Few possible routes - given several Inmarsat arcs
 

@awblain
RichardC10 has posted that he has used computer simulation to determine that if a set of several Inmarsat arcs is available then if a constant course is assumed then two unique track can be obtained - one for each hemisphere.

http://www.pprune.org/rumours-news/5...ml#post8386704

says:
I have the impression that Mr RichardC10 is cluefull.

In my view the whole post is worth a careful read.

BOACthey had a track but were not certain it was 370, they tracked it to the straits of malacca until losing contact.

The fact that it was 370 was confirmed at a mid week conference by the minister based on a variety of data, so your sleepy byes argument is like most of your argument -rubbish

It is not easy to measure altitude of plane by radar. If I remember times of my military service, the main lobe of parabolic antenna is not narrow enough to measure altitude with good accuracy. To increase accuracy, vertical orange peel antenna was used, but I can remember that a precision was not usually better then +/- 3000 ft. Sometime worse, it depends on distance between plane and radar, clouds, surface objects, size of plane etc.

http://upload.wikimedia.org/wikipedi...a/Mps-16-1.jpg

To track position of plane like T7 at FL 300+ and distance about 200nm was very easy. Blips were clear and you could see them in a second on the screen.

Inmarsat

I understand that the arcs are based on the time difference between TX and RX of the signal from the satellite. Would such a signal frequency experience doppler shift if the aircraft was travelling towards or away from the satellite?

The other inference of the aircraft ACARS responding to the satellite is that there must have been power on that particular bus.

Confused?
 

BOAC:
What is the basis of your assertion concerning what Inmarsat has said? I don't believe I've seen any such statement. Have I missed something?

MB, Its the intersection of two spherical surfaces. One being the earths surface the other being the locus of all points a certain distance from the satellite based on signal travel time.

MB - I don't think you understand the 40 degree elevation actually. Work out please (someone did it way back here) what difference a 6nm change in altitude would make in angular terms over a distance of 22000nm +? Un-measurable, I suggest. Altitude has very little to do with it. The 'red arcs' are probably drawn as ground position but would be near as dammit the same at 40,000' - a 3-D 'corridor' if you like.

No! Only the final 8:11 ping came from a position somewhere on that arc, that's all.

- ah - confirmed??? That's alright then. That would probably be the same minister who has changed tack just a few times?

I remain totally unconvinced so far of any 'stated facts' - except LKP and the 'essence' of the Inmarsat man's words. Everything else is 'subject to'. You, of course, are entiltled to believe all statements from Malaysia.

Surely there are. Off the top of my head, hijacker(s) with threat or use of force.

The terminal probably has to correct for doppler shift, because low bit-rate channels are very narrow; doesn't take much of a frequency shift to end up transmitting on or listening to an adjacent channel. There's a lot more flexibility in timing, which presumably explains why it doesn't try to correct for that.

The 40 degree "arc" has nothing to do with the plane's altitude.

If you plot a great circle map centered on the sub-satellite point, the 40 degree "arc" will be a circle.

Anywhere along that circle, the satellite will be 40deg elevation.

As the satellite is just under 35800 miles above the earths surface, the altitude of the plane will make a small difference to the elevation angle, and the effective circle under the plane on the surface would be marginally smaller than the 40deg circle on the ground.

Another way to look at the "arc" or circle, if you draw an imaginaru line from the sub-satellite point, through the satellite, and out into space, then positioned your self on that line far out past the satellite, then looked back at the earth with the satellite in the middle, the 40 degree "arc" would appear to be a circle, and the circles would get smaller until at 90deg, it is just a point.

Let's get something straight. The arc that we are presented with has nothing to do with 40 degrees except it happens to be a 40 degree arc. And it has nothing to do with the path of the aircraft.

The arc is simply a line that marks the potential range of positions of the aircraft at a single, specific moment in time, based on a single ping from the satellite. It is the distance from the satellite computed based on the length of time from the time at which the satellite sends the ping until it receives the response. The aircraft's altitude would have very little effect on the position of the line... perhaps a couple of miles, but there is enough potential error that the altitude makes very little difference

The Inmarsat satellite does not have any azimuth information. The data that we are being presented with is simply a distance from the satellite at the moment of the last single ping. A radar works sort of the same way... the time it takes for the signal to return to the radar head determines the distance. The difference between radar and this type of information is that radar provides the azimuth (direction) of the signal based on the direction the radar antenna is facing at the moment the signal is received. RADAR stands for RAdio Direction And Ranging. All this satellite can provide is RANGE and that's all the arc represents.

Thank goodness they didn't present the arcs from the other pings. It would have been even more confusing.

Zorin - you cannot dispute that the start (0111??) and finish (0811) were around that arc? Has the elevation for the intermediate pings been published?

I take it that the search planes can fly in the dark !......So why take off at first light. If it takes 2 hrs to get onsite couldn't they leave 2 hours earlier ??


Sorry, I didn't get that the time change would be so great. I had guessed about 1 hour......seems I was wrong

I don't understand why they released information about the final "handshake" but not the others.

It would have made sense not to have revealed information about any of them for security reasons maybe, but once they released information about the 8:11 handshake it seems odd that they didn't do the same for the others.

- had to chuckle there - that lightened up a heavy day!:)

Chinese Satellite Objects Not Sighted By Aircraft
 

AMSA reports not sighting objects spotted by Chinese satellite. [Update#10]

"This evening China provided a satellite image to Australia possibly showing a 22.5 metre floating object in the southern Indian Ocean. AMSA has plotted the position and it falls within Saturday’s search area. The object was not sighted on Saturday.

AMSA will take this information into account in tomorrow’s search plans. "

Most likely the objects have floated away.


http://i58.tinypic.com/witvkw.jpg

ocean currents
 

Unlike the tidal currents for example in the north sea which are well known and predictable but always subject to variation such as due to weather. Ocean currents can only be predicted in terms of a long term average drift because there are rotational patterns which move generally in the direction of average drift. Consequentially the drift experienced on a particular day may be in any direction even counter to the long term average drift. This in no way can be extrapolated to previous or subsequent days.

When the search planes first arrived on scene bouys were dropped which will provide very interesting information. How useful will depend on the position relationship to any debris. Hopefully there are a significant number of bouys deployed over a wide area.

What is interesting is the dispersal power of the sea, if you observe two items close to each other it is often amazing to watch them drift apart.

There are particular area of the world where debris accumulates, if this sad saga does continue for many years it may be worthwhile stationing vessels in these area to analyse what turns up.

The BBC had a supposed expert on who postulated that because there is new satellite image 75 miles SW of previous then there is a 1.8 knot drift over the whole period (he failed to use the term knot) fortunately they have just now found an oceanographer who has strongly disputed this.

Rory

you must be the only person in the world who now does not accept they tracked MH 370 to the malacca straits. The minister quoted the data that allowed him to make that statement I just can't recall what it was, he wasn't telling us without evidence as you seem to imply.

Why do you think all the debate about did it go to the straits has stopped.