Alti-track, SAS or TAS

[sparksPNT 0]

I am still a little unsure which of these settings on the alti-track is best form my skydiving. The manual is not as clear as I would like.
Does anybody have anymore info on these?

And which you prefer?

Weather forecast for tonight: dark

[phoenixlpr 0]

SAS speeds can be compared, because they are normalized.

[sundevil777 102]

The type of jumping you do is not important to this issue.

SAS is a speed that is normalized to a standard pressure/temp. TAS is not adjusted in this manner.

The normalizing is useful so that a person that jumps at a high altitude DZ can make a valid comparison to someone that jumps at a sea level DZ.

It would help a lot if we knew for sure whether the Neptune and others do an normalizing.

You can change the TAS/SAS setting at any time, the data from previous jumps will then be displayed differently.

People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am

[peek 21]

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(SAS or TAS) I am still a little unsure which of these settings on the alti-track is best form my skydiving.

I for one am delighted that you know the difference and care. Why? Well, www.pcprg.com/baro.htm, that's why.

Most people are simply clueless, and these devices are little more than a toy without this knowledge, (and a lot more.) Most people I ask don't even know how theirs is set up.

The best way to use them is to download the jump and analyze it.

[Chilly_Dk 0]

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SAS is a speed that is normalized to a standard pressure/temp. TAS is not adjusted in this manner.

The normalizing is useful so that a person that jumps at a high altitude DZ can make a valid comparison to someone that jumps at a sea level DZ.

This is correct. The TAS is the "True Airspeed" at any altitude = the vertical speed of an object relative to the surrounding air, regardless of the altitude.

Remember that this naturally will change during the skydive (because of the air pressure change, and change in air resistance). Therefore the first half of a skydive will register "faster" than the second part when using TAS.
This makes some people complain about their ProTrack showing that the base of the skydive slowed down in the end (Who hasn't heard that excuse? ).

Using SAS this can be avoided, since all altitudes are adjusted as if the complete skydive had been performed at a fixed air pressure and a fixed temperature, which corresponds to 4,000 feet ASL.
L&B has choosen 4000 feet, since most skydives ends around that altitude (not addressing all the low pullers out there )


Anyways, conclusion is; TAS shows your speed in relation to your current altitude, SAS adjusts to one specific altitude, and is a lot more comparable.



Do I make sense at all???

It's all right to have butterflies in your stomach. Just get them to fly in formation.

[bofh 0]

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Using SAS this can be avoided, since all altitudes are adjusted as if the complete skydive had been performed at a fixed air pressure and a fixed temperature, which corresponds to 4,000 feet ASL.

I don't think the temperature compensation works so good, since (at least on the alti-track), it seems to be measured via the pressure sensor's thermometer and since that one is inside the device it doesn't measure the outside temperature so good. Mine rarely goes under 18 degrees, even if the ambient temperature is a lot lower.

[jheadley 0]

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Remember that this naturally will change during the skydive (because of the air pressure change, and change in air resistance). Therefore the first half of a skydive will register "faster" than the second part when using TAS.
This makes some people complain about their ProTrack showing that the base of the skydive slowed down in the end (Who hasn't heard that excuse? ).

Using SAS this can be avoided, since all altitudes are adjusted as if the complete skydive had been performed at a fixed air pressure and a fixed temperature, which corresponds to 4,000 feet ASL.
L&B has choosen 4000 feet, since most skydives ends around that altitude (not addressing all the low pullers out there )


Anyways, conclusion is; TAS shows your speed in relation to your current altitude, SAS adjusts to one specific altitude, and is a lot more comparable.

This is all true but SAS also will just show a typcally slower speed all around. 114mph SAS seems to be sort of the "normal" speed for my RW dives, but then when I switch it to TAS or look at it in Jump-Track, it's much higher. Right now I'm looking at a graph and it says that at 7,000 feet AGL (don't know MSL, but it was at Dublin), 120mph TAS (The "Normal" speed for RW) would be 113mph SAS.

So if you set it to TAS, you'll always hear that one guy who always goes low complain about how the skydive "got slower" throughout the skydive, or if you set it to SAS, you'll just hear how the entire skydive was slow.

I think people put way too much emphasis on fall rate numbers in their little computers. I know one guy who says that a good 4 way has to move at exactly 122 mph. You hear people ask other people what their fall rate is. I think "slow, medium or fast" is enough of an answer, but I can't help but smile when people say things like "About 117 or 118" since there are obviously so many variables to that.

I typically set my pro track to SAS, but if I ever actually do look at a jump's fall rate (which is rare), I'll switch between SAS and TAS and take both into consideration.

[sundevil777 102]

When asked what my typical fallrate is, I always acknowledge that it is SAS. It is rare that the person that asked knows what that means.

Do any of the other freefall computers offer a normalized speed? I don't understand how they could not have this feature. When developing a product, you would think that they would at least examine what their competition offers and try to do as well if not better.

People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am

[peek 21]

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You hear people ask other people what their fall rate is. I think "slow, medium or fast" is enough of an answer, but I can't help but smile when people say things like "About 117 or 118" since there are obviously so many variables to that.

Yes, yes, yes! I found another person who understands!

That is exactly what I think when they quote me a specific number. (Actually, I don't smile. I roll my eyes.)

I would just rather hear them say "slow, medium or fast".

[phoenixlpr 0]

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I would just rather hear them say "slow, medium or fast".

And you might hear the question: "comparing to what?"

[peek 21]

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I would just rather hear them say "slow, medium or fast". [And you might hear the question: "comparing to what?"]

Yes, that would be a good question for some, but when "slow, medium, or fast" is useful is when someone, fopr example:

1. small or thin comes along and they say that their friend think they fast fairly fast, considering

2. someone short and round comes along and says that they can stay up with their thinner friends with the jumpsuit they are using

This is when I would much rather hear that (opinion from their friends) than I would some number that they probably don't understand.

Basically, it is an example of trusting the advance computational skills of an experienced skydiver's brain, (including the intuition part), rather than using the uninterpreted number from an unintelligent device.

(Hope that didn't sound too far out there.)

[sparksPNT 0]

Thanks for all the info!!

Weather forecast for tonight: dark

[billvon 2,996]

>Basically, it is an example of trusting the advance computational
> skills of an experienced skydiver's brain, (including the intuition
> part), rather than using the uninterpreted number from an
> unintelligent device.

The reading from a Pro-Track or equivalent device is just one more bit of data to be used when determining what the fallrate will be. It's useful because it's generally not subjected to regional biases. i.e. "I'm the fastest faller on my DZ!" isn't that useful if he jumps at an all-female DZ. Knowing he sees an SAS of 109 mph would be a lot more useful.

[CygnusX-1 43]

So, where is this all-female dropzone which you speak about???

• Quote

[kelpdiver 2]

heaven, if you're of faith.

[JohanW 0]

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[snip]

Using SAS this can be avoided, since all altitudes are adjusted as if the complete skydive had been performed at a fixed air pressure and a fixed temperature, which corresponds to 4,000 feet ASL AGL.

[snip]

There, fixed that for you.

Johan.
I am. I think.

[pilotdave 0]

Actually I think you broke it.

Dave

[jurgencamps 0]

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There, fixed that for you.

http://www.l-and-b.dk/pdf/english_protrack.pdf pg 41

ASL was correct, not AGL

[JohanW 0]

OK, I was wrong. It is calculated against a standardised sea level. Which is not the same as ASL there and then, but isn't AGL either.

It makes sense when you think about it (NO, I hadn't ). It's the only way you can compare readings from different places.

But it's still not ASL!

Johan.
I am. I think.

[Chilly_Dk 0]

It's all right to have butterflies in your stomach. Just get them to fly in formation.