A blind encoder is an altimeter that encodes pressure altitude and outputs it on a databus. They are "blind" in that they do not display data to the pilot. Most general aviation units use a parallel bus with Gillham encoding. More expensive units and air data computers use serial bus output, commonly ARINC 429.
Historically, the blind encoder existed to ...
RAIM (Receiver Autonomous Integrity Monitoring) is a function within an avaition GPS receiver. It uses redundant measurements for a consistency check to determine the intergrity of the position measurement.
Since RAIM requires redundant measurements, it is only available when there are sufficient measurement sources available. In practice, this mainly ...
The website that Ralgha points out is indeed the one to look at for the US. They also provide a SOAP interface should you want to create your own app for the IPAD.
For RAIM to be available, you need to check firstly that at least 5 satellites (Space Vehicles in GPS language) are visible from you position, or 4 if your RAIM algorithm uses Baro-aiding. They ...
The FAA website predicts pre-flight whether RAIM will be available
The RAIM algorithm will tell you during your flight if GPS is working correctly.
The pre-flight FAA website check is not a substitute for the use of the RAIM function during flight. It will only show whether the RAIM function is available during flight.
RAIM stands for Receiver ...
Answer lies on AIM 5-1-16 "rnav and RNP operations" paragraph f:
f. During the pre−flight planning phase RAIM prediction must be
performed if TSO−C129() equipment is used to solely satisfy the RNAV
and RNP requirement [...] Operators may satisfy the predictive RAIM
requirement through any one of the following methods: [...] 2.
Operators may use ...
Details of RAIM calculation is explained in the paper :
GPS EASY Suite II: easy13 - RAIM by Kai Borre
Also the author gives a Matlab implementation.
Hope it helps.
RAIM availability calculations are simply checking to see if at least 5 satellites will be visible, that's all it is. You'll need the orbital equations to calculate that though. It would probably be easier to pull data from one of the websites that provide RAIM information. http://www.raimprediction.net is the FAA's site.