Last Friday at Belmont is a very good example of the kind of thing I discussed in the DRF Expo presentation, which can be found in the archives here. The track was listed as fast throughout, with no obvious weather until just before the last race, when it started to rain. To someone who doesn\'t get complete information about track maintenance, and/or makes the assumption that without a weather event track speed stays constant, the horses \"must\" have been running over the same track all day, in terms of track \"speed\".
In point of fact, an awful lot was going on. They watered the track before each of the first 5 races, and the track stayed basically the same speed (a little slower for the fifth). After the fifth they sealed the track, presumably in anticipation of the rain that came later, but then unsealed it again after the sixth (a grass race), and did not water the track again for the rest of the day. The track got MUCH slower-- by the end of the card, it was 12 points slower than when it began.
Now, accurate weather and groundskeeping info helps me piece together what is happening. But in the end it doesn\'t help me determine HOW fast the track was-- you can only do that by looking at the figure histories of the horses. And again-- if you either didn\'t have the info, or made the ASSUMPTION that since the track was fast and there was no significant weather the track must not have changed, you had to get it wrong. In all probability you would use what amounts to an average variant for the day, giving horses in the early races figures that are much too good, and later ones much too bad.