Can anyone suggest how to accurately measure the height of your jumps?
For example: some sort of GPS watch that takes readings continuously and calculates precise height or maybe a land based computerised theodolite or tracking dumpy level.
Any other ideas?
GPS are not accurate for height measurements unless you go to survey accurate differential GPS and a base station. Expect to spend about $100k.
There is an accelerometer based systems called Shadowbox that might be accurate.
You could wear a vest with a grid pattern on it. Take a video of your jump and count the number of pixels in the grid then project the line down to the water and count the number of pixels. Maybe add in a gps for a distance measure and do a bit of trigonometry.
Good Question
Ive asked it before with no response, but my research informs me that gps hight is inaccurate but a devise that can measure properly wound be one that measures air pressure.
So if you can find a waterproof gps that measures and logs hight with air pressure let me know by PM and Ill buy you a carton
Would have to log I think as it could be dangerous watching a digital dipslay from 40 feet up
Shadowbox might be the one as the video says it measures pressure but cant find where to buy, anyone know? Also a bit pricey.
Suunto watch says it has a altimeter and logging, might do it at at half the price.
Thanks for the info guys.
A bit of trigonometry might be able to help you. Won't get super accurate results though unless you're boosting dead vertical.
Completely separate from your kite at the apex of your jump, and freefall to the water.
Time it with a stopwatch
9.8m/s/s
There u have it.
... measure by how big your eyes get!
Rectal Pressure guage, measure how much you clinch in psi 
Count how many times you say sh!t and if you say "f@ck me" at the apex, its a good one
Not really scienctific but I thought I'd just throw it out there 
glue one of those surveyor's sensors to your helmet and get a surveyor to fire his laser at it from the beach.
Easy.
It's called the Variometer (BRAUNIGER, FLYTEC, etc.)
It's signalling with the high pitched sound when you go up, low signal for down, m/s going up/down, and all details of your flight to your PC after.
Being a paraglider pilot helps:) Beware, the device will scream on your awesome jumps:) You can switch off the sound tho.
Expensive version:
Or for about $200:
A vario will work ok inside a waterproof bag (because the pressure inside and outside is the same).
I would be astounded if a vario could give an accurate height reading over 5-10 metres in 5-10 seconds.
BTW. I sometimes carry a GPS when doing coast runs on my raceboards. Last time I looked it recorded a height gain of 196 metres! I'm good but not that good! 
I think an accelerometer system would be the best. Maybe you could write an iPhone app that uses the accelerometer in the phone.
The laser thing would be cool. You could make it like a video game. You could charge people on the beach to shoot at you and have some special effects explosions when they score a hit.
For the accuracy required and range of movement you couldn't go past laser.
Laser rangefinders like the below could be used from the beach pointing at the rider and their in-built tilt sensor calculates the geometry for you on the fly.
www.lasertech.com/Laser-Measure-Elevation.aspx
Best solution would be a laser rangefinder on your board/bar pointing straight down but I don't think there's anything available that's up to the task...
You could use the "guess" method, you do the jump and guess how high!
Then double it when you tell yer mates.
Yeah. I just past my mate. If I am looking down on his kite then I am fricking high!
The other fun way to gauge height is to do a long, high jump ... then watch all the windsurfers riding under your arc. My best is a three windsurfer jump. 
I like to jump over my mate's kite, haven't cleared it yet so I am definately jumping less than 25 meter high .
Since he got ****ty the last 3 times I cannoned into his rigg, I am giving him a month to cool down then we are on again.
Seems there is a 3D TRACKING SYSTEM that I know absolutely nothing about but Red Bull used for the inaugural "Red Bull Rockets" at Pozo Izquierdo, in Gran Canaria a year or so ago??
The 'Red Bull Rockets' apparently brought sixteen top national and international riders to see who can get the biggest jump (windsurfing)
What determines the BIGGEST JUMP is a real time 3D trajectory and measurement system. This revolutionary concept, designed by Epicsessions.tv, takes technology to a new level allowing data transmission, in real time. Each rider carries an electronic device in (I think they meant 'on'!) the arm during the competition.
Ok so the above is a cut and paste of the "event" but there is a Youtube vid which I cant find ATM ?? which kind of shows how it all works - extremely impressive. And holy moly they went big - very impressive!!the Pozo Vid is suggesting 11m as the best but the one I saw was able to show the trajectory of the jump, and its height - and from memory they were hitting nearly 60 feet (Hawaii?) . Ok small by kiteing standards but if you have ever jumped a sailboard - 10M plus takes balls!!
Perhaps the Kite community should invite Red Bull to a jump comp between the best kiters and poleys?? Amazing Technology - can anyone out there find the vid of the comp - very cool!!
Could you get someone to take a picture and scale it from you're size ?
Just a thought
I tested my vario and it is accurate to +/- 1m and takes about 5 seconds to update.
I zeroed it on the floor of my house. Lifted it to waist height and it would waver between 0 and 1m. Above my head it wavered between 1 and 2m before settling on 2m. At the top of the stairs it read 3m.
So, it's pretty accurate and more than accurate enough for flying. Nowhere near accurate enough to measure a kite jump unless you get to the top and hover there for 5-10 seconds.
I have a waterproof GPS with barometric altimeter in it. I might give it a try.
Jump next to a beacon with a texter in your hand and mark the level on it. Then go back and measure it.
