On Tue, 22 Aug 2017 04:48:16 -0700, Bruce Hoult wrote:

On Tuesday, August 22, 2017 at 2:24:38 PM UTC+3, Martin Gregorie wrote:
On Mon, 21 Aug 2017 17:35:12 -0700, Bruce Hoult wrote:

Of interest to glider pilots is that this project managed to
successfully find and centre in thermals using only the data
available from a GPS: the 5m model glider carried a pressure-based
altimeter but got better results by using GPS altitude and ROC
calculated from it because that was a less noisy signal than the
pressure altimeter could provide.

That seems very strange and completely against the experience of
every glider pilot with both a GPS and a modern MEMS pressure sensor
based computerised vario.

Yes, I agree. All I know is what it says in the detailed description
published as NRL/FR/5712--15-10,272. It is marked as an unclassified
document.

This work was done in 2006/7: I know nothing about the quality of
electronic pressure sensors at that time and I don't recall any
description of how the pressure sensor was connected to the rest of the
system or anything about what, if any, filtering or smoothing was
applied to the pressure sensor. Nor, for that matter have I heard
anything about people using GPS altitude information as vario input for
our use. The sampling rate, at least, is similar to the response rate
of many electronic varios so that approach may work for us too.

You can find what looks like a full description he
https://www.dsiac.org/resources/jour...2016-volume-3-
number-2/pursuit-persistent-isr

or search on the document reference: the first search result identifies
the {PDF version that I have a private copy of but the site is either
dead or very slow indeed. If the above reference doesn't give enough
information you can contact me off-list: the copy I have is marked
unclassified.

When in extreme scratching situations, the pressure altitude from my
1994 Cambridge Aero Instruments "GPSNAV" (one of the first units, hired
to a competitor in the 1994 pre-Worlds in Omarama) has saved my bacon a
number of times by letting me know whether I'd gained three feet or lost
five feet in the last circle.

By 2006/7 something used in a military project should be excellent!

It wasn't military in 2006/7 - just the subject a PHD thesis written by a
student aeronautical engineer. I'd read reports about the project in
model flying publications such as the AMA's 'Model Flying' until its
developer graduated. At this point it seemed to go dark fairly rapidly.
My guess is that this was when the UAS surveillance crowd became aware of
it: most likely when the thesis was published. More info only appeared
several years later.

It seems reasonable to guess that the author was pretty well-known in RC
soaring circles because one of his aims, in which he succeeded, was to
have ALOFT accepted as a competitor in one of the Californian cross-
country soaring contests. These were multi-day events that routinely flew
tasks of up to 100 km with the pilots driven round the task in a
convertible or a beach lounger on the back of a pickup truck. ALOFT was
hand flown for launches and landings and autonomous the rest of the time
with the software running on a laptop with a bidirectional radio link to
the glider, an ARTF 5m soarer kit. The laptop and its owner also followed
the glider round the task by road along with the pilots of the other
models.

So, to me this means that the autopilot hardware was more likely to be
state of the art RC model gear rather than military kit.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
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