Level Difference Calculator
Calculate height differences between two points using elevation and BS/IS readings.
How This Tool Works
Purpose:
This tool allows you to calculate the height difference between two points using the elevation (RL) and staff readings such as Back Sight (BS) and Intermediate Sight (IS).
How It Works:
- Enter known elevation (RL) of Point A
- Add BS or IS reading
- Input the reading for Point B
- The calculator determines the height of collimation and then the elevation of the second point
- The output shows the level difference between the two points
Note: Useful for quick levelling checks on-site when using a dumpy level, auto level, or digital level.
Enter Known Data
Point to Calculate
Your calculated level difference and elevation will appear here.
Height of Collimation
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Point B Elevation
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Level Difference (A to B)
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Fast, Accurate Level Calculations for On-Site Surveying
Designed for construction engineers, surveyors, and setting-out professionals.
Frequently Asked Questions
You need the known elevation (RL) of your starting point, a Back Sight (BS) or Intermediate Sight (IS) reading from that point, and the staff reading at the point you want to calculate.
A Back Sight is the first staff reading taken when setting up your level instrument. It's read on a point of known elevation to establish the height of collimation.
An Intermediate Sight is a staff reading taken on points between the back sight and fore sight. It's used to determine elevations of intermediate points without moving the instrument.
Height of Collimation = Known Elevation + Back Sight reading. This represents the height of the line of sight of your level instrument above datum.
Use this tool for quick elevation checks, setting out levels, checking gradients, or when you need to calculate height differences between survey points during construction or surveying work.
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