Surveying 2 - Taking a level reading - OTEN Building & Construction

Summary

In the video, Dave, the OTEN Head Teacher, demonstrates level measurement techniques at Nirimba College. He introduces a five-stage aluminum staff, explaining its color-coded sections for extension verification. Dave highlights the importance of using a fiberglass staff near power cables for safety. He discusses the 'E pattern' graduation and the necessity of reading to the millimeter for accuracy. The process of taking a level reading is detailed, including ensuring the staff's cleanliness, holding it vertically, and interpreting the reading to three decimal places. The video concludes with a preview of a two-peg test for level accuracy.

Takeaways

• 🏫 The video is set at Nirimba College and features an OTEN Head Teacher, Dave, who is demonstrating surveying techniques.
• 👷‍♂️ Dave introduces a two-man process for taking readings using a levelling instrument, which is a common practice on construction sites.
• 🔍 The staff used is a five-stage aluminum staff, designed for durability and ease of use in surveying.
• 🔑 The staff has color-coded sections (black and red) to help the surveyor ensure that all sections are properly extended.
• ⚠️ Safety is emphasized with the mention of using a fiberglass staff near overhead power cables to avoid electrical hazards.
• 📏 The staff is graduated in an 'E pattern' and is used in conjunction with a measuring tape graduated to millimetres for precise measurements.
• 📐 Readings are taken to three decimal places, indicating a high level of accuracy required in surveying work.
• 🧐 The necessity of interpolating readings within 10-millimetre graduations on the staff is explained, requiring estimation skills.
• 👋 Proper staff handling techniques are demonstrated, including keeping the staff clean and holding it in a way that allows clear visibility of the graduations.
• 🔄 The importance of moving the staff vertically to ensure the most accurate reading is highlighted, as tilting can affect the reading.
• 📋 The video concludes with a reading of 1.372 metres, demonstrating how to locate this measurement on the staff.

Q & A

What is the purpose of the staff shown in the video?

The staff is used in conjunction with a level instrument to take accurate measurements, particularly for leveling tasks on construction sites.

How many sections does the staff have?

The staff is a five-stage staff, meaning it has five sections.

Why is the staff color-coded?

The staff is color-coded with alternating colors to help the person looking through the instrument identify which sections have been extended.

What material is the staff made of and why is it important?

The staff is made of aluminum, but for work near overhead power cables, a fiberglass staff is recommended to avoid electrical conductivity.

What does the 'E pattern' graduation on the staff signify?

The 'E pattern' graduation refers to the way the staff is marked with measurements, which is typically used in building sites for precise measurements.

Why is it necessary to read levels to three decimal places?

Reading levels to three decimal places, or to the millimeter, ensures the accuracy of measurements on site, which is crucial for construction activities.

How does the measuring tape help in taking readings from the staff?

The measuring tape, graduated to millimeters, is used to interpolate and estimate readings between the 10-millimeter graduations on the staff.

What are the three things to ensure when holding the staff for a reading?

When holding the staff, one must ensure the bottom is clean for an accurate reading, keep hands clear of the graduations for visibility, and wave the staff to find the vertical position for the lowest reading.

Why is it important to wave the staff during the reading process?

Waving the staff helps the person taking the reading to identify the lowest point, which corresponds to the vertical position, ensuring the most accurate measurement.

What is the reading obtained in the video and how is it located on the staff?

The reading obtained is 1.372 meters, which is located on the staff at the 1.37 meter mark, plus an additional two millimeters.

What is the next step after taking a reading that the video mentions?

The next step mentioned is to complete a two-peg test to verify the accuracy of the level's readings.

Outlines

00:00

📏 Demonstrating Level Measurement with a Staff

In this segment, Dave, the OTEN Head Teacher, introduces the process of leveling and taking readings using a surveying staff. He explains the features of a five-stage aluminum staff, including its color-coded sections for easy extension tracking and the importance of using a fiberglass staff near power cables for safety. Dave also details the 'E pattern' graduation of the staff, which is read in conjunction with a millimeter-graduated measuring tape for precise readings to three decimal places. He emphasizes the need for accurate readings by ensuring the staff is clean, held vertically, and waved gently to find the lowest reading. The demonstration concludes with a practical reading of 1.372 meters, showcasing the level of precision required in surveying work.

05:00

🔍 Upcoming: Two-Peg Test for Level Accuracy

The next segment teases a tutorial on conducting a two-peg test, which is a method used to verify the accuracy of level readings. This test is crucial for ensuring the reliability of surveying equipment and the precision of construction projects. The anticipation is set for a practical demonstration that will likely involve comparing readings from two different points to confirm the level's calibration and performance.

Keywords

💡Staff

A 'staff' in the context of the video refers to a measuring tool used in surveying and leveling work. It is a graduated rod that helps in taking precise measurements. The video explains how to properly extend and use the staff for accurate readings. The staff is a five-stage aluminum rod, with alternating color sections to ensure correct extension and readability.

💡Leveling

Leveling is a surveying method used to establish a known elevation or height relative to a known reference point. In the video, the process involves using a level instrument and a staff to measure elevations accurately. The term is central to the video's theme of demonstrating how to take precise measurements on a construction site.

💡Graduated

When an object is 'graduated,' it has marked divisions or units that allow for precise measurement. The staff in the video is graduated in an 'E pattern,' which is a common design for measuring tools in surveying. The graduations help in reading measurements to the millimeter, which is crucial for the accuracy required in construction work.

💡Millimetre

A 'millimetre' is a unit of length in the metric system, equal to one thousandth of a meter. The video emphasizes the importance of reading measurements to the nearest millimetre for accuracy in construction leveling. This level of precision is necessary for ensuring that structures are built level and plumb.

💡Aluminium Staff

An 'aluminium staff' is a type of measuring staff made from aluminum, a lightweight and durable material. The video mentions that while aluminum is suitable for general use, a fiberglass staff should be used near overhead power cables to avoid conductive risks. This highlights the importance of material choice based on the work environment.

💡Fibreglass Staff

A 'fibreglass staff' is a non-conductive measuring tool used in situations where there is a risk of electrical hazard, such as near overhead power lines. The video suggests using a fiberglass staff for safety reasons, indicating an awareness of safety protocols in different surveying scenarios.

💡E Pattern

The 'E pattern' refers to a specific graduation style on a measuring staff, which is designed to facilitate easy reading of measurements. The video explains that this pattern is used on building sites for taking measurements with precision, aligning with the theme of accuracy in construction surveying.

💡Interpolation

Interpolation is the process of estimating values between two known points. In the video, the term is used to describe how to estimate readings between the 10-millimetre graduations on the staff. This technique is crucial for achieving the required level of accuracy in the measurements taken.

💡Vertical Position

A 'vertical position' refers to the orientation of an object being perpendicular to the ground. The video instructs on holding the staff in a vertical position to ensure accurate leveling readings. The importance of this concept is highlighted by the need for the staff to be held straight to get the lowest and most accurate reading.

💡Two-Peg Test

A 'two-peg test' is a method used to verify the accuracy of a level instrument. The video teases that the next demonstration will involve this test, suggesting a systematic approach to ensuring the reliability of surveying equipment. This test is a practical example of quality control in construction surveying.

💡Crosshair

A 'crosshair' is a set of intersecting lines, often used in the sights of instruments like levels, to help align and focus on a specific point. The video mentions that the crosshair will give a higher reading if the staff is not held vertically, indicating its role in precise measurement and the need for correct staff positioning.

Highlights

Introduction to the staff and its use in taking readings from a leveled instrument.

Demonstration of the two-man process for using the staff on site.

Explanation of the five-stage staff and its color-coded sections for proper extension.

Safety consideration for using an aluminium staff near overhead power cables.

Advisable use of a fiberglass staff for safety near electrical hazards.

Description of the staff's 'E pattern' graduation and its relevance to building site measurements.

Importance of accuracy in measurements, with levels taken to three decimal places.

Interpolation method for estimating readings within the 10 millimeter graduations on the staff.

Technique for ensuring an accurate reading by cleaning the bottom of the staff.

Guidance on holding the staff to allow clear visibility of the graduations.

Method for determining the vertical position of the staff by waving it.

Explanation of how to identify the lowest reading when the staff is in the vertical position.

Practical demonstration of taking a reading with the staff and telescope.

Identification of the reading on the staff and its precise location.

Overview of the accuracy order, staff graduation, holding technique, and reading process.

Preview of the next topic: completing a two-peg test to verify the accuracy of level readings.

Transcripts

♪ (upbeat music throughout) ♪

We're at Nirimba College with OTEN Head Teacher, Dave.

What are you going to be showing us next?

Jason, I'm going to introduce you to the staff

and how to take a reading to it from the instrument we've just levelled.

This is normally a two-man process on site.

Would you like to give me a hand?

Love to, bring it on!

Jason, I now just want to show you some features of the staff.

If you could just lower that down for me...

This staff is a five-stage staff,

so it has five sections to it.

And you'll notice, if you wouldn't mind extending that out now,

as you raise it up, it actually needs to clip in here at the back,

and that clip is on each section of the staff.

Also, you'll notice that the first section is in black, second section is red,

it alternates up the staff,

so that the person looking through the instrument

can see that we've actually extended,

in this case, the first and the second section.

So, that's just to check to make sure that we've extended the staff properly.

Second thing is, this is an aluminium staff.

If we were working near overhead power cables,

it would be advisable that we were using a fibreglass staff,

just in case we did contact those overhead wires.

Next, this staff is graduated in what we call an 'E pattern'.

And on building sites,

we tend to take a lot of measurements with this measuring tape.

The tape is graduated to millimetres

and that is generally the order of accuracy that we expect on most...

activities on site.

No different to reading levels.

We actually take levels in metres,

but to three decimal places.

So, we're getting down to the millimetre.

Unfortunately, the staff is only graduated to 10 millimetre sections.

If we place the measuring tape on the staff,

we can see that, for instance, here that line there

is actually 800 millimetres, or 0.800 metres.

These 10 millimetre blocks mean that is a reading of 0.810, 0.820,

0.830, 0.840, 0.850,

-60, -70, -80 -90, till they get to 0.900.

I've said we need to read to the third decimal place,

so we actually need to interpolate, in other words, estimate,

at what section, or what millimetres we are reading,

when we're in one of these ten millimetre blocks.

If we're in the middle, that's quite easy.

If we're in the middle of that section,

that would be 0.8, 0.85, 0.855.

Okay Jason, let's go take a reading,

but before we do, I'll just make you aware of a couple of things.

First off, I need you to make sure the bottom of the staff is clean,

so that I'm getting an accurate reading.

Secondly, when you're holding the staff, that's lovely, keep your hands clear

of the place of the staff, so I can see all the graduations,

and thirdly, I'm going to get you to wave the staff,

rock it just forward and back of vertical.

I will know when you're in the vertical position,

that will be my lowest reading.

Because when you lay back, or lay forward,

my crosshair will give me a higher reading on the staff.

You may not be holding it in the vertical position

if you just hold it like that,

and I can't tell if you're leaning forward or leaning back,

so by slowly waving the staff,

I will know the lowest reading is the one I'm after.

Now we're going to take a reading to the staff.

Jason's placed the staff on a peg that I want to get the level of,

so I'm going to look through the telescope and obtain that reading.

Jason's going to wave that staff a little bit for me.

And I will know the lowest reading is the one I'm after.

And my reading is...

1.372.

So, I'd just like to show you now where that reading is on the staff.

It's about there on the staff.

1.3...

1, 2, 3, 4, 5, 6, 7...

and two millimetres.

1.372.

So, what we've just seen here is the order of accuracy,

the staff graduation,

how to hold a staff,

and how to take a reading.

What are we going to see next?

Jason, next time I'm going to show you how to complete a two-peg test

to check that the level's giving us accurate readings.