Raim/rnp/anp

[Spooky 2]

Was watching a Boeing produced CBT the other day and the statement was made in this lesson that Boeing/Honeywell "blend" the RAIM into the RNP/ANP data. Sorry but I don't see any relationship between these two items and if someone here has any idea how this statment could be true, please share your thoughts.

Anybody?

[Hand Solo]

There's no relationship between RAIM and RNP, but I suppose RAIM could be integrated into ANP. ANP is not an absolute measure of the aircrafts position error but a mathematical prediction of how large the position error may be. If RAIM is not available then the ANP could be increased to account for that.

[keith smith]

Receiver Autominous Integrity Monitoring is an airborne technique for evaluating how good the received data is. GPS needs a minimum of four satellites in electronic view at any time in order to obtain a unique position solution ( three position coordinates plus time). More than four in view, and theoretically you can tell that something is amiss if you don't get the same position solution from all possible four- satellite solutions. Trouble is that the accuracy of predicting the errors depends on the geometry of the satellites and more importantly on the number of satellites in the total constellation, and with GPS at about26 satellites, at times it is not much use. According to the experts, results would be somewhat improved with even the few GLONASS satellites, and greatly with a fullset of Galileo (if and when it comes to pass).
The maths is complex and there are different ways of implementing it. Stanford University are the prime Geeks in this area. There are several paers on the web. Iam reasonably technical, but I have difficulty understanding the technicality fine print.

[ssg]

http://64.233.167.104/search?q=cache:u3GRnNwZA8IJ:www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/0/cfdc5da6c7fb51dc862570a0006059ef/%24FILE/AC120-86.pdf+raim+rnp+blend&hl=en&ct=clnk&cd=6&gl=us

You could check this out...I gather RAIM might be used as an added surveilance measure to maintian RNP

[galaxy flyer]

Keith:

One issue with GLONASS is that the Russians do not use WGS 84 or EGM 96 for a datum. Some means of converting the Russian signals to WGS 84 must be installed.

[point8six]

Try Wikipedia for a write-up on GPS, which is an integral part of FANS 1/A, as is RNP/ANP. Currently, there are (apparently) 30 satellites in the GPS constellation, of which 21 are guaranteed to be operational. RAIM is required to check GPS errors.
Don't expect Galileo to be operational for a few years yet. GLONASS has only just been cleared for use by Russian Federation Civil use.
China also is not WGS84 compliant (can lead to "map shift" if GPS is the only update to FMC position).

[keith smith]

I don't think the different coordinate system of GLONASS is a great problem--it is "only" some geometric transformation arithmetic. Since I am told you can do all theGPS maths on a single chip these days, so what is a little bit more!
What is probably a greater difference between the two systems is the signal structure.Civil GPS (so far) uses single carrier frequency with multiple digital moduation (pseudo-random-numbers) adequate for all the constellation,(this is clever stuff invented by a guy called Gold). On other hand GLONASS has different carrier frequency for each satellite.
I think I have read somewhere that at leas one US manufacturer is developing a combined receiver

[reynoldsno1]

The Chinese CAA have given a tacit nod to adopting WGS84....:)