SkyDemonLight & airways inaccuracies ?

[tdbristol]

I am looking at part of a route at 5,000' which includes:
- Cosford EGWC direct to Sherburn EGCJ

The new edition CAA southern 1/2 mil chart shows this to be OCAS as the Daventry CTA (Class A) starts at 5,500' along this track, except north-east of Sheffield where going into the Doncaster-Sheffield CTA [4,500'].

However, for this track, SkyDemonLight shows an infringement 10nm / hdg 338 from TNT, stating that M605 airway starts at 4,500' - the route above crosses the south-east corner of this airway. M605 as shown by SkyDemonLight does not coincide with nearby CTAs - SkyDemonLight shows the south-east corner of the M605 airway rectangle going into the East Midlands 5,500' CTA area, and therefore the track crosses this.

But, M605 is not shown on the CAA chart (at least, not that I can see, in this area at least - not sure about elsewhere).
Likewise, there are low sections of airways L8 [from 5,500'] and L10 [from 4,500'] to the north and east of Cosford respectively which are depicted by SkyDemonLight [and are shown as outside the nearby CTAs], but these areas outside the CTAs are also not shown on the CAA 1/2 mil chart.

I would have thought that SkyDemonLight ought to be fully accurate, as it is promoted by NATS, but if so, why are these areas not shown on the current CAA Southern edition 37 (2011) chart? (And there are no amendments listed to cover this.)

This would suggest to me that the areas of M605 in reality do coincide with the nearby CTA and that SkyDemonLight is not in fact accurate in its depiction of airways?

Any suggestions?

[BackPacker]

I have been mapping the M608 on a 2-year old Jeppesen chart I have here. If you just consider the centerline of M608 then M608 is fully contained within the Daventry CTA in that area so there's no need for a separate mapping. The map just shows the Daventry CTA with its lower limits and that should be good enough to remain free of M608.

If you want to map it yourself, here's the info from the UK AIP (ENR 3.1)
- From VOR POL to 533328N 0020149W lower limit 3500'
- From 533328N 0020149W to 531050N 0015303W lower limit 4500'
- From 531050N 0015303W to 530345N 0015021W (abeam TNT VOR) lower limit 5500'. This is the leg that seems to cross your route.

However...

The M608 is apparently 10 nm wide (according to the AIP). And if you consider the bit from 533328N 0020149W to 531050N 0015303W (second leg that I wrote down) and extend that laterally 5 miles either side, then the southeastern corner of that leg actually extends laterally outwards from the Daventry CTA at 4500' and actually infringes your route. This will probably be the bit that SkyDemon complains about.

Now to be honest I have no idea about the rules here. It looks like M608 is cutting the corner a bit but as you have noticed, this is apparently not mapped. But since SkyDemon gets its data directly from the AIP, it notices.

I couldn't find any regulations with regards to airspace priority in conjunction with the width of lower airspace routes in the AIP. Perhaps somebody else?

Anyway, the MSA in that area is 3300 feet so I wouldn't worry too much about it and just fly a bit lower. And just west of the TNT VOR (east of Stoke-on-Trent) you would be getting too close for comfort to the Daventry CTA anyway at 5000'.

[eharding]

Has the OP compared both SDL and the current NATS chart against AIP ENR 3-1-1-4 (version 7 Apr 11)? - therein lies the definition, there exists the possibility that one or other charts doesn't reflect the latest AIP.

[Tupperware Pilot]

Slightly off topic, what is "Wallis International" is shown on skydemonLite just East of Peterborough. Never heard of it, and cant find anything on google earth?????

[thing]

Also Walkington, just east of Hull appears to be in the North Sea. There are quite a few Norfolk towns perilously close to being awash as well. I wonder if the towns overlay is skewiff?

[JOE-FBS]

I cannot comment on the airways question but the positioning of features close to the coast has been mentioned in the other place. Apparently, it's something to do with the graphics and not an error, SDL does "know" correctly where these places are.

This long thread:

FLYER Forums • View topic - SkyDemon and NATS launch free pre-flight planning tool (http://forums.flyer.co.uk/viewtopic.php?f=1&t=69589)

[MFC_Fly]

Slightly off topic, what is "Wallis International" is shown on skydemonLite just East of Peterborough. Never heard of it, and cant find anything on google earth?????

You're not looking hard enough then :)

It is a grass strip just north of Whittlesey. Head out of Whittlesey on the B1040 to North Side. Just across the bridge over the dyke, on the right is a grass strip that runs parallel to the dyke. If you zoom in you will see there is a hangar in the back garden of the house with a swimming pool!

Also Walkington, just east of Hull appears to be in the North Sea. There are quite a few Norfolk towns perilously close to being awash as well. I wonder if the towns overlay is skewiff?

Unfortunately the data source that SkyDemon seem to use for it's towns and villages does not seem t be the best (by far!). There are many, many populations centres that are not in the correct place! This has been mentioned by several on the SkyDemon forum for some time, but as yet has still not been put right :{

MFC

[tdbristol]

Interesting; ENR 3-1 of 7 Apr 2011 does seem to correspond with SkyDemonLight for M605.

But I guess I had always assumed that
- if you have the current CAA chart
- and with the amendments
and followed the information carefully then you would be 'OK' in not infringing controlled airspace.

If indeed M605 has changed, then why would the CAA not mention an amendment to the edition 37 chart?
Avoiding the corner of M605 is not a problem on the given route, but there are lots of other areas of airways on SkyDemon which are not shown on the current CAA chart.
This would imply that one would have to do a SkyDemon check before each flight as well as looking at the chart, plus maybe do a print-out / screen grab of SkyDemon as well.
It would also suggest that one would take the SkyDemon print-out as the 'master reference' instead of the current CAA chart - which would seem counter-intuitive, complex and goes against what has been done for a long time (and I would have thought a lot of pilots would not do this).

[TC_LTN]

there are lots of other areas of airways on SkyDemon which are not shown on the current CAA chart

Could you list them? These need pointing out to the people that produce the 1/2 and 1/4 mil charts as a matter of urgency IMHO

[soaringhigh650]

I would have thought that SkyDemonLight ought to be fully accurate

I had a look at this thing. Type in a planned route of 12,000 feet. The airways are depicted much more complex than needed. It's easier to use the CAA chart instead.

[tdbristol]

Quote:
there are lots of other areas of airways on SkyDemon which are not shown on the current CAA chart
Could you list them? These need pointing out to the people that produce the 1/2 and 1/4 mil charts as a matter of urgency IMHO

I don't think I can list them all - it would require lots of plotting of different routes, perhaps at different heights, but there seem to be quite a few on quick looking.
I have looked a fair mount at the route I plotted (EGWC Cosford to EGCJ Sherburn at 5,000') and there seem to be 4 on this alone:
- L10 just south of the route near Cosford from 4,500' [v. small part]
- L8 north of the route, ~10nm north of Cosford
- M605 from 4,500', starting ~10nm on ~hdg 340 from TNT: the route infringes this
- L603 just to the west of the route partly coinciding with L975

In each case it seems that these are small corners or parts of the Class A airways that are near but just outside other CAS shown.
Anyone who knows better please correct me, but my reading of the ANO seems to indicate that all these airways are on a centreline then with a width of +/- 5nm. It seems to me that if you take the centreline alone it is within other CAS, but if you take the full 10nm width then parts of the full width lie outside other CAS.

My own guess at interpretation as to why these are not on the CAA chart [a complete guess! I may well be wrong] is that:
a) if the CAA were to add all these into the chart it would make it horrendously complex (or more so than it is already)
b) and aircraft in CAS would generally follow the centreline so are covered by other CAS [or would be otherwise in CAS]
c) so the fact that small areas of Class A are not mapped on the CAA chart and that therefore we [me included!] occasionally infringe these small corners of Class A does not pose any danger to aircraft in CAS.

Anyone else with ideas?

[IO540]

I don't think that UK has "airways" as such.

What the UK has is certain areas of controlled airspace, a lot of which happens to be Class A, and it is called "airways" in the pilot forums :)

Some of this Class A does happen to contain defined routes, some is just to protect approaches, missed approaches, sids, stars, etc.

The USA has more obvious "airways", usually VOR-VOR-VOR, but below 18000ft they are in Class E so not really relevant to a VFR pilot. France has a similar Class E route system between FL065 and FL120 (approx).

Flight planning software developers have historically had a hard time getting their heads around this stuff, and Jepp GPS databases still show what they think are 10nm wide routes in Class A but they show just the centreline (which is incredibly stupid).

What one needs to do it forget the whole concept of "airways" and just work on the actual CAS shapes. It is the shapes which you need to keep out of when flying OCAS, and if you are in CAS then ATC disregards any published routes anyway and tactically manages the traffic while keeping it within CAS.

I would be very suprised if the CAA maps were wrong. Much more likely, if indeed there is a discrepancy, somebody had incorrectly parsed some coordinate pairs.

[roweda]

This is not the first time that the UK charts have been incorrect. Late last year it was identified that part of Y53 with a base altitude of 3500AMSL was below the CTA with a lower limit iof 4500AMSL.

This was referred to NATS:


Please refer to this topic on the Flyer forum which also has a screenshot of a section of the airway below the Daventry CTA.

FLYER Forums • View topic - Where did Y53 go? (http://forums.flyer.co.uk/viewtopic.php?f=1&t=66415)

The section of Y53 has a lower limit of 3500ft AMSL but the CTA has a lower limit of 4500AMSL.

The concern is that it would appear from the chart that Class G extends up to 4500AMSL but in fact Y53 is starting at 3500AMSL.

and their response:


Thank you for your email that has been forwarded to me.

Following investigations with the Controlled Airspace Section of the Directorate of Airspace Policy at the CAA I have to conclude that you are quite correct; that section of Y53 should be portrayed on the VFR 1:500,000 charts. The appropriate paperwork has been generated to add the fillet to the next editions of the charts that are scheduled for publication early next year; in the meantime an amendment will be listed shortly on the update service at www.caa.co.uk/charts (http://www.caa.co.uk/charts).

Thank you, once again, for your invaluable feedback.


I will refer this section of M605 to them as well and will post their response in due course. I will also check the other airways which have been referenced in this topic and raise those with NATs as appropriate.

[tdbristol]

I was using the term "airways" as this is the term in the ANO.

The fact is if you plot EGWC DCT EGCJ using SkyDemonLight at 5,000', SkyDemonLight shows infringement of the south eastern corner of Class A M605 [which is 4,500' at the infringing location]. I believe that the location of 'airway' M605 by SkyDemonLight does correctly correspond with that in the ANO of 7-Apr-2011, which says (as far as I can tell) that M605 Class A is 10nm wide. I am happy to be corrected, but I suggest you try plotting it yourself. And M605 is only one of several examples.

However, if you plot exactly the same route on the current edition 37 CAA chart there is no infringement of M605 (and the infringing part of M605 is not shown on the CAA chart). Hence my confusion.

On a practical level I agree with you - I intend to take the CAA charts as the definitive guide of CAS.

Which is disappointing for SkyDemonLight - in my opinion it needs amending to match the CAA chart (+amendments) to get rid of these anomalies.

[IO540]

Interesting...

Plotting the route on 2010 charts (the only ones I have in electronic version, as a one piece UK map) there is no bust at 5000ft. I don't have the 2011 printed one to hand, and I don't have the northern part as a printed map anyway.

Plotting the route in Flitestar, using current navdata, there is also no bust at 5000ft.

The CAA map should be totally correct below FL195, regardless of any desire to de-confuse.

[roweda]

The reason that the charts are not displaying some of these errors are because they are wrong.

L10 just south of the route near Cosford from 4,500' [v. small part]
- L8 north of the route, ~10nm north of Cosford
- M605 from 4,500', starting ~10nm on ~hdg 340 from TNT: the route infringes this
- L603 just to the west of the route partly coinciding with L975

The chart showing the NE corner of L10 near the village of Little Haywood-Colwich is incorrect. It is a very small "fillet" but never the less is wrong.

I can't find any problem with L8 as there is other airspace at a lower level than the airway.

M605 is wrong on the charts. The triangle of M605 with a lower level of 4500AMSL sits inside Daventry CTA2 with a lower level of 5500AMSL.

L603 appears to be correct.

The UK charts will only show the lowest sections of airspace, whereas Skydemon Lite has got every airspace listed in its entirety and layers it onto the map so it doesn't compare to the chart.

I will refer L10 & M605 to NATs and will post their response when received.

Regards

Dave

[stevelup]

I believe that the location of 'airway' M605 by SkyDemonLight does correctly correspond with that in the ANO of 7-Apr-2011, which says (as far as I can tell) that M605 Class A is 10nm wide. I am happy to be corrected, but I suggest you try plotting it yourself. And M605 is only one of several examples.

...

Which is disappointing for SkyDemonLight - in my opinion it needs amending to match the CAA chart (+amendments) to get rid of these anomalies

I'm not sure I understand your logic here. SkyDemon is correctly displaying the airspace according to the latest data in the AIP yet this is disappointing?

[chrisN]

Years ago, when a CAA ½ mil chart was wrong (failed to show some CAS), I was told by a man from the CAA that that the UK AIP is the only definitive source; and failure to depict, or ambiguous depiction, on a chart is no excuse. He implied (in pre GPS/digital/moving map days) that my gliding club should have a paper copy (all 5 thick volumes) of the UKAIP, use only that to verify where we could fly, and not rely upon charts.

By the way, there have been several instances of known errors in the past on CAA charts. The one I mention above was in the 70’s. Missing off the Stokenchurch mast, printing some coloured CAS lines offset from the others (caused a total reprint) and that mentioned by somebody that emerged last year, are other examples. Wherever humans enter a system, errors can happen, even in the CAA.

My understanding is that when Skydemon was being set up, there was no definitive and fully accurate CAA or NATS database in digital form so they did their own.

It appears that they did not do their own topographical database (which shows coastal boundaries etc.), and it is in effect a photocopy (“raster”) of a map that is only superficially coincident with the digital (“vector”) portrayal of CAS.. The latter is accurate. The topo stuff is only as good as its source (I don’t know whose they used or how authoritative).

So as some above have said, until proved otherwise, SD can be taken as being right on airspace but may be inconsistent between where airspace and ground features are.

AIUI.

Chris N.

[IO540]

I was told by a man from the CAA that that the UK AIP is the only definitive source; and failure to depict, or ambiguous depiction, on a chart is no excuse. He implied (in pre GPS/digital/moving map days) that my gliding club should have a paper copy (all 5 thick volumes) of the UKAIP, use only that to verify where we could fly, and not rely upon charts.

That sounds like the CAA and they haven't changed much...

However I must admit I didn't know that the CAA charts contain systematic long term errors like this.

[Tim Dawson]

The SkyDemon chart will usually be more accurate than the printed CAA chart. The main reason behind this is that it's updated every 28 days, at which points airspace DOES change in the UK, though usually not significantly.

Another reason, the one apparent in this thread, is that the UK is full of such a needlessly complex system of class A airways and other miscellaneous "fillets" designed to complete the airway jigsaw puzzle. Last year it was pointed out that Y53 extended much further than the CAA chart showed, and the SkyDemon chart correctly depicted it. Anyone depending on a CAA chart (whether printed or used digitally in another product) wouldn't have seen that bit of class A. SkyDemon works by taking the raw route structure (as specified in the AIP) and constructing the airspace chunks out of it, whereas the printed chart is produced (presumably) by a person drawing lines and trying to fit them together in a way that is aesthetically pleasing.

I hope this explains what you're seeing and the discrepancy. I guess someone from NATS or the CAA will confirm where the discrepancy lies and what people should do about it. The printed 1/2mil chart is so ubiquitous that I can't believe people would be prosecuted for infringing a corner of class A that it failed to depict, but you never know.

[rn750]

Hi, Has anyone else noticed that the HDG and GS produced on the Skydemon light PLOG is inaccurate

I just plotted a route from EGBO to Fairford
track 161. If you add in a wind of 160 at 15 and an IAS of 100. The Track is correct but the GS is 89. Shouldn't it be 85??

Or am I going mad..

Confused!!

[moreflaps]

Don't have the software but could it be due to altitude?

Cheers

[stevelup]

The GS / leg time varies based on altitude and also on the length of the leg because a preset climb and descent profile is also included. It also takes into account the difference between TAS and IAS.

If you plot a triangular route and mess around withe the altitude of the whole route, you'll see even on the 'middle' leg, where there is no climb or descent, that the speed will change.

[Anonystude]

The software converts IAS to TAS using leg altitude. 100KIAS at 2,000' is about 104KTAS; with a 15kt headwind that reduces to 89kt GS...

[rn750]

Yes that all seems to tally.
I thought it might be the IAS to TAS conversion but was expecting to see OAT in there somewhere.
Thanks to all

Adie

[roweda]

NATS have replied to me today advising:


Apologies for the delay in responding but I can now confirm that we have looked at the VFR charts are the areas are indeed missing; the master data has been amended to reflect the correct airspace.


I would therefore expect there to be some chart amendments in due course.

My post of 25th April 2011 at 10:49 contains the details.

Hope this answers everybody's queries.

Dave