some littles bugs I've noticed

[piwaille]

Hello every body,

I don't know exactly how you work in this group ... I just want to bring my very little help with this nice project. I can do some reports of my use.

I think that bug report are done in this forum ... so I will do this. If I'm wrong, please tell me the best way to help you.

So now that I've understood the way Gaggle works, I can make a report of the bugs I noticed in the flight I've made yesterday.

My phone is a HTC Evo 3D (don't know if you need some more details ? You'll ask me for if needed)

In flight instrument :

* I can't report many thing as I have my phone deep in my pocket. Any way, my screen is absolutly unreadable under the sun :/

* I was confused with the title of the button "debut d'enregistrement". I thought that it was a way for forcing record ... may search another text such as "début de surveillance" ? (or I may still wrong with the use of gaggle :S ;) ) as it just start

* I think the G sensor is not working fine : It recorded 1G max but I've done some spiral dive in english (3-6 in french ;) )... so even If I'm not very robust, it should be a little more than 1G ;)

Flight info

* start alt = 1591m, max alt =2706 ... It's wrong. My GPS noticed 1455 as start alt and ~2590 as max alt 

I can send you both IGC files .. all the more than looking at both IGC files, I noticed some littles differences in all coordinates. EG the take off is located 4523541N00606911E in my garmin and seems located around 4523545N00606915E in my phone (may be simply the error in GPS ? ) 

that's all by now. I've got a problem with leonardo's live track, but I think it's due to leonardo ... I will try to search time to contact them.

If it's really helping you, I may continue doing such reports

++

Piwaille

[sly (sylvain letuffe)]

Hi,

> I don't know exactly how you work in this group ... I just want to bring my
> very little help with this nice project. I can do some reports of my use.
> I think that bug report are done in this forum ... so I will do this. If
> I'm wrong, please tell me the best way to help you.

This list is more for discussion (maybe prior to reporting bugs) as bug
reports on this list tends to be forgotten or not well classified.

That's why it is better to report bugs here :
https://github.com/geeksville/Gaggle/issues

and _split your bugs_ reports one at a time.

Also, if there already is a similar bug report, try to improve the already
existing report in order to gather informations :
- On which device it occurs
- which gaggle version
- what circumstances, what function
- android version

> *In flight instrument :*

> * I can't report many thing as I have my phone deep in my pocket. Any way,
> my screen is absolutly unreadable under the sun :/

Same here, for us paragliders, most smartphone screens are close to unusable
in the direct sun light and wearing sun glasses does'nt improve that (not to
mention tactil screen doesn't work with gloves). That's why I'm also using
gaggle only for livetrack24 live recording, track recoding and direct leonardo
upload

> * I was confused with the title of the button "debut d'enregistrement". I
> thought that it was a way for forcing record ... may search another text
> such as "début de surveillance" ? (or I may still wrong with the use of
> gaggle :S ;) ) as it just start

With a longer text, it could be "début d'enregistrement conditionnel" (start
conditionnal recording) as it depends on the settings you choose for in flight
detection.
I choose values such as recording starts as soon as I press the button,
therefore, the translation is good for me ;-)

> *Flight info*

> * start alt = 1591m, max alt =2706 ... It's wrong. My GPS noticed 1455 as
> start alt and ~2590 as max alt

I do have an altitude shift as well, but it seams to occur in every
application I use not only gaggle. And strangely, the shift is constant,
letting me to suppose the gps precision is good, but only shifted by ~60m,
there might be something with geoid used of other altitude computation
related.

> that's all by now. I've got a problem with leonardo's live track, but I
> think it's due to leonardo ... I will try to search time to contact them.

I have a problem as well on the leonardo interface, a link to my flight goes to
a guest user and does focus on some weird point on earth. This started with
the new live track's interface. But other pilots, using other recording
software doesn't seams to have the problem, so it might be related to a change
in the leonardo's live track's protocol not upgraded on gaggle's side

--
sly (sylvain letuffe)

[Alan Birtles]

The altitude difference is probably sea level vs gps altitude, your GPS May be automatically adjusting

[piwaille]

Hello,

I don't understand the difference you make.

both GPS & Gaggle are calculating altitude thrue the WGS84 standards so -as far as I understand- they should display the same altitude (at approx 3-4 meters due to calculation errors)

[Alan Birtles]

Are you sure both gaggle and your gps are showing WGS84 altitudes? Most gps have an option to adjust the WGS84 altitude to AMSL altitudes. It may also be that gaggle is using the AMSL altitude. IIRC the difference between WGS84 and AMSL can be around 60m in some places

[piwaille]

I still not understand what you mean by "AMSL"

WGS84 is an équation that give the "numeric" AMSL by describing the elipsiod the represent Earth.

The "real AMSL" is not implemented in GPS. It would be much to complicated

some reading : http://www.esri.com/news/arcuser/0703/geoid1of3.html

Or (due my bad english), I may have not understand something ?

Byt he way, I had 

* 136m difference at take off (~1500m alt)

* 116m différence at max alt (~2600m alt)

* 20m at landing zone ( ~500m alt)

All this events happened in less than 3km distance 

[Alan Birtles]

Many GPS have a lookup table which has approximate differences between amsl and wgs84 which then allows them to convert wgs84 into amsl

[Ed]

That's interesting, do you have any further sources of information on this Alan?

Testing in my 10 meter AMSL garden just now my Garmin GPSMap 60 csx was reporting a fairly steady 24 meters altitude, Gaggle was reporting 94 meters altitude.

The numbers from GPSStatus software seemed to be constantly changing sometimes negative, sometimes positive altitude figures.

Is Gaggle actually using WGS84 I wonder, or some other datum?

I'll test again later when I've recharged. Also have a Galaxy Tab to try.

Regards,
Ed

[Tomislav Muic]

According to GPS status FAQ:
GPS does not report the height above the mean sea level, rather the
GPS system compares the height to the WGS84 reference ellipsoid which
may be above or below the actual sea level. In different parts of the
earth it can be off by more than 200 meters (depending on the mass
distribution of Earth). For example the geoid's surface around Florida
is above the mean sea level by a good 30-40 meters, which means that
standing on the shore would show you -30m as altitude. This is normal,
and not an error, and caused by the fact that the altitude is relative
to an artificial reference surface and not to the sea level. If you
are interested in this topic, I recommend to read Mean Sea Level, GPS,
and the Geoid.

And WGS84 data is exactly what should be expected by default when
grabbing data from sensor.
(if there is built in option to recalculate to AMSL on the fly good,
but without that you should expect WGS84 and then convert it or not as
needed)

I used WMS services to get terrain elevation data and I suppose that
there must be something similar for WGS84/AMSL difference. I'll try to
look it up later.

p.s.
Standard non-flight terrestrial use GPS might also employ trick to
snap you to DEM elevation at your current location.

--
Tomislav Muić

[Ed]

Thank you. DEM elevation?

[Tomislav Muic]

DEM - Digital elevation model - basically a georefenced grid contaning
elevation data for points in some area.

There are several datasets available containing

--
Tomislav Muić