Reading Co-ordinates on 1:500,000 Chart

[Lew747]

Hey all,


Just asking for some help as I am struggling with reading co-ordinates on the 1:500,000 UK charts.

I'm wishing to take my nav exam in a few weeks after putting it off for a long, long time. I've gone through the confuser and series 3 nav manual but neither have provided me with help on reading the chart.
E.g, in the confuser the co-ordinates, for say, Wattisham are N5207.62 E00057.47. The ONLY part I can seem to interpret is the N52* part :bored:

Anyone got some tips or some online links which can help me?

Just another point, the confuser states as saying it represents 'All current questions and answers". I know the nav exam comprises of a route and a Plog which you have to fill in. The routes in the Confuser are:

St Mary's (Scilles Isles)- Wolf Rock lighthouse- Camelford Quarry- Plymouth (Alternate- Bodmin)
Yeovil- Top of Climb- Ystradgynlais- Aberporth (Alternate- Swansea)
Shoreham- Farthing Corner- Wattisham (Alternate- Clacton)
Shipdam- Tatenhill- Bourne (Alternate- Cosford)

Would one of these routes be present in the real exam I will undertake? Does anyone recognise any of these places when they sat their nav exam?

Hope you can help, as I've found Nav to be the hardest exam to date. God only knows how hard it must be for me at ATPL Level :{:ugh:


Lewis :)

[jxc]

The ppl nav exam I did July last year was headcorn to somewhere peterbrough i think
not that either

[Crash one]

If you look at the top or bottom of the chart or sides you will see degrees marked in whole numbers. Along these lines are graduations of 1 minute, 5min & 10min divisions are longer like on a ruler. At the 1/2 degree point is a continuous line but no grads. Graduations in the North/South direction (Latitude) are 1nm same as your ruler. East/West they are not because the smaller circle = less per degree, You can walk round the planet at the north pole in 3 or 4 paces at Lat 90. At the equator it's a bit further but still 360degrees.
Any good?

[juliet india mike]

When I did my nav exam I got locked in to thinking there were 100mins per degree. The lat + long refs then made no sense until after 10 wasted minutes the penny dropped....:O

[tow1709]

Maybe this is the problem...

There are different ways in which the degrees and subdivisions of degrees can be expressed.

Google Earth, for example uses "ddº mm' ss.ss" i.e. degrees, minutes, seconds, and after the decimal point are the tenths and one hundredths of a second. This was what I was taught in geography at school.

Your Confuser example uses (d)ddmm.mm. In other words the degrees and whole numbers of minutes are given in one string without a break before the point, and after the point are the decimal fractions of a minute. So your example latitude N5207.62 E00057.47, translates to N 52º 07 min plus 0.62 of a minute which is about 37 sec.

I have put the d in brackets because longitudes are always given 3 digits since they can go up to 180º (latitudes only go up to plus or minus 90º).

So E 00057.47 translates to 0º 57' plus 0.47 of a minute or about 30 sec.

GPS receivers can be set to work in degrees plus decimals of a degree e.g. 57.7500 would be 57º plus 0.75 of 60 (minutes in a degree) or 45 minutes. Also east and west are given positive and negative values respectively as are north and south, so beware of this.

None of the Confuser examples you quoted was in my exam, it was a different route entirely.

I hope this helps.

Wishing you success in the exam.

[Lew747]

I think the penny has finally dropped! Hallejuah! :D:D:D Thanks for your help! Still gonna need a bit more practice though. The degrees and minutes im able to find ok, but the seconds I assume are too small to really be of much significance on the chart?

I think it'll be straight onto the GPS and electronic flight computers once i've qualified! :} Can you use electronic flight computers when undergoing ATPL training? Or you stuck with the CRP-5 or similar?


Lewis :ok:

[Oldpilot55]

You can ignore seconds because of the following...one minute of latitude equals one nautical mile so if you read your latitude off the chart to the nearest minute then your position (or distance between will be correct to 1 nautical mile). Minutes of longitude vary and one minute will only be (approximately) a nautical mile at the equator. If you look at a globe you will see that the lines of longitude converge to the north and south poles.

[Dicky Birded]

Hi,

There are three CAA papers apparently.

I sat the Nav exam ten days ago and it covered the South West area.

Just remember Northings degrees are two digit and Eastings/Westings three digit.
These are divided into 60 minutes which are marked in increments on the map.
You don't need to worry about seconds as they are too small.

HTH.

[Whopity]

For the purpose of Nav exams you are only likely to be required to define a position to one nautical mile i.e. 1 minute of longitude. Because we now have co-ordinates, originally designed for aligning an INS and now GPS equipment capable of giving positions to within a few yards, there will be more than 4 digits in the position. You simply don't need anything after the fourth digit, assuming its in degrees and minutes, any other format is useless for chart navigation.

[bingofuel]

Rather an obvious suggestion, but why do you not ask your Flying Instructor to explain it to you.?

[Lew747]

Had an instructor down my club explain,only to go on and say 'hang on, these coordinates in this book are incorrect!' (And he's an airline pilot).

If only they made it as easy as reading a 6 figure grid reference from an Ordnance Survey map! Thats what I was taught to read during geogprahy at school. The more I look at it though, it's just as simple! :)

[IO540]

N5207.62 E00057.47

Is there a GPS that actually uses this representation?

OK, I can see that it is obvious, because "everybody" knows that degrees latitude can only be 00 to 90 (2 digits) hence the "52" must be whole degrees, and "everybody" knows that degrees longitude can be up to 180 (3 digits) hence the "000" must be whole degrees... but this is pretty confusing.

[RTN11]

Relying on GPS is all well and good, but you should still have some idea what you're putting in.

If you put rubbish into the GPS, it'll give you rubbish back.

For the ATPL exams you will still need to use a CRP-5, no electronic flight computers or programmable calculators. I think this is so you actually have some idea what the wind drift means rather than just putting numbers into a machine.

[Hoots Mon]

I did my Nav over a year ago now. All I can suggest is to be *very* careful and plot the position as accurately as you can. My exam question was somewhere down in the SW/Wales area as far as I can remember, not sure which. You end up looking for a landmark from the description in the question, you see the same landmark thats near where the co-ordinates are, you assume its the right one. Be careful, it could be a severe red herring. If you don't pick up on it, the question will cease to make sense later on (I think you end up being told to fly in a particular direction to another point, if you've picked the wrong landmark, then you won't be flying in that dictated direction) and you waste time going through it allll again :{. When you plot them precisely, you get the correct more obscure landmark, hidden in the chart clutter and the rest of the question then makes sense. "Sneaky bar stewards" is what I thought of those exam chaps at the CAA :E

[tow1709]

IO540 asks if there are GPS that use this "N5207.62 E00057.47" representation.

My old Garmin III+ (admittedly not a specialist aviation GPS) can display any of the following

N DDº.DDDD EDDDº.DDDD - degrees plus decimals of a degree
N DDº MM.MMM E DDDº MM.MMM - degrees plus minutes and decimal fractions of a minute (default setting)
N DDº MM' SS.S" which goes down to decimal fractions of a second.

The display actually leaves a blank space after the latitude N (or S) where a redundant leading zero would be.

I only brought up the subject of GPS and Google Earth as examples to show that several different conventions exist

[IO540]

For the ATPL exams you will still need to use a CRP-5, no electronic flight computers or programmable calculators. I think this is so you actually have some idea what the wind drift means rather than just putting numbers into a machine.

Actually, this serves to separate the real men from the sheep, which is the objective of the European study process.

In particular, the use of the non-wind side of the slide rule as a multiply/divide calculator (which, BTW, I can do, having used a slide rule for real at school in the 1960s) is nothing more than a throwback to the 19th century.

The Americans dumped the circular slide rule (as a mandatory thing) years ago. An awful decision, because the whole of the USA is now covered with aircraft wreckage.

[ExSp33db1rd]

N5207.62 E00057.47

It is becoming more confusing as GPS co-ordinates usually use degrees, minutes and decimals of a minute.

In this case it can't be 52 deg, 07 min. and 62 seconds, 'cos there are only 60 secs in a min. so it must be 07.62 mins - as someone said around 37 secs if you are trying to plot on a large scale chart.

The problem is when both Lat. and Long. show values less than .60, one than has to know if one is dealing with minutes and decimals of a minute, or minutes and seconds.

Time the world kicked seconds in to touch, and just used decimals of a minute.

At the end of the day, stop trying to do a maths exam in a rattling steel cabinet, do not strive after theoretical accuracy - except in the exam of course !

[airborne_artist]

In this case it can't be 52 deg, 07 min. and 62 seconds, 'cos there are only 60 secs in a min. so it must be 07.62 mins - as someone said around 37 secs if you are trying to plot on a large scale chart.

However, as already pointed out further up, the seconds/decimals of a minute are insignificant for the task in hand. Vital if you are directing weapons onto a battlefield, but not important when flying as a PPL.