Position sensor for rotating axel. (Angle measuring Magnetometer)

I have some use for some position sensor for my Solar Tracker system. I need to know the Tilt-angle and the Rotation angle of my Solarpanels.

Description of my project.
http://www.thronborg.com/MadeByThronborg/solarpower-1.html

Theese little sensors, Allegro A1335 and Melexis MLX90393 is used in cars for controlling their ABS and ATC Tracking system as VOLVO so i think this is a really good sensor. I am suprised there are so little information about this angle sensor and little use by Arduino friends? And specially when they dont have any mechanically contact with the sensor it can get dirty and greasy without any problem and they are cheap and have high precision and you can buy them on Ebay or AliExpress.

Melexis MLX90393

Allegro A1335

Anyone that have tried theese or have any information or code examples?

Ole Sweden