G Nav Questions - 2
Thread Starter
Joined: Aug 2002
Posts: 310
Likes: 0
From: U and K
G Nav Questions - 2
Hi
Need help on these questions please ...
On a Mercator chart a straight line is drawn between point A (34 23'S 007 00'W) and point B (34 23'S 009 00'E). Use this info to answer following...
The chart distance of the line is 83cm. The scale of the chart at 34 23'S is:-
a) 1:954,000
b) 1:1,772,000
c) 1:1,160,000
d) 1:2,150,000
--------------------
The scale of the chart at the equator is:-
a) 1:954,000
b) 1:1,772,000
c) 1:1,160,000
d) 1:2,150,000
-------------------
The rhumb line track from A to B is:-
a) 090 T
b) 090 M
c) 270 T
d) 270 M
-------------------
The great circle track from A to B measured at A is:-
a) 086T
b) 090T
c) 094T
d) 099T
Any help will be greatly appreciated !
Best regards,
Seabass
Need help on these questions please ...
On a Mercator chart a straight line is drawn between point A (34 23'S 007 00'W) and point B (34 23'S 009 00'E). Use this info to answer following...
The chart distance of the line is 83cm. The scale of the chart at 34 23'S is:-
a) 1:954,000
b) 1:1,772,000
c) 1:1,160,000
d) 1:2,150,000
--------------------
The scale of the chart at the equator is:-
a) 1:954,000
b) 1:1,772,000
c) 1:1,160,000
d) 1:2,150,000
-------------------
The rhumb line track from A to B is:-
a) 090 T
b) 090 M
c) 270 T
d) 270 M
-------------------
The great circle track from A to B measured at A is:-
a) 086T
b) 090T
c) 094T
d) 099T
Any help will be greatly appreciated !
Best regards,
Seabass
Jet Blast Rat
Joined: Jan 2001
Posts: 2,081
Likes: 0
From: Sarfend-on-Sea
Scale = Chart length / Earth Length
Chart length = 83 cm
Earth length is departure = ch. long (minutes) x cos lat = 16 x 60 x cos 34°23' = 792 nm
change to centmetres : 792 x 1852 x 100 = 146,728,000 cm
Scale is 83 : 146,728,000 however should be expressed as 1 : something so divide both sides by 83. Scale is then 1 : 1,768,000.
----------------------
For scale at the equator divide the denominator of the scale (the "1,768,000" bit) by cos of the latitude.
1,768,000 / cos 34°23' = 2,142,000. Scale is 1: 2,142,000
---------------------
They are at the same latitude, rhumb-line track must be 090° or 270°. B is further East so track is 090°.
--------------------
The rhumb-line track is 090°. If you draw a diagram the great-circle track at A is greater than the rhumb-line track. The difference is conversion angle.
C.A. = 0.5 x ch.long x sin mean lat = 0.5 x 16° x sin 34°23' = 4.5°
90° + 4.5° = 94.5°
Any better answer requires diagrams, so you should contact your training povider. Best of luck!
Send Clowns
Gen Nav instructor, BCFT
Chart length = 83 cm
Earth length is departure = ch. long (minutes) x cos lat = 16 x 60 x cos 34°23' = 792 nm
change to centmetres : 792 x 1852 x 100 = 146,728,000 cm
Scale is 83 : 146,728,000 however should be expressed as 1 : something so divide both sides by 83. Scale is then 1 : 1,768,000.
----------------------
For scale at the equator divide the denominator of the scale (the "1,768,000" bit) by cos of the latitude.
1,768,000 / cos 34°23' = 2,142,000. Scale is 1: 2,142,000
---------------------
They are at the same latitude, rhumb-line track must be 090° or 270°. B is further East so track is 090°.
--------------------
The rhumb-line track is 090°. If you draw a diagram the great-circle track at A is greater than the rhumb-line track. The difference is conversion angle.
C.A. = 0.5 x ch.long x sin mean lat = 0.5 x 16° x sin 34°23' = 4.5°
90° + 4.5° = 94.5°
Any better answer requires diagrams, so you should contact your training povider. Best of luck!
Send Clowns
Gen Nav instructor, BCFT
Joined: Aug 2003
Posts: 69
Likes: 0
From: EU
here my answers:
departure: 16 degrees*60miles*cos 34=794 miles
794miles*1.852=1470 km
1470000m:0.83=1772000
answer B.
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then the scale contract at the equator(biger) and expand away from equator
1772000 : cos 34=2137418
answer D
--------------------------------------------------------
rhumb line 090T
answer A
----------------------------------------
last question: we are in the south!!!
16 degree * sin34=9 degrees
9:2=4.5 degree
090+4.5=94.5 degree
departure: 16 degrees*60miles*cos 34=794 miles
794miles*1.852=1470 km
1470000m:0.83=1772000
answer B.
-------------------------------------------------------
then the scale contract at the equator(biger) and expand away from equator
1772000 : cos 34=2137418
answer D
--------------------------------------------------------
rhumb line 090T
answer A
----------------------------------------
last question: we are in the south!!!
16 degree * sin34=9 degrees
9:2=4.5 degree
090+4.5=94.5 degree
