I don't go to the extent of creating speed maps as such but I agree that it can be very useful to know which horses are leaders - particularly at tracks like Moonee Valley where the on-pace horses generally win.

As far as determining which horses are leaders, on-pace, backmarkers etc I think the best way to go is to use the "in Running" figures that most form viewing/analysing software provide in their horse history. It is easy to look at the early positions (left hand columns) and see where a horse is usually placed.
It only takes a few minutes to do each race and this way you are making your own decisions - not some journalist's