, Victoria, London Bridge, Liverpool Street etc.)
from around the south-east?

Just interested from a commuting viewpoint.

Regards
Richard

Commuting time map
 

Richard Dixon wrote:
Dear All

I hope I've come to the right place to ask this question.

I was commenting with a colleague recently how she (living in Sevenoaks)
takes a similar amount of time as me (in Raynes Park) to get into work
(we're based in Monument).

It made me wonder if anyone has re-designed a London travel map in terms of
time frame of reference - i.e. shortest time taken to get to a major London
station (e.g. Waterloo, Victoria, London Bridge, Liverpool Street etc.)
from around the south-east?

Just interested from a commuting viewpoint.

There is software available to companies involved in transport planning
which can plot "isochrones" (contours of time) of public transport
journey time to a specific point in London.

Unfortunately I can't immediately see any available on the internet.

--
Dave Arquati
Imperial College, SW7
www.alwaystouchout.com - Transport projects in London

Commuting time map
 

Dave Arquati wrote in
:

There is software available to companies involved in transport
planning which can plot "isochrones" (contours of time) of public
transport journey time to a specific point in London.

Unfortunately I can't immediately see any available on the internet.

Thanks - if you are able to find anything then please report back - it's
something I'd often wondered about and would have thought something would
have been available !

Many thanks
Richard

Commuting time map
 

Richard Dixon wrote:
Dave Arquati wrote in
:


There is software available to companies involved in transport
planning which can plot "isochrones" (contours of time) of public
transport journey time to a specific point in London.

Unfortunately I can't immediately see any available on the internet.


Thanks - if you are able to find anything then please report back - it's
something I'd often wondered about and would have thought something would
have been available !

Unfortunately it's not openly available as those companies use the
software to provide information to clients, e.g. when assessing an
office relocation scheme, they can provide the client with maps showing
which areas become closer temporally to the new location, and which
become further away, plotting the change in journey time as a set of
isochrones.

It's pretty interesting stuff; I did have a paper version of one, but
I'm not sure where I put it, otherwise I'd scan it in to show you.

--
Dave Arquati
Imperial College, SW7
www.alwaystouchout.com - Transport projects in London

Commuting time map
 

On Mon, 21 Feb 2005 20:17:15 +0000, Dave Arquati wrote:
It's pretty interesting stuff; I did have a paper version of one, but
I'm not sure where I put it, otherwise I'd scan it in to show you.

You get strange bubbles in areas where express trains stop. Slough and
Reading would be in the same isochrone for places in zone 1 for example,
but Maidenhead and Twyford would be "higher". Of course time of day and
mode of travel makes a difference too.
--
Everything I write here is my personal opinion, and should not be taken as fact.

Commuting time map
 

Richard Dixon wrote
[...]
I was commenting with a colleague recently how she (living in
Sevenoaks)
takes a similar amount of time as me (in Raynes Park) to get into
work
(we're based in Monument).

It made me wonder if anyone has re-designed a London travel map in
terms of
time frame of reference - i.e. shortest time taken to get to a major
London
station (e.g. Waterloo, Victoria, London Bridge, Liverpool Street
etc.)
from around the south-east?

Just interested from a commuting viewpoint.

I think it can't be done on a flat map without rearranging the order of
stations on each line.

Thus your Raynes Park (23' am peak) will have to be shown as further
out than Surbiton (18') as will Wimbledon (19').

Commuters from West Byfleet were complaining that with the new
timetable they had only stopping trains in the morning peak (40') but
they do have a fast return service (26'). So West Byfleet must be shown
as further out than Wokng (26' & 23') and possibly as far out as
Farnborough (36' & 39').

Best of luck to anyone trying to generate such a map.

--
Mike D

Commuting time map
 

"Michael R N Dolbear" wrote in message
news:01c51865$f9eab800$LocalHost@default...


Richard Dixon wrote
[...]
I was commenting with a colleague recently how she (living in
Sevenoaks)
takes a similar amount of time as me (in Raynes Park) to get into
work
(we're based in Monument).

It made me wonder if anyone has re-designed a London travel map in
terms of
time frame of reference - i.e. shortest time taken to get to a major
London
station (e.g. Waterloo, Victoria, London Bridge, Liverpool Street
etc.)
from around the south-east?

Just interested from a commuting viewpoint.

I think it can't be done on a flat map without rearranging the order of
stations on each line.

Thus your Raynes Park (23' am peak) will have to be shown as further
out than Surbiton (18') as will Wimbledon (19').

Commuters from West Byfleet were complaining that with the new
timetable they had only stopping trains in the morning peak (40') but
they do have a fast return service (26'). So West Byfleet must be shown
as further out than Wokng (26' & 23') and possibly as far out as
Farnborough (36' & 39').

Best of luck to anyone trying to generate such a map.

--
Mike D

You do it like a weather chart or OS map with contours. The contours
represent the points of equal time and yes some places further out will
have less travel minutes.
peter

Commuting time map
 

peter wrote:

I think it can't be done on a flat map without rearranging the order of
stations on each line.

Thus your Raynes Park (23' am peak) will have to be shown as further
out than Surbiton (18') as will Wimbledon (19').

Commuters from West Byfleet were complaining that with the new
timetable they had only stopping trains in the morning peak (40') but
they do have a fast return service (26'). So West Byfleet must be shown
as further out than Wokng (26' & 23') and possibly as far out as
Farnborough (36' & 39').

Best of luck to anyone trying to generate such a map.

--
Mike D


You do it like a weather chart or OS map with contours. The contours
represent the points of equal time and yes some places further out will
have less travel minutes.
peter

However the contours on an OS map (and AFAIK isobars on a weather chart)
never touch let alone cross. Whereas, in the example that Mike gave,
the isochrones will have to cross. That will make it rather hard to read.

Commuting time map
 

"Stephen Osborn" wrote in message
...

However the contours on an OS map (and AFAIK isobars on a weather chart)
never touch let alone cross.

They can touch, but they can't cross.

Whereas, in the example that Mike gave,
the isochrones will have to cross.

No, they won't. It's just the same as a weather map, it's just a map where
every point has a real number associated with it. Draw two isochrones
crossing each other, write various times on the isochrones and on the spaces
between them, and you'll see that it can't happen.

--
John Rowland - Spamtrapped
Transport Plans for the London Area, updated 2001
http://www.geocities.com/Athens/Acro...69/tpftla.html
A man's vehicle is a symbol of his manhood.
That's why my vehicle's the Piccadilly Line -
It's the size of a county and it comes every two and a half minutes

Commuting time map
 

John Rowland wrote:
"Stephen Osborn" wrote in message
...

However the contours on an OS map (and AFAIK isobars on a weather chart)
never touch let alone cross.

They can touch, but they can't cross.

I think you are wrong there.

Contours mark places of equal height. If two contours touch at any one
point then, de definito, they have to touch at *all* points, so the two
contours become one contour.

Whereas, in the example that Mike gave,
the isochrones will have to cross.

No, they won't. It's just the same as a weather map, it's just a map where
every point has a real number associated with it. Draw two isochrones
crossing each other, write various times on the isochrones and on the spaces
between them, and you'll see that it can't happen.

I was accepting Mike's point that "I think it can't be done on a flat
map without rearranging the order of stations on each line."

Using Mike's example, a 'railway straight line' runs Wimbledon, Raynes
Park & Surbiton in that order. The isochrone passes through Wimbledon &
Surbiton (ignoring the 1 minute difference) but not through Raynes Park.

That arrangement is possible on an OS map or weather chart as, say, two
maxima (M) can be separated by a minimum (m) so there will be places
with the same value but they are not linked by a contour / isobar. For
example a1 & a2 in the diagram below:

a b a
a a b b a a

a M a1 b m b a2 M a

a a b b a a
a b a

Here the contours / isobars that a1 & a2 sit on have different centres.

For a travel map to be of use, every point on it has to share share the
same centre.

regards

Stephen

Commuting time map
 

Richard Dixon wrote:

Dear All

I hope I've come to the right place to ask this question.

I was commenting with a colleague recently how she (living in Sevenoaks)
takes a similar amount of time as me (in Raynes Park) to get into work
(we're based in Monument).

It made me wonder if anyone has re-designed a London travel map in terms of
time frame of reference - i.e. shortest time taken to get to a major London
station (e.g. Waterloo, Victoria, London Bridge, Liverpool Street etc.)
from around the south-east?

Just interested from a commuting viewpoint.

I've seen such a map, but I can't remember exactly where, though it may
have been North Greenwich station. There were two versions: one showing
the situation before the Jubilee was extended, and one after.

Commuting time map
 

"Dave Arquati" wrote in message

[snip]

There is software available to companies involved in transport
planning
which can plot "isochrones" (contours of time) of public transport
journey time to a specific point in London.

Unfortunately I can't immediately see any available on the
internet.

When I joined my last company in 1988 the personnel dept had a
printed map for London's public transport, mostly oriented to trains
coming in from outer suburbia, as I recall. The map was ancient
then, disintegrating, and held together with sellotape. I don't
remember who published it. As a child, I remember seeing pre WW II
atlases, old then, with maps of Britain, coloured like contour maps,
showing time to reach London by train.

I think the newer versions of Autoroute do isochrones for cars, and,
of
course, bikes.

There's something funny, though, about the numbers Autoroute produces
if you send it out on a bike at 10 mph.

Every now and again I see "accessibility maps" put out by London's
planning or transport people. I think they credit it to a program
they have called PTAL, or some such. I wonder if you could demand a
copy of the program under the Freedom of Information Act.

Jeremy Parker

Commuting time map
 

Aidan Stanger wrote:
Richard Dixon wrote:


Dear All

I hope I've come to the right place to ask this question.

I was commenting with a colleague recently how she (living in Sevenoaks)
takes a similar amount of time as me (in Raynes Park) to get into work
(we're based in Monument).

It made me wonder if anyone has re-designed a London travel map in terms of
time frame of reference - i.e. shortest time taken to get to a major London
station (e.g. Waterloo, Victoria, London Bridge, Liverpool Street etc.)
from around the south-east?

Just interested from a commuting viewpoint.


I've seen such a map, but I can't remember exactly where, though it may
have been North Greenwich station. There were two versions: one showing
the situation before the Jubilee was extended, and one after.

I remember there used to be a computer terminal in the London Transport
Museum which showed you the Tube map versus a geographical one and an
isochronal one. The isochronal one didn't actually show the lines
though; it just showed points for the major centres like Harrow.

--
Dave Arquati
Imperial College, SW7
www.alwaystouchout.com - Transport projects in London

Commuting time map
 

Jeremy Parker wrote:
"Dave Arquati" wrote in message

[snip]

There is software available to companies involved in transport

planning

which can plot "isochrones" (contours of time) of public transport
journey time to a specific point in London.

Unfortunately I can't immediately see any available on the

internet.

When I joined my last company in 1988 the personnel dept had a
printed map for London's public transport, mostly oriented to trains
coming in from outer suburbia, as I recall. The map was ancient
then, disintegrating, and held together with sellotape. I don't
remember who published it. As a child, I remember seeing pre WW II
atlases, old then, with maps of Britain, coloured like contour maps,
showing time to reach London by train.

I think the newer versions of Autoroute do isochrones for cars, and,
of
course, bikes.

There's something funny, though, about the numbers Autoroute produces
if you send it out on a bike at 10 mph.

Every now and again I see "accessibility maps" put out by London's
planning or transport people. I think they credit it to a program
they have called PTAL, or some such. I wonder if you could demand a
copy of the program under the Freedom of Information Act.

PTAL is a scoring system from 1 (or perhaps zero?) to 6, with 6 being
the highest level of public transport accessibility. The southern
portion of the King's Cross development (developers: Argent) has a PTAL
score of 6, as by the time it is built, it will probably have the best
public transport accessibility in the entire country.

--
Dave Arquati
Imperial College, SW7
www.alwaystouchout.com - Transport projects in London

Commuting time map
 

Stephen Osborn wrote:
John Rowland wrote:
"Stephen Osborn" wrote in message
...

However the contours on an OS map (and AFAIK isobars on a weather
chart)
never touch let alone cross.

They can touch, but they can't cross.

I think you are wrong there.

Contours mark places of equal height. If two contours touch at any
one
point then, de definito, they have to touch at *all* points, so the
two
contours become one contour.

This is a correct argument that two contours _indicating the same
height_ must be coincident if they have at least one point in common;
however consider contours marking _different_ heights; these can
coincide on a non-empty set of points (eg along a vertical cliff)
without necessarily coinciding everywhere.

--
Larry Lard
Replies to group please

Commuting time map
 

Larry Lard wrote:
Stephen Osborn wrote:

John Rowland wrote:

"Stephen Osborn" wrote in message
...


However the contours on an OS map (and AFAIK isobars on a weather

chart)

never touch let alone cross.

They can touch, but they can't cross.

I think you are wrong there.

Contours mark places of equal height. If two contours touch at any

one

point then, de definito, they have to touch at *all* points, so the

two

contours become one contour.


This is a correct argument that two contours _indicating the same
height_ must be coincident if they have at least one point in common;
however consider contours marking _different_ heights; these can
coincide on a non-empty set of points (eg along a vertical cliff)
without necessarily coinciding everywhere.
--

That is true for a _literally_ vertical cliff, which does not actually
occur in nature.

Can you think of any other case that would be true (should "eg along a
vertical cliff" actually have been "ie along a vertical cliff")?


Also I still believe that, to make an accurate time map without
rearranging the order of stations on each line, the isochrones would
have to cross not just touch.


regards

Stephen

Commuting time map
 

On Tue, 22 Feb 2005, Stephen Osborn wrote:

Larry Lard wrote:
Stephen Osborn wrote:

John Rowland wrote:

"Stephen Osborn" wrote in message
...

However the contours on an OS map (and AFAIK isobars on a weather
chart) never touch let alone cross.

They can touch, but they can't cross.

Contours mark places of equal height. If two contours touch at any
one point then, de definito, they have to touch at *all* points, so
the two contours become one contour.

This is a correct argument that two contours _indicating the same
height_ must be coincident if they have at least one point in common;
however consider contours marking _different_ heights; these can
coincide on a non-empty set of points (eg along a vertical cliff)
without necessarily coinciding everywhere.

That is true for a _literally_ vertical cliff, which does not actually
occur in nature.

It might happen that there are no perfectly vertical cliffs, but i don't
think it's impossible in principle, so that doesn't matter.

Also, you do get cliffs like this:

---------/
/
cliff /
/
/
/
/-------
| sea
|

Which are a bit of a problem, as the altitude is discontinuous as you go
from left to right - it goes from X feet in the air to zero without there
being any intervening points.

tom

PS It's best not to put a "-- " before your reply; well-brought-up news
software will trim everything below that from a reply.

--
Destroy - kill all hippies.

Commuting time map
 

"Larry Lard" wrote in message
oups.com...
Stephen Osborn wrote:
John Rowland wrote:
"Stephen Osborn" wrote in message
...

However the contours on an OS map
(and AFAIK isobars on a weather chart)
never touch let alone cross.

They can touch, but they can't cross.

I think you are wrong there.

Contours mark places of equal height. If two contours
touch at any one point then, de definito, they have to
touch at *all* points, so the two
contours become one contour.

This is a correct argument that two contours
_indicating the same height_ must be coincident
if they have at least one point in common;

No. There are many "saddle" points in the landscape where, say, the land is
lower to the north and south, and higher to the east and west. The contour
which marks the height of the saddle point runs away from the saddle point
in 4 directions. It would be perverse to describe the contour as crossing
itself, but the contour could meaningfully be described as touching itself
at this one point. This is as true for a map of isochrones or isobars.

--
John Rowland - Spamtrapped
Transport Plans for the London Area, updated 2001
http://www.geocities.com/Athens/Acro...69/tpftla.html
A man's vehicle is a symbol of his manhood.
That's why my vehicle's the Piccadilly Line -
It's the size of a county and it comes every two and a half minutes

Commuting time map
 

John Rowland wrote:
"Larry Lard" wrote in message
oups.com...
Stephen Osborn wrote:
John Rowland wrote:
"Stephen Osborn" wrote in
message
...

However the contours on an OS map
(and AFAIK isobars on a weather chart)
never touch let alone cross.

They can touch, but they can't cross.

I think you are wrong there.

Contours mark places of equal height. If two contours
touch at any one point then, de definito, they have to
touch at *all* points, so the two
contours become one contour.

This is a correct argument that two contours
_indicating the same height_ must be coincident
if they have at least one point in common;

No. There are many "saddle" points in the landscape where, say, the
land is
lower to the north and south, and higher to the east and west. The
contour
which marks the height of the saddle point runs away from the saddle
point
in 4 directions. It would be perverse to describe the contour as
crossing
itself, but the contour could meaningfully be described as touching
itself
at this one point. This is as true for a map of isochrones or
isobars.

Like this, yes? :

[fixed width font needed]
numbers are heights

0 -1 -2 -3 -2 -1 0
1 0 -1 -2 -1 0 1
2 1 0 -1 0 1 2
3 2 1 0 1 2 3
2 1 0 -1 0 1 2
1 0 -1 -2 -1 0 1
0 -1 -2 -3 -2 -1 0

Surely in this situation there is only one contour, though, and it is
X-shaped. If you want to argue that there are two contours meeting in
the middle, how do you decide whether it's a meeting a , or a ^
meeting a v ?

Anyway, I'm not really sure this branch of this thread (?) has anything
useful to say about the original problem, as raised by Michael Dolbear:
"I think it can't be done on a flat map without rearranging the order
of
stations on each line."


--
Larry Lard
Replies to group please

Commuting time map
 

"Larry Lard" wrote in message
ups.com...

John Rowland wrote:
"Larry Lard" wrote in message
oups.com...

There are many "saddle" points in the landscape where,
say, the land is lower to the north and south, and higher
to the east and west. The contour which marks the height
of the saddle point runs away from the saddle point
in 4 directions. It would be perverse to describe the
contour as crossing itself, but the contour could
meaningfully be described as touching itself
at this one point. This is as true for a map of
isochrones or isobars.

Like this, yes? :

[fixed width font needed]
numbers are heights

0 -1 -2 -3 -2 -1 0
1 0 -1 -2 -1 0 1
2 1 0 -1 0 1 2
3 2 1 0 1 2 3
2 1 0 -1 0 1 2
1 0 -1 -2 -1 0 1
0 -1 -2 -3 -2 -1 0

Surely in this situation there is only one contour, though, and it is
X-shaped. If you want to argue that there are two contours meeting in
the middle, how do you decide whether it's a meeting a , or a ^
meeting a v ?

It's a ^ meeting a v. Look at the bigger picture, which would be like
this...

-------
--0-0--
-0+0+0-
--0-0--
-------

Anyway, I'm not really sure this branch of this thread (?) has anything
useful to say about the original problem, as raised by Michael Dolbear:
"I think it can't be done on a flat map without rearranging the order
of stations on each line."

His statement is so clearly wrong it's hard to argue with it until someone
explains why they think it's right. Every public point in the 2D space has a
scalar quantity associated with it, namely journey time from point X.
Mathematically this is identical to the contour maps, where every point
which is not inside a building has a scalar quantity associated with it,
namely height above sea level.

--
John Rowland - Spamtrapped
Transport Plans for the London Area, updated 2001
http://www.geocities.com/Athens/Acro...69/tpftla.html
A man's vehicle is a symbol of his manhood.
That's why my vehicle's the Piccadilly Line -
It's the size of a county and it comes every two and a half minutes

Commuting time map
 

John Rowland wrote:
"Larry Lard" wrote in message
ups.com...

John Rowland wrote:
"Larry Lard" wrote in message
oups.com...

There are many "saddle" points in the landscape where,
say, the land is lower to the north and south, and higher
to the east and west. The contour which marks the height
of the saddle point runs away from the saddle point
in 4 directions. It would be perverse to describe the
contour as crossing itself, but the contour could
meaningfully be described as touching itself
at this one point. This is as true for a map of
isochrones or isobars.

Like this, yes? :

[fixed width font needed]
numbers are heights

0 -1 -2 -3 -2 -1 0
1 0 -1 -2 -1 0 1
2 1 0 -1 0 1 2
3 2 1 0 1 2 3
2 1 0 -1 0 1 2
1 0 -1 -2 -1 0 1
0 -1 -2 -3 -2 -1 0

Surely in this situation there is only one contour, though, and it
is
X-shaped. If you want to argue that there are two contours meeting
in
the middle, how do you decide whether it's a meeting a , or a ^
meeting a v ?

It's a ^ meeting a v. Look at the bigger picture, which would be like
this...

-------
--0-0--
-0+0+0-
--0-0--
-------

I call this one 8-shaped contour, rather than two O-shaped contours
that touch at one point, but I would invest about zero effort in
arguing the toss.



Anyway, I'm not really sure this branch of this thread (?) has
anything
useful to say about the original problem, as raised by Michael
Dolbear:
"I think it can't be done on a flat map without rearranging the
order
of stations on each line."

His statement is so clearly wrong it's hard to argue with it until
someone
explains why they think it's right. Every public point in the 2D
space has a
scalar quantity associated with it, namely journey time from point X.
Mathematically this is identical to the contour maps, where every
point
which is not inside a building has a scalar quantity associated with
it,
namely height above sea level.

OK yes here I have been incorrectly thinking about something completely
other.

The 'it' you can't do without rearranging stations: make such a map
where commuting time is represented by distance;

What you *can* do: make such a map where isochrones are explicitly
overlaid on a geographical map, obviating any need to rearrange
stations.

At some point the 'it' changed and I failed to notice...

--
Larry Lard
Replies to group please

Commuting time map
 

On Wed, 23 Feb 2005 12:24:21 -0000, "John Rowland"
wrote:

"Larry Lard" wrote in message
oups.com...


Anyway, I'm not really sure this branch of this thread (?) has anything
useful to say about the original problem, as raised by Michael Dolbear:
"I think it can't be done on a flat map without rearranging the order
of stations on each line."

His statement is so clearly wrong it's hard to argue with it until someone
explains why they think it's right. Every public point in the 2D space has a
scalar quantity associated with it, namely journey time from point X.
Mathematically this is identical to the contour maps, where every point
which is not inside a building has a scalar quantity associated with it,
namely height above sea level.

That's broadly correct, but there is a difference in that whereas
height is a continuous quantity which has a value for *every*
location, journey time from X only has a value at discrete locations,
namely those where there are stations. So if you want to construct a
contour map (or a carpet plot) on a map of (say) England then you need
to interpolate between the values using a straight line or a
mathematical function that does it more smoothly.

Here's an example: if it takes 40 minutes to West Drayton and 25
minutes to Slough (I'm guessing these times), then where does the "30
minute contour" run? The answer is it passes somewhere between the two
stations. The exact position depends on what type of interpolation you
are using.

Note that you don't only have to interpolate between adjacent stations
on the same line - you need to interpolate between adjacent stations
irrespective of whether there is a railway between them, to allow you
to work out, say, where the 30 min contour line passes between Slough
and Gerrard's Cross.

There is software around that will do all this and take a set of
(X.Y) point and plot the Z value using contours. There are three steps
we need to take:

* obtain the Grid Reference (X,Y) of every station in (say) the
south-east. Does this data already exist?
* look up the fastest peak journey time (Z) from somewhere to each
station
* plot the resulting data as a contour plot

PaulO

Commuting time map
 

Stephen Osborn wrote:
John Rowland wrote:
"Stephen Osborn" wrote...

However the contours on an OS map (and AFAIK isobars on a weather chart)
never touch let alone cross.

They can touch, but they can't cross.

I think you are wrong there.

Contours mark places of equal height. If two contours touch at any one
point then, de definito, they have to touch at *all* points, so the two
contours become one contour.

You already have the counterexample of a vertical cliff. I have seen
those in nature - although not all of the cliff was vertical, there were
certainly parts that were, and they were definitely big and vertical
enough for contours to meet on the map.

Whereas, in the example that Mike gave,
the isochrones will have to cross.

No, they won't. It's just the same as a weather map, it's just a map where
every point has a real number associated with it. Draw two isochrones
crossing each other, write various times on the isochrones and on the spaces
between them, and you'll see that it can't happen.

I was accepting Mike's point that "I think it can't be done on a flat
map without rearranging the order of stations on each line."

Using Mike's example, a 'railway straight line' runs Wimbledon, Raynes
Park & Surbiton in that order. The isochrone passes through Wimbledon &
Surbiton (ignoring the 1 minute difference) but not through Raynes Park.

That arrangement is possible on an OS map or weather chart as, say, two
maxima (M) can be separated by a minimum (m) so there will be places
with the same value but they are not linked by a contour / isobar. For
example a1 & a2 in the diagram below:

a b a
a a b b a a

a M a1 b m b a2 M a

a a b b a a
a b a

Here the contours / isobars that a1 & a2 sit on have different centres.

For a travel map to be of use, every point on it has to share share the
same centre.

That statement is absolutely ridiculous! I'd go so far as to say the
converse is true: If they don't share the same centre then the map can
clearly display the information* and is therefore useful. If they do
share the same centre then it's impossible to display sufficient
information clearly, therefore the map would be useless.

They do have to share the same reference point, but that's all. I assume
what you were trying to say was that to be useful for determining the
time it would take to get between any two points on the map, every
contour has to share the same centre. If that is what you mean, I'm not
going to bother disputing it because it's pointless - software could do
the job a lot better than any map!


* The easiest way of doing so would be to set the background colour
according to how long it takes to get to the reference point. I expect
this would be referred to as isochromic isochrones!

Commuting time map
 

Aidan Stanger wrote:
Stephen Osborn wrote:

John Rowland wrote:

"Stephen Osborn" wrote...


However the contours on an OS map (and AFAIK isobars on a weather chart)
never touch let alone cross.

They can touch, but they can't cross.

I think you are wrong there.

Contours mark places of equal height. If two contours touch at any one
point then, de definito, they have to touch at *all* points, so the two
contours become one contour.


You already have the counterexample of a vertical cliff. I have seen
those in nature - although not all of the cliff was vertical, there were
certainly parts that were, and they were definitely big and vertical
enough for contours to meet on the map.


Whereas, in the example that Mike gave,
the isochrones will have to cross.

No, they won't. It's just the same as a weather map, it's just a map where
every point has a real number associated with it. Draw two isochrones
crossing each other, write various times on the isochrones and on the spaces
between them, and you'll see that it can't happen.

I was accepting Mike's point that "I think it can't be done on a flat
map without rearranging the order of stations on each line."

Using Mike's example, a 'railway straight line' runs Wimbledon, Raynes
Park & Surbiton in that order. The isochrone passes through Wimbledon &
Surbiton (ignoring the 1 minute difference) but not through Raynes Park.

That arrangement is possible on an OS map or weather chart as, say, two
maxima (M) can be separated by a minimum (m) so there will be places
with the same value but they are not linked by a contour / isobar. For
example a1 & a2 in the diagram below:

a b a
a a b b a a

a M a1 b m b a2 M a

a a b b a a
a b a

Here the contours / isobars that a1 & a2 sit on have different centres.

For a travel map to be of use, every point on it has to share share the
same centre.


That statement is absolutely ridiculous! I'd go so far as to say the
converse is true: If they don't share the same centre then the map can
clearly display the information* and is therefore useful. If they do
share the same centre then it's impossible to display sufficient
information clearly, therefore the map would be useless.

They do have to share the same reference point, but that's all. I assume
what you were trying to say was that to be useful for determining the
time it would take to get between any two points on the map, every
contour has to share the same centre. If that is what you mean, I'm not
going to bother disputing it because it's pointless - software could do
the job a lot better than any map!


* The easiest way of doing so would be to set the background colour
according to how long it takes to get to the reference point. I expect
this would be referred to as isochromic isochrones!

That's the way the isochrones I've seen have done it. It makes for a
very clear and interesting picture. Comparing the difference in journey
times to two locations is also done this way (i.e. set the isochrones as
the difference in journey time, +/-, for reaching point B compared to
reaching point A).

--
Dave Arquati
Imperial College, SW7
www.alwaystouchout.com - Transport projects in London

Commuting time map
 

Larry Lard wrote
[...]
The 'it' you can't do without rearranging stations: make such a map
where commuting time is represented by distance;

What you *can* do: make such a map where isochrones are explicitly
overlaid on a geographical map, obviating any need to rearrange
stations.

At some point the 'it' changed and I failed to notice...

Yes. Thank you.

I really didn't do this on purpose.

The OP referred to distorted maps where travel time to a central point
was represented by distance.

John Rowland and others (reference to 'bubbles') were considering
overlays on standard geographical maps.

http://www.sciencenews.org/articles/20040828/bob8.asp and links
for explanation/discussion of weird maps, based on population and so
forth.

--
Mike D

Commuting time map
 

In article ,
Paul Oter wrote:
Here's an example: if it takes 40 minutes to West Drayton and 25
minutes to Slough (I'm guessing these times), then where does the "30
minute contour" run?

A five minute walk from Slough Station.

Next?

--
Mike Bristow - really a very good driver

Commuting time map
 

Dave Arquati wrote:
Aidan Stanger wrote:

Stephen Osborn wrote:

snip John Rowland wrote:

I think you are wrong there.

Contours mark places of equal height. If two contours touch at any one
point then, de definito, they have to touch at *all* points, so the two
contours become one contour.

You already have the counterexample of a vertical cliff. I have seen
those in nature - although not all of the cliff was vertical, there were
certainly parts that were, and they were definitely big and vertical
enough for contours to meet on the map.

I am still not convinced you will find a natural cliff that is *truly*
vertical (e.g. measured by a plumb line) for more than 10 metres, in
order to have the contour lines coincident.

I would be fascinated if you can think of an example where this is true.

For a travel map to be of use, every point on it has to share share the
same centre.


That statement is absolutely ridiculous!

Yes it is, isn't it. I had fallen into the same trap as Larry Lard (in
an earlier post) had and was thinking of the distance from the centre
showing the travelling time. Probably too much time looking at LU zonal
maps!

this would be referred to as isochromic isochrones!

Nice!

--

regards

Stephen

Commuting time map
 

Stephen Osborn wrote:
I am still not convinced you will find a natural cliff that is *truly*
vertical (e.g. measured by a plumb line) for more than 10 metres, in
order to have the contour lines coincident.

I would be fascinated if you can think of an example where this is
true.

http://www.climbvertigo.ca/location-first-face.htm seems to indicate that in
places, the cliff is actually overhanging.

Tim (tm)
--
tim at economic-truth.co.uk Xbox Live gamertag: Xexyz
http://www.economic-truth.co.uk - the students' economics resource
http://www.ugvm.org.uk - the uk.games.video.misc magazine
The talkabout network is denied permission to reproduce this post

Commuting time map
 

Tim Miller wrote:
Stephen Osborn wrote:

I am still not convinced you will find a natural cliff that is *truly*
vertical (e.g. measured by a plumb line) for more than 10 metres, in
order to have the contour lines coincident.

I would be fascinated if you can think of an example where this is
true.


http://www.climbvertigo.ca/location-first-face.htm seems to indicate that in
places, the cliff is actually overhanging.

Tim (tm)

Yes but that is not vertical so the contour lines (of different heights)
would not be coincident.

I am struggling to get my mind around how an overhang should be shown on
an OS map.

--

regards

Stephen

Commuting time map
 

Stephen Osborn wrote:

http://www.climbvertigo.ca/location-first-face.htm seems to indicate
that in places, the cliff is actually overhanging.

Yes but that is not vertical so the contour lines (of different
heights) would not be coincident.

I am struggling to get my mind around how an overhang should be shown
on an OS map.

It would involve contour lines crossing. Each would have to be clearly
labelled at every point.

Tim (tm)
--
tim at economic-truth.co.uk Xbox Live gamertag: Xexyz
http://www.economic-truth.co.uk - the students' economics resource
http://www.ugvm.org.uk - the uk.games.video.misc magazine
The talkabout network is denied permission to reproduce this post

Commuting time map
 

"Jeremy Parker" wrote in message
...

Every now and again I see "accessibility maps" put out by London's
planning or transport people. I think they credit it to a program
they have called PTAL, or some such. I wonder if you could demand a
copy of the program under the Freedom of Information Act.

PTAL is not a program, it's an acronym.

"public transport accessibility level"

Ken's bunch are quite keen on it - basing parkign standards for development
on PTAL etc. See the London Plan, e.g. p.48

http://www.london.gov.uk/mayor/strat...n_plan_all.pdf