Auto level is an optical instrument which is used in along with a levelling staff to establish the relative heights levels of objects or marks. It is widely used in surveying and construction to measure height differences and heights of known objects or marks. It is also useful in construction of roads, to calculate CUT & FILL in a road project, deciding slope on side for draining purpose. It was invented by an English Civil engineer, William Gravatt in 1832.
It makes use of internal compensator mechanism that ensures that the line of sight remains horizontal once the operator has roughly leveled the instrument.
Parts of Auto Level:
- Base Plate: area that the automatic level attaches to on the tripod.
- Horizontal Circle
- Eyepiece: located at the viewing end of the telescope, it can be adjusted to bring the crosshairs into focus.
- Circular Bubble Tube: The bubble in the tube must be brought in the center in order to level the instrument.
- Gun point: to roughly line up with the staff before looking through the eyepiece.
- Objective Lens: It is kept towards the object (Leveling Staff) to receive rays into Telescopic Tube.
- Focusing Knob: It is used to focus the Staff in order to read the graduations.
- Tangent screw: it is used to rotate the telescope slowly.
- Levelling Foot screw: used to level the auto level.
- Bubble mirror: bubble from the tube is reflected on this mirror.
https://www.youtube.com/watch?v=73mquZh29Rwhttps://www.youtube.com/watch?v=K-oCUDUlQh8
SETUP AND LEVELLING:
Firstly, place auto level on the tripod, and fix the instrument onto the tripod base. After mounting your instrument, it is important to make sure it is level around all 360 degrees in order to allow for precise and accurate measurements. Firstly, adjust the leg length of the telescope to until the level bubble partially settles into the circle. Place the telescope in a position that is parallel to two of the three leveling screws. Turn both screws simultaneously in opposite directions and then adjust the third levelling screw until the bubble is centered in the circle. Once the bubble is centered, rotate the instrument 90 degrees and ensure the bubble returns to the circle.
How to take readings using an auto level:
After making sure your instrument is level, the next step is focusing the automatic level.
- The first step in this process is to aim your telescope at your staff. Adjust the eyepiece either left or right to make the staff appear clearer.
- After focusing the eyepiece, point the telescope directly at the specific target. While keeping the crosshairs in focus, use the focusing knob to make the specified object appear sharp.
- To take the reading one person should look through the eyepiece of the telescope while another person holds a staff vertical at the point under measurement.
- The height of instrument is found by taking a back sight to a staff placed on a bench mark. The staff reading is added to the benchmark value to obtain the height of instrument.
- Once the height of instrument has been found, ground height at any spot below this plane can be found by observing the staff and subtracting the staff reading from the height of instrument.
HOW TO READ AUTO LEVEL STAFF:
Full Foot numbers are given in red while one tenth foot numbers are given in black. Each black line between a whole foot number and one tenth of the same gives an even hundredth of that feet while a white line gives an odd hundredth of that feet. Each line is 0.01 ft apart.
https://www.youtube.com/watch?v=MsCmY9R-HCU
Advantages:
- Easy to use
- High accuracy
- Affordable
- The auto level has an internal compensator mechanism which automatically adjusts the line of sight.
Online purchase
Price of a good quality auto level normally ranges between 300-350 dollars in international markets while in Pakistan a used auto level can also be bought in a fairly cheap price.
https://www.amazon.com/Bosch-Automatic-Optical-GOL-32/dp/B00BCNH81S?ref_=fsclp_pl_dp_7
https://www.amazon.com/Leica-Geosystems-840386-Automatic-Optical/dp/B01BZYTY38?ref_=fsclp_pl_dp_6
https://www.engineersupply.com/automatic-levels.aspx
https://www.olx.com.pk/item/sokia-auto-level-iid-1002171800
Civil Gadgets. 
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