Hi
my name is Felix and im very new into this hole programming and Arduino(and Raspberry Pi) stuff.
First of all english is not my native language so pls dont blame me for any mistakes.
Please just ask if anything is unclear 
I got a little arduino starter kit long time ago and i ever wanted to learn at least some basics in c++ java or python but it never came that far until i got a cool idea (I hope it is one..)
So my idea is that Im gonna build a little waterproof gps tracker for my kiteboard (Wikipedia) that tells me later how fast i was and how high Ive jumped.
Actually there a two devices I could buy for 200 bucks each that tells me only one of that values. But then Ive learned nothing..
- A GPS watch that records speed and saves the max value
- An Accleration sensor that you can stick on a board and that records your jumphight. Via a smartphone an app and bluetooth you get acces to these datas
So I looked up the accuraty of GPS.
I think it was 2-5m accurate if u dont use a second method at the same time (thats how I understood it) or you dont use GPS but other satelites that are for military purposes only (which wont be an option I guess)
My question is how accurate a GPSchip for arduino will be AND in which way these values are inaccurate. I only need relative values so does it even matter if its 5m or 10cm? Which GPSchip should I buy or how much would one cost that is good enough for my project or should i use an accleration sensor?
The next thing I want to know is how hard the programming will be. As I said im at the very beginning so I really dont have a clue how much knowledge is needed.
In the book Im reading right now Arduino by Mark Schmidt (german) it says that only a very small amount of projects come across with only an arduino uno. I could image that I use my arduino to collect the datas and the raspberry pi (2 ithink with a piface digital element14 adition)
Or is there a rule about which and how many controllers or computers i need for a project like this?
After the programming stuff there is another problem. The power suply. I guess Im going best with one or two 9v batteries. But how can I calculate how long the device is gonna run.
On some other projects with arduino there was a lifespan for a very simple programm like 18 hours I think but I will definitly have much more power consumtion.
So how do I save everything and shut the raspberyy pi down(in case Im gonna need it) just right before the bateris are too low and I lose all my datas?
Ofc all of that got to be pretty waterresist. A friend of my dad got a good 3d printer. I never knew if its very hard to use and if the materials are strong enough for some crashes on water. I wanted to "print" a case which i can mount with two screws in the middle of my board where normaly a handle is.
Important to know is that my board is relatively unflexable but it still twist and rams(?) the whole time surfing.
So I need some shock absorbtation.
If I got all that I need to use that datas and values to make an graph for my hight and speed with one interval of maybe 50 ms (so I get the max hight) is there maybe a tool from google that reads the data and draws my paths on a geo map? That would be really cool.
So many questions and I know some of them are maybe here in this forum and others are hard to tell but i wanted to give you a complete overview about my ideas and problems.
If you understood those I would be very very thankfuly if you could tell me first if this is doable for me or if i should start with and hydration indicator for my cactus or sth else 
Second if you got any idea or solution for my problems that would be really cool
I hope this long text wasnt too tiring to read :S