Speed revisited

Hello.

Last week I was skiing in northern Finland, and had a GPS receiver
attached to my upper arm. I've tested GPS:es earlier, and knowing the
conditions, the satellite visibility, and the position of the antenna
I can somehow rely to those numbers I clocked to the receiver.

I did several runs on a black diamond slope in order to gain high
speed. I know the safety rules, so I needed to have empty enough run
in order to let the speed grow. But anyhow this is what I did:

I first did large GS turns in tucked position and checked and reset
several times the max speed of the GPS. Typical max speed was around
80 kph (50 MPH). What I noticed, was that 60 kph (38 MPH) is very
easy to break, and that 75 kph (over 45 MPH) can be achieved
also quite easily.

Once in the Black run when I did again large fast GS turns, I found
the track totally empty. I tucked myself in a downhill position, and
counted slowly to five. Then I carefully rose up, and started to
carve tighter turns to lower my speed to safer level. The top speed
I clocked was 95,7 kph that is just short of 60 MPH.

That was with alpine gear (Rossi RPM 100). With tele gear I did only
controlled turns, since I didn't want to find myself in such speed that
I cannot handle with free heels. On the same Black run I clocked
83 kph (52MPH) with large radius tele turns.

It would be easy to break 100kph even without aero suit, but in order
to do that I would need a controlled situation where I could be sure
there are no surprises or people in front of me. Although the slope
I measured my speed there was good visibility, open fjall with no trees,
no crossing runs/tracks, I didn't feel too comfortable when going
over 90 kph. Up to 80 kph (50 MPH) it felt rather OK.

I have always thought what my speed is on the skis, and the earlier
thread here made me think how to test it. Now I have quite clear
understanding, what my speed is in different situations. It was partly
alarming experience to find how easily one can achieve highway speeds
in a populated slope. Even while carving turns. Be careful out there.

-Tero-

"Tero Ahlqvist" wrote in message
...
Hello.

Last week I was skiing in northern Finland, and had a GPS receiver
attached to my upper arm. I've tested GPS:es earlier, and knowing the
conditions, the satellite visibility, and the position of the antenna
I can somehow rely to those numbers I clocked to the receiver.

I did several runs on a black diamond slope in order to gain high
speed. I know the safety rules, so I needed to have empty enough run
in order to let the speed grow. But anyhow this is what I did:

I first did large GS turns in tucked position and checked and reset
several times the max speed of the GPS. Typical max speed was around
80 kph (50 MPH). What I noticed, was that 60 kph (38 MPH) is very
easy to break, and that 75 kph (over 45 MPH) can be achieved
also quite easily.

Once in the Black run when I did again large fast GS turns, I found
the track totally empty. I tucked myself in a downhill position, and
counted slowly to five. Then I carefully rose up, and started to
carve tighter turns to lower my speed to safer level. The top speed
I clocked was 95,7 kph that is just short of 60 MPH.

That was with alpine gear (Rossi RPM 100). With tele gear I did only
controlled turns, since I didn't want to find myself in such speed that
I cannot handle with free heels. On the same Black run I clocked
83 kph (52MPH) with large radius tele turns.

It would be easy to break 100kph even without aero suit, but in order
to do that I would need a controlled situation where I could be sure
there are no surprises or people in front of me. Although the slope
I measured my speed there was good visibility, open fjall with no trees,
no crossing runs/tracks, I didn't feel too comfortable when going
over 90 kph. Up to 80 kph (50 MPH) it felt rather OK.

I have always thought what my speed is on the skis, and the earlier
thread here made me think how to test it. Now I have quite clear
understanding, what my speed is in different situations. It was partly
alarming experience to find how easily one can achieve highway speeds
in a populated slope. Even while carving turns. Be careful out there.

-Tero-


Very interesting post. I had a GPS at Heavenly when I was there in
December, but forgot to take it out with me. The slopes were pretty empty
in the week, and I was really moving down some of the runs, I doubt
100klm/h, but the other day I did 70klm/h on the bike, and it felt like I
was doing at least that on the ski's.. after reading your post, I guess that
might have been possible..

I have to agree with you. There were other discussions in
RSA about this you might want to look at.

Important to note is to be sure use max speed function.
Don't try to watch the thing while you're skiing, it's a tough,
dangerous thing to do, especially at speeds which would
be interesting.

Also note that gps does not calculate vertical drop, so you're
actually going faster than the reading, but not by very much.

The fastest I did last year was 62 mph (add one half of mph to
mph to get rough kph), same story, empty run, safe runout, no
merging trails, no one in the way. Your grandma and everyone
else, including the five year old wedging straight down the hill go
25 mph. The typical airpeep skiing back to the lift with hands at
waist goes around 50mph. Warren Miller type backcountry
powder eleven cliff skiers are going around 60 to 80 mph
in that powder.

25 mph is nothing on skis, and a fall at that speed, on skis at
least, is usually a trivial incident. Yet, go 25 mph in your car,
open the door and step out, you'll get a different result. You
don't dare hit a stationary object at 25 on skis or a board.

Thanks for the post Tero.

"AH" wrote in message
...

"Tero Ahlqvist" wrote in
message ...
Hello.

Last week I was skiing in northern Finland, and had a GPS receiver
attached to my upper arm. I've tested GPS:es earlier, and knowing the
conditions, the satellite visibility, and the position of the antenna
I can somehow rely to those numbers I clocked to the receiver.

I did several runs on a black diamond slope in order to gain high
speed. I know the safety rules, so I needed to have empty enough run
in order to let the speed grow. But anyhow this is what I did:

I first did large GS turns in tucked position and checked and reset
several times the max speed of the GPS. Typical max speed was around
80 kph (50 MPH). What I noticed, was that 60 kph (38 MPH) is very
easy to break, and that 75 kph (over 45 MPH) can be achieved
also quite easily.

Once in the Black run when I did again large fast GS turns, I found
the track totally empty. I tucked myself in a downhill position, and
counted slowly to five. Then I carefully rose up, and started to
carve tighter turns to lower my speed to safer level. The top speed
I clocked was 95,7 kph that is just short of 60 MPH.

That was with alpine gear (Rossi RPM 100). With tele gear I did only
controlled turns, since I didn't want to find myself in such speed that
I cannot handle with free heels. On the same Black run I clocked
83 kph (52MPH) with large radius tele turns.

It would be easy to break 100kph even without aero suit, but in order
to do that I would need a controlled situation where I could be sure
there are no surprises or people in front of me. Although the slope
I measured my speed there was good visibility, open fjall with no trees,
no crossing runs/tracks, I didn't feel too comfortable when going
over 90 kph. Up to 80 kph (50 MPH) it felt rather OK.

I have always thought what my speed is on the skis, and the earlier
thread here made me think how to test it. Now I have quite clear
understanding, what my speed is in different situations. It was partly
alarming experience to find how easily one can achieve highway speeds
in a populated slope. Even while carving turns. Be careful out there.

-Tero-


Very interesting post. I had a GPS at Heavenly when I was there in
December, but forgot to take it out with me. The slopes were pretty empty
in the week, and I was really moving down some of the runs, I doubt
100klm/h, but the other day I did 70klm/h on the bike, and it felt like I
was doing at least that on the ski's.. after reading your post, I guess
that might have been possible..

foot2foot wrote:

Also note that gps does not calculate vertical drop, so you're
actually going faster than the reading, but not by very much.

That's kind of hard to believe, people use handheld GPS in aircrafts
too.

"foot2foot" wrote in message
...
Also note that gps does not calculate vertical drop, so you're
actually going faster than the reading, but not by very much.

GPS speed is an absolute speed in 3D space. Not the 'ground speed' nor
horizontal projection of the speed. So what it shows is the actual
speed you're going.

GPS measures the speed based on the doppler correction needed for
each individual visible satellite. So it's normally pretty accurate.
Since in vertical motion the satellite geometry is mostly one sided
(i.e. all the visible satellites are above you) both the vertical speed
accuracy and the vertical position accuracy (altitude) are worse than
the horizontal ones. So the flatter the mountain, the more accurate
the speed. The steeper you go, the error increases. But anyway the
error should be insignificant in this kind of speed measurements.

Also repeated tries giving approximately the same result add
reliability to the measurement. I've seen some odd numbers on the
GPS max speed field as well, but mostly in urban areas with poor
satellite visibility having lots of buildings, electric lines, tunnels
etc.

And of course I only checked the recorded max speed in the GPS. I had
the GPS in the sleeve pocket, and I concentrated fully in my skiing.

-Tero-

wrote:
foot2foot wrote:


Also note that gps does not calculate vertical drop, so you're
actually going faster than the reading, but not by very much.


That's kind of hard to believe, people use handheld GPS in aircrafts
too.


GPSers do indicate elevation, just don't calculate
vertical drop when in speed mode. At least mine doesn't.

It will calculate total vertical if you ask it to. As
will an Avocet altimeter watch.

Tero Ahlqvist wrote:

"foot2foot" wrote in message
...
Also note that gps does not calculate vertical drop, so you're
actually going faster than the reading, but not by very much.

GPS speed is an absolute speed in 3D space. Not the 'ground speed' nor
horizontal projection of the speed. So what it shows is the actual
speed you're going.

GPS measures the speed based on the doppler correction needed for
each individual visible satellite. So it's normally pretty accurate.
Since in vertical motion the satellite geometry is mostly one sided
(i.e. all the visible satellites are above you) both the vertical speed
accuracy and the vertical position accuracy (altitude) are worse than
the horizontal ones. So the flatter the mountain, the more accurate
the speed. The steeper you go, the error increases. But anyway the
error should be insignificant in this kind of speed measurements.

I worked for Magellan when the units were the approximate size and weight of
bricks and cost $2,000 for the basic model. It was fun to sit in my office
and watch the altitude change by tens of feet at each reading.

Also repeated tries giving approximately the same result add
reliability to the measurement. I've seen some odd numbers on the
GPS max speed field as well, but mostly in urban areas with poor
satellite visibility having lots of buildings, electric lines, tunnels
etc.

If you needed real accuracy you were encouraged to buy two units and take an
average. It was more complicated than that, of course.

And of course I only checked the recorded max speed in the GPS. I had
the GPS in the sleeve pocket, and I concentrated fully in my skiing.

Congratulations. I'd still like to know how fast I was going before I crashed
:-(

--
Cheers,
Bev
[] [] [] [] [] [] [] [] [] [] [] [] [] [] [] [] [] [] [] []
If voting could really change things, it would be illegal.
--Revolution Books, New York, New York

"VtSkier" wrote in message
...

GPSers do indicate elevation, just don't calculate
vertical drop when in speed mode. At least mine doesn't.


How did you determine this?

C.

So what do you think of the RPM 100s. I started skiing on mine this year
and love them.

"Tero Ahlqvist" wrote in message
...
Hello.

Last week I was skiing in northern Finland, and had a GPS receiver
attached to my upper arm. I've tested GPS:es earlier, and knowing the
conditions, the satellite visibility, and the position of the antenna
I can somehow rely to those numbers I clocked to the receiver.

I did several runs on a black diamond slope in order to gain high
speed. I know the safety rules, so I needed to have empty enough run
in order to let the speed grow. But anyhow this is what I did:

I first did large GS turns in tucked position and checked and reset
several times the max speed of the GPS. Typical max speed was around
80 kph (50 MPH). What I noticed, was that 60 kph (38 MPH) is very
easy to break, and that 75 kph (over 45 MPH) can be achieved
also quite easily.

Once in the Black run when I did again large fast GS turns, I found
the track totally empty. I tucked myself in a downhill position, and
counted slowly to five. Then I carefully rose up, and started to
carve tighter turns to lower my speed to safer level. The top speed
I clocked was 95,7 kph that is just short of 60 MPH.

That was with alpine gear (Rossi RPM 100). With tele gear I did only
controlled turns, since I didn't want to find myself in such speed that
I cannot handle with free heels. On the same Black run I clocked
83 kph (52MPH) with large radius tele turns.

It would be easy to break 100kph even without aero suit, but in order
to do that I would need a controlled situation where I could be sure
there are no surprises or people in front of me. Although the slope
I measured my speed there was good visibility, open fjall with no trees,
no crossing runs/tracks, I didn't feel too comfortable when going
over 90 kph. Up to 80 kph (50 MPH) it felt rather OK.

I have always thought what my speed is on the skis, and the earlier
thread here made me think how to test it. Now I have quite clear
understanding, what my speed is in different situations. It was partly
alarming experience to find how easily one can achieve highway speeds
in a populated slope. Even while carving turns. Be careful out there.

-Tero-

"DZN" wrote in message
...
So what do you think of the RPM 100s. I started skiing on mine this year
and love them.


Great, just Great!

I haven't yet been able to ski such speed the skis could not handle.
The thing I like the most is the consistency of the skis. When
demoing some other makes, you had to learn how the ski works on the
ice or in the soft snow. RPM100 just reads your thoughts and carves
always as fine as ever...

They are forgiving, but have a lots of performance. No wonder I read
somewhere that these skis were specified by Bode Miller when he still
skied Rossis. There was a special model "Bode One" just before he
changed to Atomics. It was said to be the ski that Bode would want
to ski himself. RPM100, Bode One, and Rossi 9X are the same ski with
different graphics.

-Tero-