So as you can see we're out on the jobsite today, and the boss has asked us to
work out what level the ground is all the way around this job that we're currently building
so in order to
prepare these heights We have to have a point on a jobsite that we actually know the height of or has a designated height
That's referred to as the job datum. This is the mark for a datum realistically
it'd probably just be a nail or a mark on the curb or something else is not going to move
too often
and that'll be designated as your job datum and marked on the plans as such now
this could actually just be given a nominal height. It's normally a positive like 10 meters 20 metres or a 100 metres
That allows for readings to be taken below it without going into the negative numbers
or it could have an actual level above sea level height above sea level
If it's given a height above sea level then you need to get a registered surveyor to come in
What I'll do is they will have a look around the subdivision
and they'll be looking for a survey mark or an Australian Height Datum
This looks a bit like this, okay it's got a number on it and
the registered surveyors they can get onto the Spatial Information System
They can look up the position of this mark
and they can find out the longitude and latitude of it and the
Height above sea level and once they know the height above sea level of this
mark they can then transfer that down the road to our datum
However in this case I haven't done that I've just given this a nominal height of 10 metres
So this work on something to compare the other levels to
So we're going to then set up our instrument and get ready to start taking our levels we also need to set up our
Level book, so this is what they call a Rise and Fall level book there is also a Height of Collimation level book
However the process of filling them out and recording the readings
Is the same so I'll show you how to fill out this one same for height of collimation and later on in another video
I'll then show you how to calculate the rise and fall method and the height of collimation method
So with the level book first thing you need to fill out is the information
So the site that you're on just in case it goes off the site
the height of the Datum
which you know is 10 metres
This is going to be a closed
survey so we're going to go from the datum right around the house and back to the Datum and
it's done on the 23rd of
July 2003 so
great
That's some change that back to a date shall, we
Okay
So we know when the actual survey was taken
so that's how a sheet ready to go so now we can go back to the instrument and
It shouldn't set up we get our offsider. Oh, sorry the first other thing. We need to do is
Go around and number where we're going to take a reading so this case. we're just going to do at the bottom of each pier
Yes, now, I haven't got the endcaps or the DPC in
The object of this exercise we don't need it, so I'm done with all the piers
and
our offside is ready to go
when we know all the numbers of our positions we can actually go back here and
put those in our sheet, so we're going to start the datum then going to go position 1, 2, 3
It's 17 positions, and then we do the last one back at the datum. So that's where we going to take all our readings
Okay, let's start taking some readings
so I'll set up, old mate is here with the staff and
look through the instrument, thats my simulation of looking through the instrument, take a reading so 23, 2350
2390 about 2395
so we get back to our level book and
Because this is the first site that we've taken and it goes back to a known point
we're going to write it in the backsight column
and we're taking it from the Datum, so
2.395 that goes in there
Then we go back to our level
Get our off-sider with the staff to move the instrument here doesn't move it just rotates around
Take another reading
And this one's going to be
2.050
So to our little book
2.050
this is an intermediate sight and
It's taken from Position 1 so
the first readings always a backsight
Everything else is intermediate, and then we've set for the last one that we take which is a foresight
So the rest are going to go in the middle here, so position one
Intermediate sight in that position there
So there we go
get our mate to move to position to
Take our reading and we look at
1950, 60, 70
So back to our level book
1.970
and this is going to continue
we move
You take a reading you
put it in a little book
This is 1.888
Move take a reading
through the level book1.808
old mate moves, take a reading
put it in the level book
1.722
There's a bit of a process here because it's quite a few readings to do
1.664
Okay, I took all these readings before let's write up straight in
Oh, sorry one should be
1.609
this one is
1.534, Okay, so now we're up to the interesting part
Because this next reading is
Going to be the last reading that we can see
from this position so it's going to be what we call a foresight because we're taking this reading
looking forward to moving around the corner, so
This will be a foresight so the readings are same take the reading
go back to our level book and
this time it goes into the foresight column so that one
1.493 okay, so that's our first
section done now it has to happen is
The guy here with the staff he stays where he is and
our tripod and instrument moves
Old mate is still over here hiding behind the corner
Okay, he's going to move around but the instruments going to stay
essentially in the same spot
Also, the level is going to stay in the same spot instruments moved and then we're going to take a reading back to that staff
again
Okay, now what we do with that reading
It's a backsight because from this new position. It's going back to a known point
So we put our reading back in our backsight column
and
it's worth throwing over in our remarks Column, but that's a change point
pretty Obvious because it's going to the only spot with two readings on the line
but we can throw that in our marginal information or our remarks column
Okay, so then the process is the same
we go back to our staff and
Old mate moves up one
we take a reading
And we call that back now in our intermediate column
Again we move take the reading through the instrument
very important when you're doing this
to make sure that you are taking
accurate readings and
that you are recording those numbers accurately because if you don't when you go to actually check the
calculations on your on your
Level book and you get it wrong
it's going to mean that you need to go back out to the job site and do the survey again
which is not going to be good for art for anyone
Okay, let me just check i'm running out of. ao we are on this point fourteen
So what should be
Yeap, we are up to Point 14 to haven't lost track 2.052
oh should be a point
start talking about accuracy and start getting inaccurate yourself
So we keep moving around taking our readings
2.133
Couple more to go
2.216
So we're under our last point here. Take that reading
2.289, and then the last point as I said is going to be our
Datum, so you're back out of Datum. Take a reading on it and
It's our last reading on the datum. So it goes in our foresight column and it's a
2.634 so there we go. Sorry that should be a point. We've taken all our levels
We've recorded everything in our level book ready to do the calculations. Which I'll show you in the next video and
we're done all the levels are recorded so
that's the process of recording the levels and as I said in the next video
I'll show you how to calculate them and actually work out. What the difference is between
these points that we've just taken