G'day welcome back to Buildsum so we've completed our grid survey on our block of land
Got our R.L. points all drawn or written in now we actually can go about plotting where our contour is going to be so
Firstly we need to know what contour intervals we need
So I'm going to use half a meter contour intervals so obviously
obviously starting at 0
Half a meter, one meter, so on so we'll start with our half a meter contour line
So I'm going to have a look for the two points where that's going to go through and obviously it's going to go between
100 and
800 so this is where I want to start
my
Plotting my contour lines so first thing
I need to know is the difference between these two points and just to keep it in positives. We'll take this point here, so
2nd RL minus the first RL will give it 700 so there's a 700mm
difference in height between those two points
Next thing I need now is the grid line length, so how far apart are these lines on my scaled plan
There are about what you did when you marked the site out on your scaled plan how far apart are they
and on this one they're 10mm apart
So what we do is we take that 10mm and we divide it by our difference
Or 0.700 in this case
that gives us 14.285 so that tells us is how far apart a
Metre would be
In this particularly grid square or this particular square
okay, doesn't have much relevance to it to us at this point, but that's what we need that 14.285
so now what we want to know is the difference between our first, RL this hundred here and
The RL that we actually need or the contour interval. We need which is the 0.500
in this case that's
400mm, 0.4 and
we times that by the 14.285 that we got here and that gives us 5.714
So that 5.714 is the number of millimeters that it is from this first RL
to where our
0.500 contour line will cross this line
so you can measure 5.714 and
put a mark on our line there
so now it's just a matter of pretty much repeating the process
We'll go and have a look at the next two so 0.500
It's not going to cross that line. It's going to cross between these two points, so
0.53 minus 100 gives us a difference of 0.430
We know that our contour line is 10mm
so we can divide the 10mm by the 0.430 and that gives us a difference or a
figure of 23.256
and then
difference between our first RL in a contour RL is
400mm and
400mm times 23.256
Gives us 9.302 millimeters from here down to where our contour lines going to cross
And we can put a mark there as well for that. I have got a little excel type calculator
I'll put the link over the video here somewhere and
If you want to use that rather than what is that the calculator you're welcome to use that
so the next step obviously
0.500 is going to come between these two somewhere
so again
Second RL minus our first RL. Gives us a difference of 0.440
You know again this is 10mm divided by 0.440 gives us 22.727
0.09
0.5 which is our RL
Sorry our contour line RL gives us 0.410
0.410 time's our 22.727 gives us 9.318
And we can put a mark there
So hopefully you'll see it starting to see the pattern so now find the next two lines. It's going to be these two
Find the difference
work out that figure there
and work out how many millimetres it is, in this case 3.412
mark that
put a little mark on our drawing and we got one last one to do is going to cross out of the site here, so
do the same procedures for our calculations go with that
And we get 8.05
So now we've plotted all the points for our first, RL
first contour line
We can draw
Just straight Lines between those
So that's going to give us a rough idea of where our contour line will run obviously contour lines aren't straight
so we can use a bit of poetic license or
artistic license, I should say and we can just curve that line around to give us a
more realistic
shape of the ground
That's our first line then we have to plot our second the contour line
Which is at a metre so it's going to go between these two
It will come down between this one
between here
it'll
Come between this one
It will come somewhere between here
somewhere here and
Yes, you get the idea. I'm not going after all the calculations again, but that's roughly what it looks like
and
similarly for our third contour at one point five metres and
our
fourth contour at two metres and
Our last contour at 2.500 metres
So I was starting to see a little bit of a high point in this corner of the site
So there you go that's how we can use our grid survey to develop the contour lines on our site plan