How to Use an Auto Level on Site (Step-by-Step Guide)

Introduction

An auto level (also called dumpy level or optical level) is one of the most common instruments on Indian construction sites. Site supervisors and masons use it to transfer heights, level foundations, and check slab levels. This step-by-step guide shows you how to use it correctly.

Related tools: Staircase Calculator, Cement Calculator, BBS Generator, DPR Reports.

What You Need

• Auto level (dumpy level)
• Tripod
• Staff (levelling rod) – 4m or 5m
• Pen and notebook or phone app to record readings

Step 1: Choose the Instrument Position

1. Place the tripod roughly between the known point (benchmark) and the new point where you need the height.
2. Keep the tripod legs stable and roughly equal distance from the centre.
3. The instrument should be able to see both staff positions clearly.
4. Key point: Distance from instrument to both staffs should be roughly equal to minimise errors.

Step 2: Set Up the Tripod

1. Push tripod legs firmly into the ground (or on firm surface).
2. Open the tripod head so the instrument plate is roughly horizontal.
3. Mount the auto level on the tripod and tighten the screw.

Step 3: Rough Leveling

1. Rotate the instrument so two of the three foot screws are in line with each other.
2. Turn both screws in opposite directions to centre the circular bubble.
3. Rotate 90° and use the third screw to centre the bubble again.
4. Check: Rotate 360°. The bubble should stay centred. If it drifts, repeat.

Step 4: Take a Backsight (Known Point)

1. Place the staff vertically on the benchmark (known height point).
2. Look through the eyepiece and focus on the staff.
3. Read the middle crosshair on the staff (e.g., 1.450 m).
4. Note: This is your backsight (BS) reading.
5. Instrument Height (IH) = Benchmark height + BS
   Example: BM = 100.000 m, BS = 1.450 m → IH = 101.450 m

Step 5: Take a Foresight (New Point)

1. Move the staff to the new point where you need the height.
2. Sight the staff through the auto level.
3. Read the middle crosshair (e.g., 2.100 m).
4. Note: This is your foresight (FS) reading.
5. New point height = Instrument Height - FS
   Example: IH = 101.450 m, FS = 2.100 m → New height = 99.350 m

Step 6: Multiple Points (Profile Leveling)

To find heights at several points from one setup:

1. Keep the instrument in place.
2. Take backsight once (on BM).
3. Take foresight on each new point.
4. Record each reading.
   Height of point = IH - FS (for that point)

Common Mistakes to Avoid

Mistake	Why it matters
Staff not vertical	Reading is wrong. Use staff bubble or ask helper to hold plumb.
Unequal distances	Instrument error (collimation) affects result. Keep BM and FS distances roughly equal.
Bubble not centred	Line of sight is not level. Always check before each reading.
Wrong reading	Middle crosshair, not top or bottom. Double-check.
Forgetting BM height	Always note benchmark height clearly in your book.

Key Points

• Backsight = reading on known point. Foresight = reading on new point.
• Instrument height = BM + BS. New height = IH - FS.
• Keep distances from instrument to both staffs roughly equal.
• Record all readings in a field book or app (e.g., Yojo DPR with site notes).

Summary

1. Set tripod, mount level, centre bubble in all directions.
2. Take backsight on benchmark → calculate instrument height.
3. Take foresight on new point → new height = IH - FS.
4. For multiple points, take one BS and many FS from same setup.
5. Record everything. Use DPR to document site levels and progress.

For slab work, see Step-by-Step Slab Casting Checklist. For site management, use Yojo contractor app.