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I have been looking at my exit data recently and comparing different suits.

How are others measuring exit performance? My idea is to measure the horizontal distance covered in the first 200m of altitude.

The new flysight software for mac osx makes it much easier to compare exit performance (a year or so ago it wasn't so great -- not sure when the update happened but PSA: update your software). In the past I picked out 400-600ft as an arbitrary horizontal distance and would see how far vertically I've dropped for reference. I compared my Aura1+Aura2 starts with Richard Webb's aura start profile data (http://www.basejumper.com/cgi-bin/forum//attachment/87602). It was eerily similar. My worst exit on an evening jump with a slight downdraft had the same vertical distance at 500ft. Everything else was surprisingly in the same range as the green curves. The three other guys I was flying with mostly this summer also found that a slightly steeper or more shallow exit had nowhere near the same impact as weather conditions. Sometimes we'd have a steeper exit but the start arc would be better than what we felt was the perfect exit in different conditions.

I made a folder for each day of the summer, and put flysight files in the appropriate folder at the end of the day. My back-facing vids and flysight data show a correlation between how fast the tail wing inflates cleanly (no fluttering) and a shorter start arc.

It would be great if Matt G would provide a free pdf-version of the Great Book of Base Second Edition. He proposes an elegant definition of a start arc (pg. 177, ed. 2):

I think by using a single point metric you lose quite a bit of information about the start.

I think the best way to compare is to get a full graphical representation of the whole first 300m or so. This is something that you can quite easily do with excel. I can send you a very simple spreadsheet if you'd like. But I know others have much better ones.

If you do stick with a single point metric, it might be worth complementing this with a speed measurement at that point, to get some kind of indication of the energy you are carrying through the start.

I've typically been using the 1:1 method, and I've found it works ok. But it's not without flaws.

Useful info, thanks guys. Excel would be appreciated, grazie!

I agree... having looked at the total sum of 30+ start curves on the same suit in similar conditions, I was able to generate an easy to memorize curve of my 95-percentile start. For me currently, it's:
Horiz/Vertical (ft):
100/200
200/300
300/400
400/450

With these easy pairs in my head, I can profile any exit with a laser, and calculate margins in 5 minutes. If I like the margins, then it's just wait for proper conditions, and fly!

Richard

In my (and others) opinion flysight track logs can look unrealistically good for the start of the jump. Maybe I'm saying something really obvious... but it would be a mistake to jump something based only on your track logs. Best is to progress gradually through harder starts and so build up a library of profiles that you know you can jump and you know how they feel (scary or not). Also on some jumps you can laser points on the side and use those as a reference for measuring performance.

Being skeptical of Flysight track logs, and any other tracking device, is a great way to stay alive! When I was first developing my current methodology for profiling exits and flights accurately, we routinely jumped with a Flysight each, plus a phone GPS app, plus maybe a normal Garmin GPS. Then we'd compare the data from all devices on the load looking for inconsistencis and holes.
In my opinion, a properly calibrated Flysight with current firmware is an invaluable tool for building your own personal start profile. Once you know exactly what YOU can do 95% of the time with a set of given conditions, your confidence on a new exit skyrockets.

Richard

Very cool to see that data. However 95% confidence sounds kinda sketchy to me, since I'd personally like to survive more than 20ish jumps...

I'm curious have you logged enough jumps to know how that compares to a 99th percentile profile? 99.9%?

95-percentile jump... then add your own personal margins. Those margins can be generous, or tight, depending on your proficiency, currency, conditions, gear, and a million other variables. Some folks may want a 200' margin at all times added to their 95% start, others may choose more, or less.

My point is: Identify as accurately as possibly what YOUR start arc is 95% of the time. Then use that as baseline to work from.

Did you pick 95% based on +/- 2 standard deviations?

I don't wingsuit, just curious about your M.O.

Can you say a bit more precisely how you've found the tracks to look unrealistically good at the start? What are you comparing against?

Michael

Hey Michael. So my flysight logs show a start arc varying between -80,80 metres and -140,140... averaging about -120,120. So 120 metres horizontal at 120 down.

Points that I have lasered...
Usually I am about 10m higher than -137, 85
Usually I am about level with -160, 170

My sample is small, and not a proper test/validation. Flysight is awesome... I just think the start arcs I get are a bit optimistic. And I have never used my track logs when deciding whether or not to jump something.

If you want I can send you my flysight logs.

Cheers, David

I'd love to take a look at the logs. My email is "michael at flysight dot ca".

The moment after exit is always a bit tricky for GPS, since it suddenly loses half the sky. The FlySight logs a few parameters which should help estimate the precision of the data--in the "hAcc", "vAcc" and "sAcc" columns--but these are estimates based on, e.g., signal strength and satellite geometry, so they can be fooled, too. I'm curious to see how they respond right after your exit.

Michael

This is by far the best and easiest to use tool for viewing and comparing your start profiles

https://www.facebook.com/FlySafeApp/?fref=ts

I think it's also a step in the right direction in regards to your exit database post.

Also, I don't think you can make valid comparisons between exits at different altitudes. It plays a much larger role in the start than most people give it credit for. I don't have enough data to accurately quantify it yet, but i would estimate it adds at least 20m per 1000m altitude to your start arc

Wow -- thanks to everyone who helped make this. This is great.

Has anyone figured out the formula for the location(Lat/Long)?

I would like to be able to stand at an exit..collect the stationary point...throw that first point, into a flight of my choosing, and extrapolate the rest of the data so I could just import that data into google thereby showing a sample flight path at any exit.