General Navigation - Departure

[ResidentInsomniac]

Hi. I am having a problem working out this, please tell me where I'm wrong.

Q: What is the distance between 00500W and 01000E at a latitude of 35°S?

So I have to find the East-West distance between 500' W of Prime Meridian and 1000'E of PM.

That adds up to 1500' difference between the two meridians.

Departure = D Long cos Lat

1500 cos 35 = 1228.72 nm


Ok that was my working, here's the brief explanation in the book:

D Long = 15 x 60 = 900’
900 cos 35 = 900 x .819
737 nm



Where did that 15degrees come from? Isn't that supposed to be 25 (1500' / 60 = 25 )


Please enlighten me.


Thanks.

[Clandestino]

One degree is 60 minutes, not 100.

[ResidentInsomniac]

I am aware of that, as you can see in my previous post (1500 (minutes) / 60 = 25nm) Anyone get my question?

[towser]

It's 5degrees west to 10 degrees east which in my book is 15degrees. It's not 1500' it's 900' (15*60).
In the question it should be written as 05,00W and 10,00E i.e. 5degrees 0minutes west and 10degrees 0minutes east

[Clandestino]

Originally Posted by Resident Insomniac

Anyone get my question?

Me.

Originally Posted by Resident Insomniac

I am aware of that

Indeed, just not aware what is the meaning of "00500W" and "01000"E.

Originally Posted by towser

In the question it should be written as 05,00W and 10,00E i.e. 5degrees 0minutes west and 10degrees 0minutes east

If we want to be completely pedantic, minute marks (') should be used also. Depending on avionics supplier E01050 might either mean 10° 30' or 10° 50' but with zeros in last two places it is pretty clear what the question was.

[ResidentInsomniac]

Thank you guys. I thought 00500W and 01000E were given in minutes, but nevertheless they are ambiguous, or is that another way of writing coordinates?

[Mark 1]

There are several conventions for writing latitude and longitude but usually a five digit group will be DDDMM followed by E or W for longitude; latitude only needs four digits (DDMM) as it will not exceed 9000.

Incidentally, the answer you give is a rhumb-line distance along the same latitude. The GC distance between those points will be less.

[ResidentInsomniac]

Thank you!