PAW equivalent to the Foreflight Scout

[tnowak]

This looks a good concept:
https://www.ainonline.com/aviation-news/general-aviation/2017-07-18/foreflights-scout-adds-low-cost-ads-b-option
Any future plans for a PAW equivalent of this for aircraft already equipped with a Mode S transponder and ADS-B out capability?
I don't need the PAW transmit capability but would like to be able to receive ADS-B Out and PAW transmissions.
I wonder how difficult it would be for UAVionixs to modify their receiver to accept PAW transmit frequencies?

Tony

[Keithvinning]

Tony

PilotAware already does everything that this does.

Unlike more expensive ADS-B receivers, Scout does not include GPS, AHRS sensors or a barometric sensor, nor does it have the ability to record Track Logs. It is also not fitted with a battery, which means that it requires an external five-volt power supply, either from a portable battery or USB port installed in the aircraft.

Without a barometric sensor this is dangerous as one needs to know the local barometric pressure for accurate separation.

I don't need the PAW transmit capability but would like to be able to receive ADS-B Out and PAW transmissions.

Why don't you need a PAW transmit capability? Others with PAW will see you then?

PilotAware already does it all and more.

[Admin]

Hi Tony

the most important feature you will miss without PilotAware transmit, is the ability to receive OGN-R uplink for FLARM and OGN Trackers.

How is that I hear you say 

Well, the OGN-R uplink is triggered by receiving an interrogation from a passing PilotAware Transmission
The OGN-R Evaluates where the transmission was positioned, and calculates if any FLARM/OGN Aircraft are withiin your proximity.
If an aircraft IS in your vicinity, it sends a transmission back out with those aircraft positions, allowing you to see them on your tablet, and hear them in your intercom (if audio connected)

And regarding your question for uAvionix receiving PAW, that would be fine as a passive system listining to active broadcasts fro other PilotAware devices, but as above, would not trigger a response from an OGN-R uplink

Thx
Lee

[tnowak]

Keith/Lee,

Thanks for the replies.
Firstly, I have ADS-B out via my Trig Mode S transponder, so surely close-by PAW equipped aircraft will detect me?
Regarding the barometric sensor - are you saying that my GPS mouse, providing ADS-B out data, won't be providing sufficiently accurate height data for PAW only equipped aircraft?
The info about OGN is interesting as I wasn't sure how it really worked.
I wonder whether the OGN network will ever be enhanced to also detect ADS-B out transmissions? To me that sounds like a worthwhile system upgrade.

Regards

Tony

[JCurtis]

Firstly, I have ADS-B out via my Trig Mode S transponder, so surely close-by PAW equipped aircraft will detect me?

Correct, even fairly distant PAW equipped aircraft will be able to see you, as your Transponder ADS-B out is a decent RF power.

Regarding the barometric sensor - are you saying that my GPS mouse, providing ADS-B out data, won't be providing sufficiently accurate height data for PAW only equipped aircraft?

Assuming your mouse feeds your transponder, your mouse sends GPS Lat/Long/height to your transponder and I would hope the transponder would use it's own altimeter encoder to add in altitude when creating the ADS-B packet for transmission.  So the altitude is derived from a barometric sensor rather than GPS height.

The ForeFlight Scout receives ADS-B, so what is receives should have good altitude data* in it - but then depending on what it sends this data too if it doesn't have the same barometric altitude reference the different in relative height between two aircraft will be wrong.

What is needed is a common reference plane for altitude to calculate the relative difference between two aircraft, and that is barometric pressure at ISA 1013.  Remember altitude is with reference to 1013mb but height is with reference to a locally set QFE - they can be quite different.  GPS is neither of these but a calculated height above MSL and doesn't take into account the change in pressure with temperature - this, whilst for gliding, gives some insight into the difference http://www.borgeltinstruments.com/GPSvsPressurealtitude.pdf

* Side note: The ADS-B protocol caters for both the pressure altitude and GPS altitude in the data stream, position data Type Code 9-18 with barometric altitude and 23-31 with GPS height.  It might be an interesting exercise for someone to receive both and see what the different reported actually is...

[PaulSS]

It's a £150 ADSB receiver, without GPS. Why would you want to pay more for something that does less than PAW, to which you also have to input a GPS signal?

As you say, you've got ADSB Out, so a PAW user would be able to see you without using the PAW signal. There are other PAW functions that you might want to use (the group callsign option, for instance) but, if not, does it do any harm to transmit over the PAW frequency? The Scout only receives ADSB, so no function for Mode C/S.....and it only seems to link to the Foreflight navigation app, so no Sky Demon etc.

I'm struggling to see what the advantage is of the Scout over PAW.

[Admin]

Hi Jeremy,

* Side note: The ADS-B protocol caters for both the pressure altitude and GPS altitude in the data stream, position data Type Code 9-18 with barometric altitude and 23-31 with GPS height.  It might be an interesting exercise for someone to receive both and see what the different reported actually is...

Did this exercise a long time ago, and of course it depends upon the Pressure on the particular day.
More importantly, I found that a tiny tiny minority transmitted the GPS Altitude, it was less than 1%
whereas all transmit the Pressure altitude.

Thx
Lee

[Admin]

.....and it only seems to link to the Foreflight navigation app, so no Sky Demon etc.

Hmm, I would be surprised if it does not link to SkyDemon, I would have thought they are using GDL90, which SkyDemon supports.
As you say, Mode-S/C (unsupported under GDL90), OGN-R, Audio ...

Thx
Lee

[tnowak]

PaulSS,

I do not have a traditional electrical system in my vintage aeroplane so rely on a (removable) 4.5AH NiMh rechargeable battery.
This battery, when fully charged, gives me around 8 flying hours of power for my radio, Trig TT21 transponder and GPS mouse for ADS-B out.

PAW is quite power hungry (12W?) and will significantly reduce the available battery capacity by around half.
Yes, I can purchase a standalone battery for PAW but that adds weight and the need for another charger, if I am touring.
I am also try to keep carried weight down - it all adds up when touring!

The Scout would appear to do some of what PAW does in it's "receive mode", but would obviously need modified code (and RF reprogramming?) for it to work with PAW transmissions
I wonder what would be involved in getting the Scout code modified for compatibility with PAW?
The Scout also appears to be truly "plug and Play". Just power it up and stick it to one's canopy??? I am sure it can't be that easy....
Just seemed to me that the Scout is using advanced build/processing technology and perhaps is the future?
Tony

[PaulSS]

Sorry, but I still don't understand what you're trying to achieve 

You said, "I wonder what would be involved in getting the Scout code modified for compatibility with PAW?" To do what?

All you're getting from the Scout is ADSB In and you're paying more for it than PAW, that does a lot more. Why would the PAW guys want to make it compatible when there's already an ADSB dongle on the PAW that does exactly what the Scout does i.e. receives ADSB?

With the PAW you could get rid of your GPS mouse, if you wished, as the PAW GPS will enable you to have ADSB Out from your TT21.

I've got a battery pack that is suitable for the PAW and it weighs 117gms, so I don't really think weight is an issue. I can charge that battery from any USB outlet with a single cable, so no mucking around with chargers.

If I was going to be a real smart-arse I might recommend something like the EarthX ETX18B battery. 6.2Ah and it weighs 1kg......enough for quite a few PAW batteries if you've got a normal lead acid battery that weighs as much as gold.

I don't know about 'advanced build/processing technology'. The Scout is an ADSB receiver, with no GPS but it does have a sucker cup. The PAW is a little bigger but has Mode C and Mode S, ADSB, PAW in/out, a GPS, links to OGN (and hopefully more to come in the future) and costs less than the Scout. No sucker cup though 

I know I might sound facetious but what is it that you think the Scout would be capable of if the boffins at PAW were able to make it compatible?

[Admin]

Hi Tony, Paul

I think the bigger issue is that this device does not have a barometric pressure sensor.
the vast majority of ADS-B transmissions (and certainly GA Mode-S/ES) use a barometric encoded altitude
https://flywithscout.com/
Scroll down to Scout vs Stratus Comparison, distinctly lacking in features
- no GPS
- no Barometric Sensor
- no Flight Data Recorder

and you still need an external battery!

With no sensor on-board this is unable to tell the relative height, only the absolute height of any traffic
in which case the NAVIGATION device has the following information

Your height measured in GPS
Their height measured as pressure altitude against 1013mb

these are not equivalent, and in fact the first SkyEcho devices made this very same mistake and had to be recalled and replaced by devices containing a barometric sensor. So I have no clue why they are now pushing another device which has no sensor

On days with varying high/low pressure reported altitudes will be vastly different.
It could report traffic above when it is below, and traffic below when it is above.
This is not a good approach, I am unclear who the target market is.

Thx
Lee