Quick and easy way of measuring distance on a chart
Thread Starter
Join Date: Aug 2003
Location: England
Posts: 64
Likes: 0
Received 0 Likes
on
0 Posts
Quick and easy way of measuring distance on a chart
Hi All,
Literally just started my nav exercises for my PPL. Can anyone give me a quick and easy way of estimating distance on a 1:500000 chart when its all folded up so no scale etc is viewable and without resorting to digging out the ruler?! For example if I have worked out that I am off track, how can I quickly work out by how much? Any advice much appreciated!
Thanks
Ben
Literally just started my nav exercises for my PPL. Can anyone give me a quick and easy way of estimating distance on a 1:500000 chart when its all folded up so no scale etc is viewable and without resorting to digging out the ruler?! For example if I have worked out that I am off track, how can I quickly work out by how much? Any advice much appreciated!
Thanks
Ben
Our PA28 laminated checklists all have a 1:500 000 scale on the back, plus plenty of blank space to write on!
Otherwise, 10 mile thumb.
Otherwise, 10 mile thumb.
Join Date: Sep 2002
Location: Savannah GA & Portsmouth UK
Posts: 1,784
Likes: 0
Received 0 Likes
on
0 Posts
If you have one of the vertical lines of longitude visible then measure along it. 1 minute of latitude = 1nm (don't have a half mil to hand to see what the graduations are.
Don't try measuring along the horizontal lines 'cos it don't work (unless you happen to be at the equator).
What I do though is carry a plotter with a half mil scale on it tucked into my kneeboard.
Isn't there a scale on the Frequency chart that comes with the half mil or am I imagining it?
Mike
Don't try measuring along the horizontal lines 'cos it don't work (unless you happen to be at the equator).
What I do though is carry a plotter with a half mil scale on it tucked into my kneeboard.
Isn't there a scale on the Frequency chart that comes with the half mil or am I imagining it?
Mike
Join Date: Nov 2000
Location: Kent
Posts: 603
Likes: 0
Received 0 Likes
on
0 Posts
As others have said, bend your thumb through 90 degrees, and from the knuckle to the tip of the thumb is approx 10 miles!
(now have a mental picture of FingersR measuring his thumb length ....still, could be worse!)
tKF
(now have a mental picture of FingersR measuring his thumb length ....still, could be worse!)
tKF
Last edited by TheKentishFledgling; 27th Sep 2005 at 17:04.
Join Date: Jul 2001
Location: South Yorkshire
Posts: 504
Likes: 0
Received 0 Likes
on
0 Posts
I've learned to estimate such distances reasonably accurately, e.g. to the nearest mile, just by eyeballing them.
So, FingersR get you map and with your ruler look for things (small lakes, villages, VRPs etc.) that are 2nm from something else, and try to get your eye to see that distance as 2nm. Then do the same with 4nm and then with 3 nm and 1 nm. Repeat every once in a while to re-calibrate!
To add to Gertrude's suggestion, measure the distance covered by the width of your little finger (or a biro), so you can use your finger or the biro to judge small distances. (I have a 3nm little finger and biros are basically 2nm!)
Best wishes
tp
So, FingersR get you map and with your ruler look for things (small lakes, villages, VRPs etc.) that are 2nm from something else, and try to get your eye to see that distance as 2nm. Then do the same with 4nm and then with 3 nm and 1 nm. Repeat every once in a while to re-calibrate!
To add to Gertrude's suggestion, measure the distance covered by the width of your little finger (or a biro), so you can use your finger or the biro to judge small distances. (I have a 3nm little finger and biros are basically 2nm!)
Best wishes
tp
Join Date: Apr 2002
Location: Here to Eternity
Age: 39
Posts: 96
Likes: 0
Received 0 Likes
on
0 Posts
Another nifty trick is comparing the distance to something you know on the chart -- your average ATZ is 4nm across (5nm for a large one), a MATZ 10nm across, MATZ stubs 5nm long (in the middle!), that sort of thing.
--D
--D
Also handy to think of digits (appropriate with your Prune user name!) in flying time rather than having to do a further mental calculation, eg:
Thumb width = 2 minutes
1st two finger width = 3 minutes
1st 3 finger widths = 5 minutes
4 finger widths = 6 minutes
You'll have to calibrate your own hand though!
Thumb width = 2 minutes
1st two finger width = 3 minutes
1st 3 finger widths = 5 minutes
4 finger widths = 6 minutes
You'll have to calibrate your own hand though!
Join Date: Sep 2002
Location: Savannah GA & Portsmouth UK
Posts: 1,784
Likes: 0
Received 0 Likes
on
0 Posts
Glad to see my memory is not succumbing to old age.
There are indeed distance scales on the edges of the frequency card you get with your chart, both half mil and quarter mil.
Mike
There are indeed distance scales on the edges of the frequency card you get with your chart, both half mil and quarter mil.
Mike