Spot Height to Contour Practice Tool
Practises linear interpolation to find where a contour crosses between two spot heights.
Practice question
Generating a question…
How to use this calculator
- Read the two spot heights, the distance between them and the contour interval.
- Work out how far along the line the named contour crosses, then reveal the answer.
- Generate a new question to practise as many as you like.
How it works
Between two spot heights the ground is assumed to slope evenly, so the contour crossing is a straight-line (linear) interpolation.
Distance from A = length × (contour level − RL at A) ÷ (RL at B − RL at A).
Worked example
14 m contour between 12 m and 16 m. A = 12.0 m, B = 16.0 m, 20 m apart. The 14.0 m contour is halfway up the rise, so it crosses 10 m from A.
Frequently asked questions
Why assume an even slope?
Between two surveyed spot heights you have no information about the shape in between, so linear interpolation is the standard assumption for drawing contours.
Is this official course material?
No. It is free study support mapped to surveying course levels — not official North Metropolitan TAFE content or advice. Always follow your lecturer and the official assessment brief, and check your own working.
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Cite this tool
Zerdly. (2026). Spot Height to Contour Practice Tool. Retrieved from https://www.zerdly.com/tools/spot-height-to-contour-practice-tool/
Tip: Enter any known values to calculate the remaining results.
Designed to run locally in your browser. Tool inputs are not intentionally stored by Zerdly unless stated otherwise.