The place for technical discussions about GA and flying.
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By flyer5
#1858947
I would like an app that displays my GPS altitude minus the height of the ground, in other words giving a continuous QFE height. If that's not available, have you seen an app that gives ground elevation at the current latitude/longitude? In both cases obviously I would studiously try to avoid a constant cell connection.

I have had a look on the internet but it is very difficult to work out what relevant apps actually do - descriptions are very terse and often in confusing English. You also get the impression that most rely on a constant connection.
By TopCat
FLYER Club Member  FLYER Club Member
#1858951
Irv Lee wrote:Skydemon - just tap the altitude read out and it displays height (not everyone knows that....)

They do now!

I certainly didn't. That is pretty cool. Is it a toggle? ie tap again and it's back to Alt?

I only discovered recently that a long press on the zoom control returns it to the default scale, which enables me to count thumb-lengths again to get distance and time.
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By Irv Lee
FLYER Club Member  FLYER Club Member
#1858954
@TopCat Yes, reverts to altitude with another tap - like you can tap between ETA at destination and a few other things like ETE next, ETE end, or distance end, or distance next point en route. I gave a club evening talk at Sherburn just before my last PPL Masterclass there (about 2 weeks before 1st lockdown) , LOTS of 'well I never knew that' from regular SD users in the club
By riverrock
FLYER Club Member  FLYER Club Member
#1859090
@flyer5 height accuracy can be quite variable, so be aware. GPS references its height to a Geoid, which may or may not be corrected by the device you're using to make it more accurate, before the height above sea level gets passed to an app. GPS is also fundamentally less accurate in height than latitude / longitude (there is a system to make it more reliable / accurate but EGNOS is no longer available in the UK). You then need a terrain map, which will vary on its resolution, and isn't going to include features such as trees or buildings. If you want to avoid transmission masts and wind farms, you then need an obstacle map.

There are systems that do all of this, but you wouldn't want to rely on it for any sort of finer details around terrain avoidance less than 500 feet.
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By GrahamB
FLYER Club Member  FLYER Club Member
#1859119
riverrock wrote: ..there is a system to make it more reliable / accurate but EGNOS is no longer available in the UK..


Sorry, but that is complete misinformation.

EGNOS is still up and running and available in the UK. The two RIM Stations located in the UK that provide the corrections for this region are still operating.

What has been been terminated is the UK's subscription to the system, which means the administrative safety wrapper which is required for certain applications, including LPV approaches, is no longer available to the UK.

There is currently a NOTAM which instructs pilots wishing to fly RNP approaches that they must now operate to minima other than LPV. I'm not sure if it's started happening yet, but progressively LPV coding and minima will start to disappear from RNP APCH capable navigators as the data providers are instructed by the CAA to remove them.

Your iPhone, Samsung, GPS495 and car SatNav etc. will continue to operate as before.
Last edited by GrahamB on Fri Jul 16, 2021 4:36 pm, edited 1 time in total.
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By GrahamB
FLYER Club Member  FLYER Club Member
#1859121
Paul_Sengupta wrote:
GrahamB wrote:Your iPhone, Samsung, and car SatNav etc...


Many of these don't have an SBAS receiver and even if they did you'd need a clear view of the sky to the south!


And many of them do, so in other words, they will all continue to operate as before.
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By rdfb
#1859128
TopCat wrote:I only discovered recently that a long press on the zoom control returns it to the default scale, which enables me to count thumb-lengths again to get distance and time.


Tip: the built-in ruler gives you distance and time. On an iPad, touch and hold two points and it'll tell you the distance between them, and the time (looks like it's based on your current speed and corrected for wind). It also gives you true and magnetic track in both directions (make sure you take the right direction with a quick gross error check). On Android, I think you have to touch and hold, choose the waypoint or location coordinates, "Measure from here", and then touch the second point.
By TopCat
FLYER Club Member  FLYER Club Member
#1859130
rdfb wrote:On Android, I think you have to touch and hold, choose the waypoint or location coordinates, "Measure from here", and then touch the second point.

Thanks - clever innit.