Control Mark Description Generator
Builds a structured field description for a survey control mark — identity, access, reference systems, coordinates and their source, condition and cautions — keeping values exactly as typed and showing anything unknown as Unknown.
Mark details
Values are kept exactly as typed. Blank fields print as Unknown. No coordinate is transformed and no datum is assumed.
Enter the mark ID — the record cannot identify the mark without it.
Formatting does not establish a mark's stability or the accuracy of its values. Use the authoritative control record for adopted values.
How to use this calculator
- Enter the mark ID and whatever you know: type, material, how to find it, the horizontal CRS and epoch, coordinates and where they came from, the vertical datum and RL, the reference source, condition and cautions.
- Read the warnings — coordinates with no CRS, an RL with no vertical datum, a coordinate source not stated — and the mark card.
- Edit the formal description if needed, then copy it, download it, print a field card or export JSON (an attached photo is only embedded if you choose).
How it works
The description is assembled in a fixed order — identity, location and access, reference systems, coordinates and source, condition, cautions — so every record reads the same way.
Values are kept exactly as typed: ID001 stays ID001 and 391234.5600 keeps its trailing zeros. Easting, northing and RL are only checked to be plain decimal numbers; negative RLs are valid. Nothing is rounded, transformed or given an assumed CRS.
Blank fields print as Unknown in the formal record rather than disappearing or being filled with a default. An RL without a vertical datum is printed “Unreferenced”, and handheld-GNSS or map-read coordinates are labelled navigation-only, separate from control values.
The output is a field description prepared from your entries. It does not establish a mark's stability or the accuracy of its values and is not an official control certificate.
Worked example
ID001 with an RL but no datum. Mark ID001, nail in kerb, GDA2020 / MGA zone 50, epoch 2020.0, E 391234.5600 N 6450123.0400 derived by survey on the job, RL -1.250 with no vertical datum. The record keeps every digit, prints “RL: -1.250 (Unreferenced — vertical datum unknown)” with a !! RL UNREFERENCED flag, and shows “Recorded by: Unknown” because that field was left blank.
Frequently asked questions
Can I use this as official control?
No. It formats your own field description. Adopted control values come from the authoritative record for the mark, and lodging or registering a mark follows your jurisdiction's process.
How do I record an unknown datum?
Leave the field blank. It prints as Unknown, and an RL without a vertical datum is flagged Unreferenced so nobody assumes AHD or any other datum.
Are coordinates transformed?
No. Coordinates and RL are stored exactly as typed, with the CRS and epoch you enter. No conversion between datums or projections is done.
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). Control Mark Description Generator. Retrieved from https://www.zerdly.com/tools/control-mark-description-generator/
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.