REFLECTOR: GPS outage, no big deal

[Mark Magee]

On Dec 2, 2012, at 4:27 PM, Scott Derrick <scott at tnstaafl.net> wrote:

> Mark,
>     I don't know what GR's INAV is, it's certainly not real Inertial Navigation!

As I understand it Grand Rapids, and hopefully others have -Electronic- INAV: which is very accurate digital accelerometers on 3 axes that give better accuracy than the old mechanical accelerometers coupled to spinning gyros. Basically the AHRS that GR sells (I don't have one, and won't sell you one) is a stand alone box that if told where on earth it is, will calculate from 3 axis digital accelerometer data where on a 3D plane you move to; no external reference. It does cross check to GPS. As well you can install two of them for redundancy and they as we'll will cross check each other.
GR sells this AHRS to the military and others for a wide array of applications (hopefully not the Iranians!).
Basically you get better accuracy for around $2,500 USD as to what used to cost the Navy 1MM each for the Submarine fleet. I knew the engineer at NASA that owned the INAV package on the Space Shuttle fleet, he had a team of 6? folks whose full time job was to maintain the 3 INAV boxes in each Orbiter. This was mid 1980's, he said each box was 1MM USD's (x3 for each bird). I had buddies that served on subs that had the same boxes, they said they would submerge off Point Loma (San Diego) and be submerged for 6 weeks. After 6 weeks of sub-surface maneuvering they would surface and take a Celestial shot and would normally be within 100 feet or less from where the INAV package said they were. That was 3MM USD's technology and a dedicated team of technicians to maintain. We can now get better data for around $2,500 USD's each. So buy two for cross checking and redundancy and if Uncle Sam wants to jam my NAV (GPS), to Hell with him: 

Damn The Torpedoes an Full Speed Ahead! 

I don't have to have your GPS inputs! My precious little boxes have all the data I need to get where I'm going, no external data required.

Jam my NAV signal? In flight?
I told you guys I am an activist on this. 

Scott, it is -better- than what we used to term -real- INAV. For fractions of a penny on the dollar.


Mark B. Magee
N34XL
Sent from IPhone 4S