Point List Duplicate and Gap Checker
Checks a survey point list for repeated IDs, integer ID gaps, coincident and near coordinates (exact, inclusive tolerance) and invalid rows — each as a separate report with its own CSV, and an optional Z rule for 3D duplicates.
Point list and checks
Repeated IDs, ID gaps, coincident and near points are reported separately. They are candidates to review, not records to delete.
Paste or open a point list, confirm the mapping and press Run check.
Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.
How to use this calculator
- Paste the point list or open the file, check the delimiter and header toggle, and confirm the ID, Easting and Northing (and optional height) columns in the mapping preview.
- Choose how IDs are compared, whether to report integer gaps, the coordinate units, an XY tolerance for near points and, if you want, a Z rule with its own tolerance.
- Press Run check and work through the separate reports: repeated IDs, ID gaps, coincident coordinates, near points and invalid records. Each has its own CSV download.
How it works
Repeated IDs use exact string comparison by default, so 0007 and 7 are different IDs (the gap report notes when two spellings share an integer value). A repeated ID with different coordinates is reported as a conflict, not a duplicate.
Gaps use only whole-number IDs, sorted as exact integers (BigInt), and are shown as compact ranges such as 3–4. Non-integer IDs are counted and skipped.
Near points satisfy √(ΔE² + ΔN²) ≤ tolerance, inclusive. The comparison is done on the decimal digits exactly, so a separation equal to the tolerance always qualifies (ordinary floating point puts 100.010 − 100.000 at 0.010000000000005, just over 0.010). A grid index on the tolerance avoids comparing every pair.
With the Z rule on, a pair counts as a 3D duplicate only when both heights exist and |ΔZ| ≤ the Z tolerance; a missing height is reported as not compared. Findings are candidates for review — coincident points can be different real features.
Worked example
IDs 1, 2, 2, 5. Point,Easting,Northing with rows 1 (1000.000, 2000.000), 2 (1010.000, 2000.000), 2 (1010.000, 2000.000) and 5 (1025.000, 2010.000) gives one repeated ID — 2, records 3 and 4, same coordinates — one coincident group, and the gap 3–4 (2 missing IDs). With a 0.010 m tolerance, points at 100.000 and 100.010 are a near pair; at 0.0049 m a 0.003/0.004 offset (5 mm) is not.
Frequently asked questions
Are leading-zero IDs different?
Yes by default: 0007 and 7 are different text, and many controllers treat them as different points. The gap report tells you when two spellings share the same integer value so you can decide.
Are gaps errors?
Not necessarily. Deleted points, reserved number blocks and merged jobs all leave gaps. The tool lists them so you can confirm none are missing by mistake.
Does coincidence mean duplicate?
No. A kerb and a pit can share a plan position, and a peg and its offset can sit at different heights. Coincident and near points are candidates to check, never an instruction to delete.
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.
Related tools
- Survey CSV Cleaner
- Point List Renumber Tool
- Set-out Upload File Validator
- Coordinate Import Template Generator
- Easting/Northing Distance Calculator
- Coordinate CSV Schema Builder
Explore more in Surveying, Coordinates, GIS & CAD.
Cite this tool
Zerdly. (2026). Point List Duplicate and Gap Checker. Retrieved from https://www.zerdly.com/tools/point-list-duplicate-and-gap-checker/
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.