You can search google for "One Maps" and go to the website. They
have the train sectors and crossovers there. It is completely free,
although you would have to find out the slopes yourself. You can go
on the actual circle line and pen down the slopes because the
tunnel is illuminated. Just a suggestion!
No crossovers seen, though it helps to have info on the distance
between the tracks.
Apply Secondary 1 Geography skills is enough 
(I'm not indirectly insulting you, but it's true
it's geography skills)
Take a string (Any string is good) and measure roughly the
distance.
Then, from the start, to the end of the "section" of the string,
measure it with a ruler.
Then use the ruler to measure to the scale, then ta-da! You got
your distance.
It's more tedious work, but since it's Circle Line, too bad
:D
There is a ruler there. At the top of the page, there are 4
circular buttons. Choose the third, Tools, and select Measure.
