garmin foretrex 401 as an alti/GPS

[LegoNinja 0]

Hey all,

Im looking at buying a garmin foretrex 401, to use as an alti/GPS unit and am wondering if anyone has had any experience with them. Will really only be used to get me home when in alot of cloud cover(jumping in controlled air space)

Also want to know if the alti on it is accurate in freefall?

Cheers

[Rugby82 0]

I don't have one but a lot of people around me use them all the time. They seem to do a good job as an alti. The only problem is that the batteries aren't lasting for that long (say about 10 hours). Here they are also used a lot by tandemmasters when jumping with heavy clouds.

Blue skies!

[phoenixlpr 0]

I used to have a garmin foretrex 301.
No, no, no and NO.

Why don't you jump with an umbrella or a backpack instead of a skydiving rig?
Than get an _altimeter_.

[skywombat 0]

Disclaimer: I have not seen this unit so I cannot speak about it directly.

That said, I would imagine your purpose-built altimeter is built to a higher standard of quality than a general-purpose GPS unit. It also probably does not undergo the same amount of manufacturer testing as an altimeter built specifically for parachuting. Moreover, is a complex piece of electronics and in general, embedded software tends to be notoriously bad.

The refresh latency may not be suited for fast descent (that is, you have no idea what the delay is between altitude change and display update). Finally, an integrated altimeter/GPS unit may try to do some tricks like calibrating the pressure offset to GPS altitude (which is not always reliable, depending on satellite positions and VDOP) rather than figuring out if you are on the ground and resetting to 0 or detecting that you are on an ascending plane and leaving the ground offset as is.

[phoenixlpr 0]

Quote

The refresh latency may not be suited for fast descent (that is, you have no idea what the delay is between altitude change and display update). Finally, an integrated altimeter/GPS unit may try to do some tricks like calibrating the pressure offset to GPS altitude (which is not always reliable, depending on satellite positions and VDOP) rather than figuring out if you are on the ground and resetting to 0 or detecting that you are on an ascending plane and leaving the ground offset as is.

FYI: garmin foretrex 401 has a barometric altimeter.
Still: no.no, NO

[AStack75 4]

I often jump with a Garmin Forerunner 305. It's a running watch and I bought it for when I go running. But have been jumping with it. I have a target set on the peas of my DZ and then I basically have it set on navigation mode with that target as the destination. Then the watch will show you a compass with the arrow pointed to the DZ and your distance in miles and time from the DZ (based on your current speed).

I pretty much just use the watch to log jumps and also for when I'm sitting on the plane and wondering where we are relative to the DZ. I definitely wouldn't use it as an altimeter though.

One thing I did find very useful about it is if you do a cross country. It makes finding the DZ a little easier. Also it's nice to see how far away you are.

But I pretty much just only look at it on the plane and just use it as a GPS logger (if I remember to hit the start button before I jump).

You download your jumps (runs) afterwards and you can see an image in Google Earth of where your were horizontally and also a chart of your elevation and speeds.

I'm not familiar with the Foretrex, but I'm assuming it is somewhat similar to the Forerunner. In which case I would say hell no to using it as an altimeter.

[dragon2 0]

I have one, haven't jumped it yet due to health problems. Only reason to get it IMO is indeed, cloud cover.

We have 2 people jumping here who always use one. One loves it, the other wouldn't buy it again. It's a lot of hassle with having to set the GPS each jump, zeroing the alti, watching the battery level and it's not that good an alti in any case.

I wouldn't recommend it for a freefall alti, unless maybe you're a tandemmaster where you have all the time in the world to watch your alti or tandem videoflyer where you don't have to, much. I only got mine because I very rarely look at my alti in freefall anyway, being mostly a (tandem) camera flyer, and I will probably use my neptune as the alti with the foretrex purely as a GPS.

ciel bleu,
Saskia

[LouDiamond 1]

As has been stated, no, it's not a good idea to use it as a stand alone device. If you need/want the GPS capability thats fine but you need to use a stand alone altimeter alongside of it.

"It's just skydiving..additional drama is not required"
Some people dream about flying, I live my dream
SKYMONKEY PUBLISHING

[Hellis 0]

Cheaper option
Very accurate, except inside the airplane where the metal makes the compass show 180 degrees off.

However as an altimeter, no. Use a real altimeter.

[AStack75 4]

Quote

Cheaper option
Very accurate, except inside the airplane where the metal makes the compass show 180 degrees off.

It's probably nothing to do with the metal. Mine is off 180 degrees in the plane also but that's because I'm facing the back of the plane. The watch (or keychain in your case) doesn't know what direction you are facing. It assumes you are facing the direction you are moving since that's how most humans travel. So you should look at the compass as if you were sitting in the pilot's seat.

[Hellis 0]

No. Thats not my experience.

Even if im on my kees facing forward it will still show 180 degrees off.
However, if im sitting in the middle of the plane and leening towards the center of the airplane it will be correct.
Thats why i assume its the metal.

But it could be different on your GPS.

[LegoNinja 0]

Hey everyone,

thanks for taking the time to help me out with this :)

Decided im gonna run a 'Skydiving alti' and later will get a 401 to use just as a GPS.

Cheers team

[ljwobker 2]

I have hundreds of jumps with one of these Garmins and use them to log wingsuit jumps and cross country canopy jumps, as well as just being a gadget freak (I get to harass the pilot if he misses the spot, etc ;-)

The altimeter is *very* unreliable when compared to a wristmount barometric one. UNDER NO CIRCUMSTANCES should you rely on this device to save your life... it's simply not designed to deal with pressure changes this quick.

For tracking position for later use or other such things it's awesome, but not as a replacement for a specifically designed altimeter.

HTH.