Good day learners. Welcome to our fourth lesson. I am Mr. Evuem Tubu. In this lesson we'll be continuing calculations namely bearing and coordinates. In our third lesson we ended off with direction right so now we'll be moving to bearing which is directly fed by direction.
Bearing is a more accurate way of measuring the direction between two places. True bearing is the measurement of the angle between the true north line and the line joining two places. So for example A and B from A to B. Now that means that A is our starting point and B is our end point.
What we need to do is to draw a straight line through our from place which would be A in this instance. This would be called your true north line. Then you join the two places. A and B with a pencil line.
Then after that you measure with a protractor the angle between true north which would be at zero degrees and the line joining the two places. Remember that your angle always starts at zero degrees at your true north line and red in a clockwise direction to the line that joins your two places. In this instance it would be A and B. So from your true north line right above A straight to the line joining A and B. And now we're moving over to coordinates, right?
Something that tells us our absolute location. Now I understand for this most of the time people do feel a bit overwhelmed when they start with this. But once you get the hang of it you realize how enjoyable and amazing it can be. As I said earlier on, coordinates give us absolute location and this starts with latitude and longitude.
Do you remember we spoke about latitude and longitude in lesson one? That's exactly what we need to understand coordinates. We start with latitude. Latitude tells you how far north or south the place is from 0 degrees at the equator to 90 degrees north at the North Pole.
and 90 degrees south at the south pole. Lines of latitude run across the map so these lines are horizontal lines. Longitude tells you how far east or west a place is from zero degrees at the Greenwich Meridian or prime meridian near London to 180 degrees west and 180 degrees east. Lines of longitude run lengthwise joining the North Pole and the South Pole.
So these lines are vertical lines. Now we're going to touch on a bit of a complex concept. Now each line of latitude attached to it has a degree, a minute and a second, right? And tied to that would be the position of that latitude relative to the equator. So North.
or south. Each degree is divided into smaller units called minutes and indicated by the sign of an apostrophe. There are 60 minutes in each degree.
Each minute is divided into smaller units called seconds indicated by the sign of a quotation mark. There are 60 seconds in each minute. So the same concept applies with latitude. Latitude is tied to a degree.
The degree is further divided into minutes, 60 minutes. In each minute there are 60 seconds. It is also tied to a direction, right?
How far east or west the place is relative to the Greenwich Meridian. So essentially by finding the absolute location You're looking at the position or the place at which the latitude line intersects with your longitude line. That's your absolute location. On South African maths the latitude always indicates degrees south and the longitude always indicates degrees east and why might this be because South Africa is in the southern hemisphere right we are below the equator so that is why our latitude is always south our longitude. We are located east of the Greenwich Meridian and that is why our longitude is always east.
As I highlighted earlier, coordinates describe exact location on the earth. Latitude is given first, again by stating how many degrees, minutes and seconds north or south the place is. Then longitude is given by stating how many degrees, minutes and seconds east or west the place is. So for example Cape Town International Airport would be found at 33 degrees, 58 minutes 10 seconds south and 18 degrees, that is 5 minutes 50 seconds east. Now how would we calculate this?
The first thing we need to do for our latitude, we need to state the degrees. So on our map, our map will always tell us the degrees. Remember when I spoke about map code, I told you that the first two numbers of your map index are your latitude degrees. Another way to see this, if you go on the side of your map, those degrees will also be located on the left hand side and right hand side of your map.
they will have corresponding degrees then you state your minutes now you have a minute block your minute block will start on specific minutes okay let's do a little example if i want to go to a school near bonella in block b1 and i want to know the absolute location of that school i need to determine the coordinates here is how you will determine the coordinates of the school the first thing you do you need to locate the school in the block so there's the school in block b1 now when you write your coordinates you always start with latitude the the dot where the school starts to your minute bar right that line represent your latitude then you draw A vertical line again from the point to your longitude minute bar. Now you can see you have absolute location where your latitude meets longitude. Now we are able to read our minutes.
We start with south. On the Durban map we are fortunate to have the degrees. but other maps don't have the degree so you can look at your map index right here remember in lesson one we told you that the first two numbers will give you latitude the second two numbers will give you longitude so here our latitude is 29 degrees the feature is located between the 51st minute and the 50th minute a feature always takes the smaller number. So this one is between 50 and 51. So it takes 50 minutes.
If it was between 1 and 2, it would take 1. And for our seconds, this whole bar represents 1 minute, right, from 50 to 51. So the seconds in here are 60 seconds. Now we have different methods of calculating this. You could use estimation or the time 60 rule. and in this video we will be using estimation now if you look at this bar the line we've made looks like it's halfway between the bar the bar is about 4.1 centimeters and our feature is at about 1.9 centimeters now if that's just less than half it's just less than 30 seconds half the bar so you can as long as it's more than 25 and less than 30 it should be acceptable so we can say it is 20 8 seconds. Now your teacher will have a margin of error here.
Do not be too worried. Don't go too low. Don't go too high.
As long as you're in the correct range. We have the same approach for our longitude. We start with our degree.
We can look at our map index again. Our degree is 30 degrees on our map index. So we know we can write 30 degrees for longitude. Our minutes.
Now this is between 57 minutes and 58 minutes. Right? And the rule is it gets the smaller minutes.
So it is 57 minutes. And on this bar, our line is exactly at halfway, at the halfway mark. Now how many seconds would be half a minute? 30 seconds. So then we have...
30 seconds east. Now how would we read our coordinates for the school near Bonella in B1? The school is located at 29 degrees, 15 minutes, 28 seconds south and 13 degrees, 57 minutes, 30 seconds east. Please make sure that you always do it in the order in which it is shown. It is always first latitude, then longitude.
And when you present your minutes, you present from degree to second. So in the order of degree, minute, second and direction. And then for your longitude again, degree, minute, second and direction. Now learners.
In the past series of lessons, we've looked at basic methods, specifically calculations and interpretation. In our next lesson, we will be specifically focusing on activities. So what we'll be doing... is practice of all of the things that we would have learned so far.
But then once again, thank you so much for joining us. And remember, it's always important to practice. So do check our self-marking assessment right below. And remember to subscribe.