Scale diagram Watch
To bisect BAD:
- Place the compass needle on point A.
- Draw the pencil around at a random distance (say, 2 cm - but it doesn’t matter) so you have an arc crossing both lines AB and AD.
- Put the compass needle on the point where the arc intersects a line (it doesn’t matter which you start with).
- Draw another arc around that point so part of the arc is between AB and AD.
- Repeat the step but from the other line. The two arcs should meet between AB and AD.
- Draw a line through point A and the intersection point of both arcs. Continue the line till it’s out of the shape.
Then the runway must be on the side of that line (the “angle bisector”) which is closer to AB. This means the runway will be closer to AB than to AD if it’s on that side of the line. You may wish to shade one side of the line so you remember which way round it is. i always shade the side I DON’T WANT.
To ensure the runway is at least 800m from the canal:
- 1cm = 400m so 2cm = 800m. The runway must be 2cm away from the canal on the scale drawing.
- Measure 2cm away (perpendicularly) from the canal line. Do this three times and join the dots. This should form a parallel line which is 2cm away from the canal line. The runway must be behind this line (on the side away from the canal). Shade again to remind yourself.
If the runway has to be in an East-West direction, it must be completely horizontal.
The runway must be 2000m long. That is 2000/400 = 5cm long on the scale drawing.
Draw a 5cm horizontal line wherever it will fit inside the area you have secluded (closer to AB than AD and more than 2cm from the canal line). You may wish to use a protractor to ensure it is horizontal (180 degrees all along)/in an East-West direction.
I hope this helped somewhat! Perhaps use a revision guide or youtube videos to hell you understand the topic as they will have useful diagrams that are easier to understand than my words written down.
Good luck with the rest of your work