Wednesday, July 7, 2010

EARTH as a SPHERE - Form 5

Understanding of the position of Latitude and Longitude is very important.
1.  Latitude begins at the equator (0) and ends at the North Pole (90 N) and South Pole (90 S).
2.  Latitudes are all circles, the equator being the biggest and the North Pole and South Pole as a single dot.
3. Longitudes or Meridians are semi-circle lines from the North Pole to the South Pole.
4. Longitudes begin from the Greenwich Meridian (0 MG) and ends at 180 (180 International Date Line/IDL)
. This means that Longitudes from 0 MG goes East until 179 E and goes West until 179 W.

Positions of points on the surface of the earth:
1.  All points on the surface of the earth are located as  P(latitude....., longitude......)
2.  The important thing is to know the difference in degree between two points.
     e.g. 1 :  P (0,  40 E)       Q (0,  30 W)     Therefore, the difference = 70.
     e.g. 2:  M(30 N,  50 W)     N (20 S,   50 W)   Therefore, the difference = 50.

Distance between Two points/places:
There are only 2 ways of calculating the distance between two places on the surface of the earth.
1.   If the two points/places are between North and South (one in the North and the other in the South), then the   Distance = difference in degrees  X 60

eg. P(30 N, 70 W)     Q (20 S, 70 W)
      Distance = 50 x 60 = 3000 nautical miles.

2.  If the two points/places are between East and West (ie. along the common latitude), then 
the  Distance = difference in degrees  X  60  X Cosine of the common latitude

eg. P(60 N, 40 E)     Q (60 N, 30 W)
     Distance = 70 x 60 x cos 60N  = 2100 nautical miles.

Calculations involving Speed, Time and Distance:
1.  If there is a question on this matter, then use the simple law:  Speed = Distance/Time.
2.  The speed is usually given in he question.
3.  The distance is calculated using the formula above (as in this topic - distance between two points)
4.  So, Time = Distance/Speed.

That's about all...  You can now try solving questions on this topic...
Have a nice day...


Anonymous said...


Anonymous said...

really helping , thank you so much :)

Anonymous said...

Thank you so much, Sir! I've finally understand this chapter, it's very simple as ABC :)

Anonymous said...

thank you so much! i can understand well now :)

Anonymous said...

thank you sir

Anonymous said...

Can u explain how to calculate the shortest distance along the longitude n the latitude.

DESS said...

Distance between 2 points along the longitude = the difference in angle X 60.
Distance between 2 points along the latitude = the difference in angle X 60 X the cosine of the latitude.


Anonymous said...

thank you for sharing the info...

Anonymous said...

Thank you! it really helps me a lot