This troll needs more meat on its bones, so I'll feed it.
Many years ago, I was clocked on radar at a citizen's race as a last minute entry at 60 mph. I was wearing a parka and jeans. I stood straight up out of my tuck to kill speed before the radar spot because some curious spectator didn't believe there was a last minute entry and stepped into the course to look uphill and see for himself that I was on the way down. I had to slow to a level where I felt confident in dodging moving gates. I had a lot of confidence back then. 60 mph did indeed feel to me at the time very slow compared to speeds I had reached skiing cliffs on the back side of Mt. Washington BC.
Clink83 is right. If anyone really doesn't think a skier can ski faster if they don't have to make the gates, I have to wonder if they have a clue what they are talking about.
Data from Garmin GPSMap76CS track logs with 1 second recording:
First a typical day at Blue Mountain Collingwood, a relatively small vertical and no real steep runs, not really trying to do anything special, just put the GPS in my pocket and forgot about it and looked at the tracks later.
Next,a little experiment I did to see if the skis made much difference, comparing SG skis to SCs, trying to ski as fast as possible. No real difference in top speed, but speeds felt slow on the SGs and very fast on the SCs. I think the 82 mph is an aberation (it occurred immediately after landing some air and almost falling off the back side when the skis shot forwards), but fairly confident top speeds were over 60 mph. Mostly top speed is governed by air friction.
Another day at blue.
I have the both the Garmin 3 and Garmin 76 and have used both for mapping so I am going to draw from its experience starting over 30 years ago doing survey work in University.
Some of the tracks are straight lines (not talking about the lift lines which are consistent, but those which traverse the hill), which at Blue is not possible. This error is caused by Signal loss and depending on when the signal is locked again can lead to false speed readings. Secondly, with all GPS's partial signal can cause problems as well as they can move you 100ft in any given direction with just a few feet of actual movement. This is interesting to watch when you are doing real time plotting and comparison with Survey Equipment. Another thing that is interesting to watch is drift (when you are stationary) when the signals are intentional being scrambled, DGPS takes care of this within reason, but corrections can be made manually on a closed loop (similar to survey practices) as the drift is usually constant in one direction changing every few hours (learned through lots of field experience).
As to most of your speed I would suggest that they are likely accurate +/- a mile or 2 as I suspect I know which runs you have done this on and have achieved similar results (though not as fast on GS skis, likely on more crowded days) given the right day when no one is around at BLUE which can happen on week days.
@ THE REST
It is important to understand what and how the GPS does what it does to correctly interpret the data.
Ghost nice plot, hope you don't mind the analysis and making points describing what is happening.
Those really long straight lines off to the northeast in the first Blue Mountain tracks were me getting bord and trying to see how far I could make it before my built up momentum was diminished to zero. I made it all the way to what looked like some condos. You can see I don't skate very fast on the way back to the lift .
If you look at your track logs, it's easier to weed out faulty data. I also noticed from the track logs, that the reported speed is just horizontal distance travelled divided by time taken between two reporting points; it totally ignores any vertical speed and takes chord length, not arc length, so is an underestimate (if you have weeded out the dubious points). The max speed feature uses a doppler algorithm on the sat. signals, but there is no way to check it for reliability.