Quote from jorgez:
Nothing clever I am afraid to mention, nor indeed is it worthy of being declared a secret. It is simply a build up of bid-ask from tick level.
I do not use it for intraday trading because it requires assumptions and I do not care for assumptions whilst trading.
But like a lot of things, the overs and unders tend to iron themselves out as the picture expands into a macro view, and providing you do not alter the format then the relativities contained within the macro view are maintained.
Every picture tells a story