Thought users might be interested in my experience of SkyDemon during a trip this w/e.

Left Husthwaite (NY) Sat am, flew to Cromer (landed) flew onto Beccles (stayed over). Departed Cromer Sunday & flew to Weybourne (landed) took Off & went to N Coates and finally returned home around 5pm Sunday.

Comments areas follows. As previously, the features re vert nav, NOTAM warningss and clarity of maps are v good. Best in Class. BUT.....

1. The programme's auto-sensing of where you are on a route really does not work in a way that I find acceptable. I plumbed in a route that covered the whole trip. But when I started up at Beccles it informed my I was 140NM "off track". It therefore assumed I should have been back at my home airfield. No such problems with my G296 which made the correct assumption re where I was and what wd happen next. I should say it is indeed possible to "fool" the 296. If you have aroute that leaves and returns to home airfield with pretty similar legs and you start off on the reciprocal of your intended final leg, the 296 will automatically invert the whole plan! Does not happen often and I now know what to do about it.
2. This also mean that if ATC ask you to give estimate at next waypoint, you can't. Hopeless.
3. But SD's internal logic is simply not good enough for what I imagine is a pretty common usage. If you are just bimbling about you are not going to set up a route and plug into GPS.
4. The default offtrack alert is too senistive  .. being told I am 0.2NM off track is a pain.
5. Redrawing Map warning is simply annoying  .. cannot see why I need to be told at all  .. just get on and redraw asap.
6. Actual Time  .. not sure waht can be done about this one. The clock on my GPS (Navigon 8410) did not show the correct time in SD. If I loaded the normal Navigon program, then clock was correct (local time of course). And it was not just 1hr adrift to mean Zulu time. It was hours out.
7. As anothe 8410user has pointed out, sometimes it stops logging the track and re-fixes staellites. Works 100% in PFMS and in native Navigon. Feels like a snsitivity problem. I certainly do not want to have an external antenna  .. 8410 can get a fix indoors and so shd not drop the signal outside.

OVERALL

No way cd I use this unit as primary GPS even tho there is lots to like. Route logic is NBG. Drops signal too often. Some defaults need sorting but I know I can override.

FINALLY

How do I tell the unit I have a full license. Mobile Device Ctre does not work with 8410. Where do I put the license file? This also drove me nuts on 2 hr flight.

SD card sync  .. roll on this feature.

Of corse I write this not on the spirit ov overt criticism but in order to amke something that has huge potential to be basically usable in a real trip.

Cheers

David

Have been thinking about how garmin determines which leg you are "on" at any point in time and space.

From observation and use (not from discussion with garmin support), what I think happens is that it determines which leg you are least "offtrack" from and assumes this is the leg you are flying. For example if, as you approach a waypoint between two legs you cut the corner, even after you have passed abeam the waypoint, the Garmin will try to get you to head back to the waypoint. But as soon as the amount by which you are "off track" Leg 1 is more than you are "offtrack" from leg 2, the Garmin starts to give information about the next waypoint (time, distance, heading etc).

In the air this feels very logical and intuitive  .. but as noted previously you can still "fool" it.

Hope that helps a bit more.

David

David,

1. There is no "auto-sensing" of where you are on a route in SkyDemon. When you load a route that starts at Beccles and proceeds to Waypoint X, SkyDemon thinks you're on the course from Beccles to X until you pass X. End of story. You can inform it that you've passed X manually by tapping the "Next:" text or wait for SkyDemon to notice you've passed it and advance you automatically (which can be turned off). If you load a route that starts at Waypoint Y and then proceeds to Beccles, and you're sat at Beccles, then you will want to advance the next waypoint yourself.

2. No, it's not "hopeless". You need to know what SkyDemon does and doesn't do (documentation) with regards to advancing you automatically through your route.

3. I don't know what this point means. Seems to be related to your previous points.

4. SkyDemon doesn't consider you off track until you're off track by 3.0NM (the default which can be changed). Once you're off track it will consider you back on track when you get within half of this value (i.e. 1.5NM) of your course again. I suspect this warning might be related to SkyDemon thinking you're flying a different leg than the one you are actually flying (see point #1).

5. This doesn't slow down map redraw and removing it would be pointless. It was added due to lots of customer feedback.

6. The clock on your device is set wrong. SkyDemon doesn't currently automatically adjust your device's clock based on the GPS clock if it senses a discrepancy. Presumably the software you're comparing with does. We've had a few requests for this and the chances are we'll add it at some point, once we are sure it won't upset any SkyDemon internal metrics.

7. SkyDemon has nothing to do with your GPS signal. Software that makes use of GPS has zero involvement in acquisition of signal, that's up to your chipset. We just make use of the output.

Your feedback is greatly appreciated.

When you run the SkyDemon Mobile installer your license is automatically copied to your device (whether or not you use ActiveSync). If your license isn't on there, you haven't run the installer since getting your license.

You said "SD card sync.. roll on this feature". This feature has been available in the 1.4 beta since Saturday.

Tim

OK so "hopeless" was a bit harsh. I now see how you can advance to next wp. Even so I do feel the Garmin method is smarter.

Updating clock wd be very good.

Now I have 1.4 and no longer evaluation version, I will see re GPS logging etc.

David

As another Navigon 8410 user I thought I'd jump in.







That's right. The Navigon software sets the clock from the GPS signal, and that's the only way the clock is ever set on the device. The solution at the moment is to boot into the Navigon software occasionally.







Well, SkyDemon is actually involved here. As I've found myself, the software filters the signal being received by adding a DoP (dilution of precision) threshold: it chooses to ignore the GPS signal when the DoP exceeds this threshold because although it has a GPS location, the potential error on this location is too large (for SkyDemon's definition of 'large'). This will be why you observed a discrepancy in the ability to see your location between Pocket FMS and SkyDemon, even though you're using the same hardware. An external antenna solved the problem for me, but it's a 'problem' that was only created by the software.

I am intrigued by the Garmin's apparently way of determining which leg of your route you are "trying" to navigate. We'll definitely be giving this some more thought.

jsnr, you're quite right that we do apply some broad filtering to GPS input before passing the values to the navigation instruments. That's not to say that we have any input in signal acquisition or processing, but I can see how it would appear that way. We filter data because unless the chipset has a reasonable confidence that the values are correct, we don't think they are appropriate for aviation navigation.

Here's a rough breakdown of horizontal DoP values, which is what we use:

1-2: Excellent
2-5: Good
5-10: Moderate
10-20: Fair (low confidence level, very rough data)
Over 20: Poor (inaccurate, should be discarded)

At the moment we require a horizontal DoP of better than 15 for GPS data to be passed through to the instruments. We have considered (and are still considering) an option called "Require Precise Data" which could be turned OFF for all data to be passed through. This would result in "quicker" fixes but would always be opt-in.

Glad u r intrigued by Garmin's approach. As I say this is not definitive but my interpretation re what happens in practice.

Wd u like me to contact Garmin support and ask how they do in fact decide?

D

Well sure, couldn't hurt

Spoke to tech suppt at garmin who were very helpful. They confirm that the Garmin algorithm re  "current leg" looks for the leg from which you are "least offtrack" and presumes this to be the leg you are flying. AS I said you can therefore fool it by flying close to the anticpated final return leg when you depart (it then inverts the whole plan!).

Similarly they said if you finish somehwere fairly close to your departure point (but not the same point), then this can fool it too. Trick is to invert or reactivate the plan once you are on proper course.

In my view this is a far better logic than that currently used by SD.

Cheers

D

Thanks for following this up. I like the logic behind it, and it's something we'll play with in a future version of SkyDemon. Interesting idea, automatically reversing your trip, too.