Surveying 1 – Introduction to leveling


♪ (upbeat music throughout) ♪ Hi, I’m Jason from OTEN,
Western Sydney Institute, the largest provider of online
and distance education and training for TAFE New South Wales. OTEN has created a series
of ‘How To’ videos on site surveying, using a level. Today we’re at the [Narimba Campus], demonstrating the use of a level
with headteacher David. – How are you, Dave?
– Hi, Jason. So, what are we going
to be going through today? Jason, today I’m going to demonstrate
the setup and use of the automatic level, commonly used on building sites. Great, well I’ll leave you to it then! Thank you. Ok, the automatic level
is one levelling instrument used on a building site. And there’s basically
three components in its use. There’s the automatic level itself, the tripod on which it sits, and when we take a reading,
that’s to the staff. I’m now going to demonstrate
the setup of the level and first we’re going to place the tripod. Tripods come in two types. Firstly, there’s this one,
the dome top. And there’s also a flat top. With the automatic level,
we generally use a dome top tripod. The tripod legs have to be placed
firmly in the ground and we try and keep
the top of the tripod level. The instrument’s then removed
from its case, and placed on top of the tripod. And it’s fixed by a screw from underneath. So, we can level the instrument
using the dome top by loosening the screw
and moving it over the dome top, until the bubble is in the middle
of the circle. In the event we can’t level it
on the dome top, then we have to use the levelling screws. To do that, we need to place the axis of the telescope parallel
to the line between two levelling screws. Then by turning the levelling screws
both in, or both out, never in the same direction, we bring the bubble adjacent
to the centre of the circle. We then rotate the instrument
90 degrees, and use the third levelling screw to bring the bubble
into the middle of the circle. We can then check
just by rotating the instrument around through a few locations, to check that the bubble
remains in the circle. These are the features
of the automatic level. First we have the telescope, which contain the optics
for the level. The eyepiece, which we view through, and within those,
we have some crosshairs. This is the focus screw,
to bring our target into focus. And here we have a fine adjustment
or fine tangent screw, to make very small adjustments
to the direction of the level. Sitting on here we have the bullseye level
which we level the instrument to. And here we have a prism, which allows us to view
that bullseye target from the horizontal direction. The automatic level is a sensitive
piece of equipment which must be cared for. The instrument can’t be dropped, and must be transported in its case,
well secured. When setting up the level, ideally you will set it up at eye-height,
not as I’m demonstrating now where I have to stoop down
to read through the level. When moving around the instrument, be careful not to place any pressure
or put your weight on the tripod legs. This will push the level
out of adjustment. And when moving around the tripod,
make sure we don’t trip over the legs. And even placing pressure on soft ground
adjacent to one of the legs may cause the instrument
to go out of level. Thanks, Dave. So, what we’ve just seen
is setting up the tripod, placing the instrument, and then leveling the instrument. So, what are we going
to see next, Dave? Jason, now I need to show you
how to take a reading through the instrument.

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