So in the last video we took some readings around this building and we recorded them on
our level book and
As I said before this is a rise and fall level book
So what I want to show you in this video is how we take these
seemingly
random figures and
Actually get something we can actually use out of them, so
The process is what we do is
this first figure here, we take away the second figure and
If the answer is a row our positive figure
It goes in the rise column if it's a negative figure it goes in the fall column
So 2.9Sorry 2.395 minus 2.050
is going to give us
0.345 that's a positive, so it goes in the rise column
Next step we take 1.970 away from 2.050
So that gives us
0.080mm difference again a positive test on the rise column
1.970 minus 1.888
Gives us a difference of 82mm, it's still positive so
0.082
1.888 minus 1.808
gonna give us a difference of 80 mil or 0.080
Still a positive test on the rise column
Keep working our way down. We end up difference of 86mm here
Next one's a difference of 58mm
and
1.664 - 1.690 it's going to give us a difference of 55mm
and
The next one is the difference of 75mm, 0.075
Now when we get to here, we do this one
minus this one which is in the first set of readings, so 1.534 - 1.493
gives us a difference of 41 millimeters
Okay, so now it gets a little bit tricky because this is our change point. So now we forget about these figures
We're just going to switch over and start back here
use this figure and take it away from also take this figure away from this figure here, so
1.732- 1.795
That will give us a negative. This is number here. This is bigger than this number. There's a negative of
63mm so because it's a negative
It goes in the fall column so 0.063
and
We keep working our way down, so this one minus this
Gives us a negative again of 64mm
Okay
So that minus that gives us a negative of 77mm
That one if that gives us a negative of 76mm
That minus that is this a negative of 40mm
That line us that is just a negative of 81
that one if that is this a negative of 83
All the negatives in the fall column and that one is that gives us a negative of 73mm
0.073 and that one is that gives us a negative of
345mm so 0.345
Okay, so there's all our initial looking at done. So we knows which ones are rising
Which ones are falling now we can do a quick check just to make sure we're on the right track, so
First two checks we can do
We can add these two up
So one 2.395 plus 1.732gives us
4.127
We can add these two up
1.493 and 2.634
It also gives us
Right about that one
that also gives us 4.127
Which is what we wanted actually sorry there should be up there
Where is it
cut slip in there
some old
formulas coming back
so those two are the same so the difference between those is obviously zero
Which is what we want because this is a closed survey
And we started at the same point that we finished the difference in elevation over the total
survey should be Zero
That's good. So the next thing we can check is our rise and fall, so if we add up all
these
We actually come up with
0.902 so over the total survey we had a rise of 902mm, and if we add up all the falls
Don't worry about the fact that they're negatives just add them up as if they were positives
We had to end up with a 0.902
difference as well
Which is good because then the difference for that one is zero so that's fine
So so far we've got zero for those two at zero difference on these two
zero, they're
the spreadsheets not showing zeros so it's disappearing and
That's what we want. So everything is right so far. So now we actually get what the actual height is
So we knew what the RL was 10 metres at the start
Well the datum was 10 metres
We have that written on a sheet. It was also on the site
So now what we have to do anything in the rise Column gets added
Everything in the fall column gets taken away
so 10 plus
345 is obviously going to be 10.345, so that's the RL of
our station or one now what we do is take our 10.345 and
Add the next line down to add 80mm
So that's going to become
10.425
so then again 10.425 plus
another 82mm t's going to give us 10.507
10.507 plus
80mm is
10.587
10.587n plus 86 is going to be ten
10.673
10.673 + 58mm is
10.731
10.731 plus55 is going to be 10.786
and we plus 75 it's gonna be
10.861
plus 41
it is
10.902
Which is good because 902 that was our total rises now this next one is
in the full Column so 10.902 minus
63 is going to give us ten point eight
10.839 and
minus 64will give us 10.775
10.775 minus
77 will give us
10.698
10.698] - 76
equals
10.622
Take away 40 equals
10.582
Take away 81 is going to give us
10.582
10.582 - 83
give us
10.418
minus 73 will give us
10.345
10.345 -
0.345 will give us 10m
which is good because that is back to our datum, and we know that the RL Datum was 10 meters
so the difference between our first RL and our last Rl is zero the spreadsheey or our level book works out and
It is correct and our survey is accurate
So that's how we use
a levlebook to look at our level so now we know that
Point 3 for example is
507mm higher than our datum or
Point 9 is 902mm higher than our datum
Okay, so that's the usefulness of a level book
remember the three checks add up your back sights add up your fore sites and work out the difference
add up your rises it up your falls work out the difference and
Your first RL and the last RL work out the difference of those
if you've done a closed survey, so you started at the same point and
Finished then your difference should be zero if you didn't do a close survey
Doesn't matter just that you'll have a margin of difference
But that Margin of difference should be the same for the first check
the second check and the third check should be the same difference that way that the
The level Book will still be accurate
So there we go that's how we use a rise and fall little book to work at our levels in the next video
I'll show you how to use the height of collimation
Level book to work out the same figures