VFR navigation question
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One thing Mad Bear does not give us is his experience level. Reading between the lines he is not yet at the Nav stage of a PPL and just trying to find his way round the local area, if so a lot of what has been talked about is not particularly relevant. If this is the case he needs to do similar to Pistongones technique, learn obvious features near enough to the field to know that you can get back from there, if needed using a set heading and time (less than 5 mins), do this in as many directions as you can, then expand the range at which you find known features, you will soon get familiar enough with your local area to find your way without a map (though of course you should still carry one!).
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Pistongone...
The point you're missing is the sums I'm using to get myself accross the channel are based on my inflight experience NOT what I do on the ground. Also do you arrange your flight so that your groundspeed is a convenient factor of 60? Or do you fly at 2350rpm etc etc however your POH tells you to fly an aeroplane?
The point I was making was I think in my opinion that people spend to much time working out the numbers and basic their assumptions on other peoples' guessing (ie forecast winds aloft). Becasue of that I prefer to have a route on a chart and estimate my headings and timings dependant on what I think is right at the time. And THAT gets me accross the channel not working out the numbers beforehand.
As I say if your method works for you then that's grand.. mine works for me!
Bottom line is.. GPS rocks!
The point you're missing is the sums I'm using to get myself accross the channel are based on my inflight experience NOT what I do on the ground. Also do you arrange your flight so that your groundspeed is a convenient factor of 60? Or do you fly at 2350rpm etc etc however your POH tells you to fly an aeroplane?
The point I was making was I think in my opinion that people spend to much time working out the numbers and basic their assumptions on other peoples' guessing (ie forecast winds aloft). Becasue of that I prefer to have a route on a chart and estimate my headings and timings dependant on what I think is right at the time. And THAT gets me accross the channel not working out the numbers beforehand.
As I say if your method works for you then that's grand.. mine works for me!
Bottom line is.. GPS rocks!
Blah Blah Blah
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As a sort of Thursday afternoon answer.
(If i was you i would get a big mug of coffee for this one)
http://users.erols.com/dlwilson/gps.html
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mad bear....
some good advice here...but then you got into GPS and NUMBERS and then some..( by the way if you were with me and i had a GPS i would turn it off )
heads up guys..he started simply saying ( since we know he's not yet reached navigation stage yet ) as i understand it..he was having trouble recognizing features to get used to in his locality and by that i assume he refes to the area in which he ( sorry..better not assume too much )/ or she trains and the airfield area...so see my original submission..
and by the way there is a way of reducing your altitude on google so you can see mountains with any sizeable height but it distorts a bit and tends to flatten buildings ( i'm still learning also )..go to the grey vertical lever near the right hand arrow button which swivels you round...hold it down and watch yourself descend so you can see the horizon..
good luck...and keep your eyes off the dashboard and outside the aircraft..
some good advice here...but then you got into GPS and NUMBERS and then some..( by the way if you were with me and i had a GPS i would turn it off )
heads up guys..he started simply saying ( since we know he's not yet reached navigation stage yet ) as i understand it..he was having trouble recognizing features to get used to in his locality and by that i assume he refes to the area in which he ( sorry..better not assume too much )/ or she trains and the airfield area...so see my original submission..
and by the way there is a way of reducing your altitude on google so you can see mountains with any sizeable height but it distorts a bit and tends to flatten buildings ( i'm still learning also )..go to the grey vertical lever near the right hand arrow button which swivels you round...hold it down and watch yourself descend so you can see the horizon..
good luck...and keep your eyes off the dashboard and outside the aircraft..
Blah Blah Blah
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I thought someone might pick out
"intentional degradation of non-military GPS accuracy "
I also thought that the above statement was fairly common knowledge. it is one reason why I do not rant on about GPS useage. Although they are good and accurate enough for GA as long as you use map, compass and timer as well.
I think we could well be off on a tangent here!!
Last edited by gcolyer; 28th Sep 2006 at 13:46. Reason: becasue i can.
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Kirsty,
Darth Bovine, the reason his gps showed bad info was user error, i n as much as he had the wrong datum for this side of the world! This would probably not have happened had he had training in the correct use of GPS, hence the need for proper training in its safe use!
Darth Bovine, the reason his gps showed bad info was user error, i n as much as he had the wrong datum for this side of the world! This would probably not have happened had he had training in the correct use of GPS, hence the need for proper training in its safe use!
Sorry for the thread hijack by the way!
Cheers,
R.
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Darth,
if you look at the setup menu, depending on what unit you have, you will probably find a list of datums. Here you can set your unit to standard Lat and Long, or Decimal System for easy entry of co-ordinates, then mine has a long list of datums, you can get it to use OS mapping grids, american, tokyo and all other strange datums. I have experimented when in the car and dont seem to get much of a difference, so i cant proffess to be an expert, you could however try reading GColyers site. You will need a VERY BIG coffee mug.
if you look at the setup menu, depending on what unit you have, you will probably find a list of datums. Here you can set your unit to standard Lat and Long, or Decimal System for easy entry of co-ordinates, then mine has a long list of datums, you can get it to use OS mapping grids, american, tokyo and all other strange datums. I have experimented when in the car and dont seem to get much of a difference, so i cant proffess to be an expert, you could however try reading GColyers site. You will need a VERY BIG coffee mug.
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I've just had a quick glance at that David Wilson's site.
Very interesting, but unless I am missing something, it tells me what I already knew which is, basically, GPS is accurate to less than the width of the average motorway.
I'd say that's adequate for navigation, most of the time
I don't think anybody can accuse me of hijacking this thread in favour of GPS though.
The error between WGS84 and some other commonly used datum should be of the order of a few hundred metres; not enough to make a difference in any practical enroute navigation application. If the unit was showing the correct lat/long coordinates but its moving map was showing the location some miles away, that's a pretty basic software problem. I saw that once, on an old version of Jeppesen FliteMap running on a tablet PC, somewhere in the Greek islands. The error was probably less than what one would have got using the nearest VOR. I reset the PC and it went away. The IFR GPS (KLN94) was fine all along.
Very interesting, but unless I am missing something, it tells me what I already knew which is, basically, GPS is accurate to less than the width of the average motorway.
I'd say that's adequate for navigation, most of the time
I don't think anybody can accuse me of hijacking this thread in favour of GPS though.
The error between WGS84 and some other commonly used datum should be of the order of a few hundred metres; not enough to make a difference in any practical enroute navigation application. If the unit was showing the correct lat/long coordinates but its moving map was showing the location some miles away, that's a pretty basic software problem. I saw that once, on an old version of Jeppesen FliteMap running on a tablet PC, somewhere in the Greek islands. The error was probably less than what one would have got using the nearest VOR. I reset the PC and it went away. The IFR GPS (KLN94) was fine all along.
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Wrong datum is a very common error, especially if flying club a/c. As many people are neither trained in using a GPS unit nor take the time to self-study, they tend to fiddle - and change the datum to something useless. Happened to me once flying a club a/c, had the GPS on w/o really looking (t'was a local bimble in an area I know by heart) and, approaching a VRP, discsovered it was about 5 miles out on the GPS. Checked after landing and sure enough, the datum was set to something weird. Reset it and hey, presto! all was well again. Just shows that it's idiotic NOT to train the use of GPS during the PPL.
Anyway, back to the OP. FWIW, one thing that helped me early in my flying was to not only look at the charts but also at road maps. In fact, I always had one with me in the a/c. These maps often display roads and topographical features in a better way than aeronautical charts. Plus, you're probably used to looking at them and finding you way round using them! Obviously not for primary navigation, but helps. Another thing to remember is that you will be looking at any feature at an angle, while the map depicts lakes, towns, etc as seen from straight above. Unless you do your PPL in the Space Shuttle, an unlikely view. In general the UK's a bitch for visual nav anyway, as there are relatively few distinctive features - it all sort of looks alike (at least in the South East), even the Tescos all have the same sign
It therefore helps to try to pick isolated landmarks, like power stations, cement factories and the like. Initially, make sure you have something to refer to every 10 miles or so, as you progress you'll increase the distance between these landmarks. Venturing further afield, always try to find some long(ish) feature running perpendicular to your track, such as a highway, river, ridgeline, etc. that can act as a sort of 'catchline'. I'd be careful using lakes as landmarks, especially if they are not islolated as they can look very different at an angle than as depicted on the charts. Also bear in mind, that if said lake is a reservoir, it can change shape and size considerably.
HTH
Anyway, back to the OP. FWIW, one thing that helped me early in my flying was to not only look at the charts but also at road maps. In fact, I always had one with me in the a/c. These maps often display roads and topographical features in a better way than aeronautical charts. Plus, you're probably used to looking at them and finding you way round using them! Obviously not for primary navigation, but helps. Another thing to remember is that you will be looking at any feature at an angle, while the map depicts lakes, towns, etc as seen from straight above. Unless you do your PPL in the Space Shuttle, an unlikely view. In general the UK's a bitch for visual nav anyway, as there are relatively few distinctive features - it all sort of looks alike (at least in the South East), even the Tescos all have the same sign
It therefore helps to try to pick isolated landmarks, like power stations, cement factories and the like. Initially, make sure you have something to refer to every 10 miles or so, as you progress you'll increase the distance between these landmarks. Venturing further afield, always try to find some long(ish) feature running perpendicular to your track, such as a highway, river, ridgeline, etc. that can act as a sort of 'catchline'. I'd be careful using lakes as landmarks, especially if they are not islolated as they can look very different at an angle than as depicted on the charts. Also bear in mind, that if said lake is a reservoir, it can change shape and size considerably.
HTH
mad_bear,
I can understand how you feel as it took me a long time to get confident about flying around my local area even after I got my PPL. I found it helpful to choose a few landmarks around the area and to work out the approximate compass bearing relationship between them and to my home base. Get to know those landmarks well and, as long as you know roughly where one of them is, you can quickly fly a heading which will bring the certainty of seeing it, even in reduced visibility. You will then, with practice, develop a sense of spatial awareness based on compass bearings. In my opinion it is important to develop this skill before getting used to having a GPS.
If you are into FS2004 with VFR scenery, you can practice this in your local area at no extra cost.
I can understand how you feel as it took me a long time to get confident about flying around my local area even after I got my PPL. I found it helpful to choose a few landmarks around the area and to work out the approximate compass bearing relationship between them and to my home base. Get to know those landmarks well and, as long as you know roughly where one of them is, you can quickly fly a heading which will bring the certainty of seeing it, even in reduced visibility. You will then, with practice, develop a sense of spatial awareness based on compass bearings. In my opinion it is important to develop this skill before getting used to having a GPS.
If you are into FS2004 with VFR scenery, you can practice this in your local area at no extra cost.
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172, what datum was selected to cause an error that big?
Going back to the ground feature recognition business: I don't think the pilot is free to pick landmarks. He has to use whatever is on the CAA chart, and that doesn't show that much detail. Not even the 1:250k chart, which is better for dead reckoning than the 1:500k one.
I gather that specialised flyers, e.g. pipeline and power line inspection people, use the 1:50k Ordnance Survey charts. I don't know how they manage something like that in the cockpit, but one can run them on a GPS running Memory Map. However, such a chart is going to be very hard to use for normal flying.
So it's back to the CAA chart, or whatever chart you can get for some other country you are flying in, and what appears on that. One can't make use of a ground feature that doesn't appear on the chart. I don't think learning the local area is of much help; that's what instructors do by rarely venturing past the nearest crease in the chart but it won't work further afield.
Going back to the ground feature recognition business: I don't think the pilot is free to pick landmarks. He has to use whatever is on the CAA chart, and that doesn't show that much detail. Not even the 1:250k chart, which is better for dead reckoning than the 1:500k one.
I gather that specialised flyers, e.g. pipeline and power line inspection people, use the 1:50k Ordnance Survey charts. I don't know how they manage something like that in the cockpit, but one can run them on a GPS running Memory Map. However, such a chart is going to be very hard to use for normal flying.
So it's back to the CAA chart, or whatever chart you can get for some other country you are flying in, and what appears on that. One can't make use of a ground feature that doesn't appear on the chart. I don't think learning the local area is of much help; that's what instructors do by rarely venturing past the nearest crease in the chart but it won't work further afield.
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again..as i understand it we are only talking about getting used to features around the airfield and training area...not doing a cross country so..no maps...just local features so as to find the airfield and set himself/herself up for downwind/base and finals.... right ??!!...not into cross countries yet...
right ??!!...not into cross countries yet...
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How about looking at some nice landmarks in North London
1- Elstree Lake
2 - St Albans Cathedral / city
3 - Old Leavesden aerodrome (NW Watford)
4 - Hatfield
5 - Lea Valley resorvoirs
6 - M25 Motorway
Suggest you plan a local solo flight using these features in your plan and fly in your armchair the night before. Back it up with a bearing on LAM VOR or BPK and you should be able to extend your knowledge and confidence of the North London area without too many prob's
In that area though if "unsure of postn" for more than a couple of minutes then get straight onto 121.5 or Luton / Thames radar as appropriate and "confess"
Good Luck !
1- Elstree Lake
2 - St Albans Cathedral / city
3 - Old Leavesden aerodrome (NW Watford)
4 - Hatfield
5 - Lea Valley resorvoirs
6 - M25 Motorway
Suggest you plan a local solo flight using these features in your plan and fly in your armchair the night before. Back it up with a bearing on LAM VOR or BPK and you should be able to extend your knowledge and confidence of the North London area without too many prob's
In that area though if "unsure of postn" for more than a couple of minutes then get straight onto 121.5 or Luton / Thames radar as appropriate and "confess"
Good Luck !
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IO540 Can't remember, that was a couple of years ago. Also, it may have been less than 5 miles but it definitely was a serious error, miles, not a couple of hundred meters.
What this emphasises (as if that was needed) is the absurdity of not training people in the use of GPS.
What this emphasises (as if that was needed) is the absurdity of not training people in the use of GPS.
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Navigation, however you do it takes practice and more practice. Hopefully you will be properly taught the basics and you will make sure that you understand them (ie don't hesitate to ask if your intructor makes a complete bish of teaching it). Sadly there are many instructors who cannot navigate very well themselves. Most of us navigate using a mixture of techniques, all of which are valid providing the user understands them.
"Track crawl" ie the technique of navigating by ground features is difficult to pick up but extremely useful. Afterall it combines enjoying the view with navigation. I find the half mil charts about as good as useless except for planning long legs. The quarter mill is far better and can be used to pick out the shapes of towns, lakes and woodland (very useful). Often it is a combination of features that confirms a location (eg motorway junction with forrest on its east side). Helicopter pilots will also use 1:50,000 OS maps, but only for finding a private site or for low level poor viz nav in a specialist role.
Get your instructor to point out land marks AND their relative position to Elstree. The Buncefield depot (or what's left of it) is a good one as it is also close to the Luton zone. Also learn the shape of the local motorway junctions - there are many in that area, but by judgeing the directions each motorway goes in helps with identification. Familiarity will eventually mean that you will be able to readily recognise where you are.
By the way, I think we all as students were concerned with navigation at early stages of the ppl. You are not alone!
"Track crawl" ie the technique of navigating by ground features is difficult to pick up but extremely useful. Afterall it combines enjoying the view with navigation. I find the half mil charts about as good as useless except for planning long legs. The quarter mill is far better and can be used to pick out the shapes of towns, lakes and woodland (very useful). Often it is a combination of features that confirms a location (eg motorway junction with forrest on its east side). Helicopter pilots will also use 1:50,000 OS maps, but only for finding a private site or for low level poor viz nav in a specialist role.
Get your instructor to point out land marks AND their relative position to Elstree. The Buncefield depot (or what's left of it) is a good one as it is also close to the Luton zone. Also learn the shape of the local motorway junctions - there are many in that area, but by judgeing the directions each motorway goes in helps with identification. Familiarity will eventually mean that you will be able to readily recognise where you are.
By the way, I think we all as students were concerned with navigation at early stages of the ppl. You are not alone!
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Originally Posted by pistongone
As a sort of Thursday morning test, can any of you guess what was the problem with his GPS, as we did indeed arrive at Staplford on track and time??
Map datum wrong ?
As a sort of Thursday morning test, can any of you guess what was the problem with his GPS, as we did indeed arrive at Staplford on track and time??
Map datum wrong ?
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Hi Everyone,
I am currently building up my solo nav hours for my PPL. I find VFR navigation fairly easy around my local area as there are big landmarks and other airfields. My question is; could I take a GPS unit up with me as back up in case I ever found myself lost or just to confirm position fixes when flying routes further afield? Would it be wise therefore to take it on a first cross country solo as a safety aid?
Just out of curiosity.
Thanks.
Andrew
I am currently building up my solo nav hours for my PPL. I find VFR navigation fairly easy around my local area as there are big landmarks and other airfields. My question is; could I take a GPS unit up with me as back up in case I ever found myself lost or just to confirm position fixes when flying routes further afield? Would it be wise therefore to take it on a first cross country solo as a safety aid?
Just out of curiosity.
Thanks.
Andrew