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Latitude and Longitude - Sectional Charts

when we're outside standing in a wide

open space the ground seems pretty flat

we even use flat charts but as you know

the earth is actually a sphere we're

close to it as pilots we need to be able

to reference precise positions on a

round surface to identify specific

points on sectional charts as well as

out in the field we use a grid system

made up of lines of latitude and

longitude on sectional charts this issue

of latitude and longitude can be a bit

confusing at first but there's some very

good reasons why you need to understand

the concept maybe you need to define a

location and a flight plan but there are

no good visual landmarks or predefined

waypoints available perhaps you need to

enter a waypoint into your GPS using

latitude and longitude you can define

any specific point on earth with a

simple set of two numbers but there is

another reason why you need to know this

stuff

it appears on your FAA written test and

that alone is a compelling reason for

you to dig in lines of latitude and

circle the globe parallel to the equator

on charts there the horizontal lines

think of the word lateral to describe

their ladder or sideways orientation

lines of longitude connect the north and

south poles they're shown on charts as

vertical lines lines of latitude and

longitude are perpendicular to each

other we can specify any point on earth

by the intersection of a line of

longitude and a line of latitude and

here's how that's done we all know what

the Equator is it's the horizontal line

around the earth that splits the globe

into the northern and southern

hemispheres here in the US we're in the

northern hemisphere the equator is the

starting point for the latitude

numbering system the units for this

system are called degrees so the equator

has a latitude of 0 degrees it's a

starting point remember other lines of

latitude march toward the poles parallel

to the equator at the North Pole the

latitude is 90 degrees and because it's

in the northern hemisphere we call it

ninety degrees north halfway between the

equator and the North Pole we had the

latitude of 45 degrees north this line

runs from main door agon going right

across downtown Minneapolis running

pretty much to the center of the

continental US is the latitude of 37

degrees north it's the line of latitude

that separates Oklahoma from southern

Kansas so in between the equator and the

North Pole

we have lines of latitude numbered

between 0 and 90 this number tells us

where the lines exist along the Earth's

north-south axis now on to longitude as

we said lines of longitude connect the

polls like latitude longitude is

specified in degrees and just as the

equator is the origin for the latitude

numbering system we have an origin for

the lines of longitude this is the zero

Degree longitude and it runs north-south

through Greenwich England this is called

the Prime Meridian and splits the earth

into the eastern and western hemispheres

that puts the continental United States

and the northern hemisphere as well as

in the Western Hemisphere

here it is on a sectional chart for the

entire country it's roughly bounded on

the east and west by the 69 degree west

and 124 degree West lines of longitude

north and south it's bounded

approximately by the 47 degree north and

25 degree North lines of latitude if we

zero in on this spot roughly in the

center of the country we zoom into the

border between Kansas and Missouri where

the 95 degrees west longitude intersects

the 39 degree north latitude the chart

pinpoints a spot on the Earth's surface

just west of Kansas City degrees are

subdivided into smaller increments

called minutes now don't get confused

these minutes measure distance not time

there are 60 minutes in each degree

minutes are shown on the lines of

latitude and longitude as small tick

marks every fifth tick mark is slightly

larger and every tenth mark is larger

still this makes it a little easier to

count them on the chart

counting the tick marks this shows the

latitude of 39 degrees

one minute north here's the latitude of

39 degrees five minutes north and here's

the latitude at 39 degrees 10 minutes

north the same thing works for longitude

here's the longitude for 95 degrees one

minute west here's the longitude for 95

degrees five minutes west and here's the

longitude for 95 degrees 10 minutes west

now if we go over three more minutes or

tick marks we find the line of longitude

that crosses the Lawrence Municipal

Airport all we have to do is to

determine its latitude and we've got it

pinpointed on the surface count up one

minute of latitude from a 39 minute line

and we see it's at 39 degrees one minute

north and there we have it the

coordinates for the airport and 39

degrees one

north and 95 degrees 13 minutes west we

can confirm this by looking at the AFD

info in the charts supplement

publication they have further divided

the minutes into tenths of minutes but

you can see that it's basically the same

thing quick review lines of longitude

connect the poles lines of latitude

encircle the globe parallel to the

equator and we can define any specific

point on earth where these lines cross

let's take a look at the Houston

sectional and apply what we just learned

we've zoomed into this area between the

latitudes of 30 and 31 degrees in the US

again because we're in the northern

hemisphere

these are degrees north we're focused on

the area between the longitude of 94

degrees and 96 degrees west because all

of the u.s. is in the Western Hemisphere

the chart has labeled these four lines

down the middle we see the 95 degree

line of longitude now recall that each

degree of latitude or longitude is

divided into 60 minutes so a line of

latitude is shown halfway between 30 and

31 degree lines this represents the

latitude of 30 degrees in 30 minutes now

this is going to help you out lines of

latitude and longitude are drawn on the

sectional chart every 30 minutes now

there's nothing magical about 30 minutes

that's just the way they're shown on the

chart to make them easier to count here

we see two additional lines of longitude

one at 94 degrees 30 minutes and the

other at 95 degrees 30 minutes note that

the lines of longitude increase in value

as you move to the west and that lines

of latitude increase in value as you

move to the north because of the way

they have the quadrants laid out every

single quadrant will have the lat and

long labels on one of its corners if you

could find that you can count out the

coordinates for any point within the

quadrant this making sense to you if not

I suggest that you pause the video and

spend a couple of minutes thinking about

this layout it's really not that

difficult

remember that lines appear every 30

minutes there are 60 minutes in each

degree and everywhere the line is

labeled time to zoom in again here's a

close-up where we can work through an

example here is the 95 degree line of

longitude and here's the 96 degree line

of logic

halfway between them is the line

representing 95 degrees in 30 minutes

the line of latitude at the top is

labeled it's 31 degrees the line of

latitude below it is unlabeled but we

already know that it's offset by 30

minutes and that latitudinal numbers get

smaller going down and larger going up

so this line of latitude must be 30

degrees in 30 minutes it's half a degree

or 30 minutes less than the 31 degree

line above it

knowing this let's find the coordinates

for the Huntsville Airport here's the

latitude line that crosses it we can

either count the tick marks down from

the 31 degree line or count them up from

the 30 degree 30-minute line there's a

little less clutter on the chart if we

count down so let's do that we can see

the large crossing line that measures 10

minutes right here five more down from

that and we get the line that crosses

the airport so it's 15 minutes less than

31 degrees and 15 minutes more than 31

degrees 30 minutes

either way this identifies the line of

latitude to be 30 degrees in 45 minutes

you have that if not pause the video and

let it sink in the closest line of

longitude is 95 degrees 30 minutes

longitudinal lines increase in values

they move to the left or west so we can

count out five tick marks to the line of

longitude that crosses the airport and

there it is the coordinates for the

Huntsville Airport are 30 degrees 45

minutes north and 95 degrees 35 minutes

west hit the pause button and take a

moment to think this through so far

we've been thinking of coordinates in

terms of degrees in minutes but

sometimes instead of minutes they are

identified as degrees and tenths or

hundreds of degrees for example 47

degrees in 30 minutes is the same as

forty-seven point five degrees think

about it point five degrees is half a

degree since there are 60 minutes and a

whole degree 1/2 degree is 30 minutes

here's another one 38 degrees in 48

minutes is the same as 38 point eight

degrees same deal as before 48 minutes

is the same as point eight degrees

multiply point

eight times sixty and you get 48 the

Huntsville Airport is at 30 degrees 45

minutes north and 95 degrees 35 minutes

west here's how we convert the minutes

to hundreds of degrees for the latitude

divided 45 by 60 that shows that 45

minutes is the same as 0.75 degrees so

the latitude is thirty point seven five

degrees north

likewise for longitude divide 35 by

sixty to yield point five eight the

latitude is ninety five point five eight

degrees west again pause the video and

run through this simple math you will

see problems on your FAA exam that

indicate the lats and lungs in both ways

so there's our view of the spherical

world describe using the latitude and

longitude coordinate system remember

that in the United States we're in the

northern hemisphere so all latitudes are

in degrees north we're also in the

Western Hemisphere

so all longitudes are measured in

degrees west east degree of latitude or

longitude is divided into 60 minutes on

sectional charts lines appear every 30

minutes and each tick mark shown on

those lines represents one minute do

some practice with your own sectional

chart and this will quickly become easy

work there are a number of test

questions about this on your FAA written

exam and there will be times in the real

world when you'll need to put this to

use and you may not have your smartphone

handy to bail you out learn it now and

you'll never be confused by it again if

you've enjoyed how we describe let's and

long from this video I can promise you

that you'll like the Gold Seal online

ground school using the same type of

knowledge transfer you will not only

learn everything you need to pass the F

a written exam you'll have a great time

doing it

Gold Seal has been delivering online

aviation training programs since 2006

longer than anyone else we're looking

forward to having you join us at ground

school comm for gold seal I'm Russ still

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