Verification record · 19 August 2026
UTM ⇄ Lat/Long Converter:
Accuracy Verification
The Bearing Technology coordinate converter, checked against the international standard implementation and against the United States Government survey agency.
- Item verified
- utm-convertor.html
- Published at
- bearingtechnology.biz
- Build size
- 322,747 bytes
- Build SHA-256
- 2F07C696…8607CA77
- Projection method
- Krüger series, 6th order
- After Karney
- J. Geodesy 85(8), 2011
Result
Agreement with both authorities
Two independent references were used. The first is the reference implementation of the EPSG geodetic dataset; the second is the conversion service operated by the US National Geodetic Survey. The converter was tested as published — the same file the website serves, matched by hash before testing.
International standard
PROJ 9.5.1 / EPSG
0.00001 mm
Largest disagreement across 4,500 test points — ten nanometres, which is floating-point noise rather than a real difference.
US Government survey agency
NOAA / NGS — NCAT
20 / 20 identical
Every test point matched NGS to the last digit NGS publishes, both in the engine and end-to-end through the tool itself.
Logarithmic scale. Everything measured sits at or below the one-millimetre line that the published accuracy claim rests on.
Reference 1
The international standard — PROJ / EPSG
PROJ is the reference implementation of the EPSG Geodetic Parameter Dataset and is the engine underneath QGIS, PostGIS, GDAL and most commercial GIS software. Test points were generated across the entire UTM domain and converted both ways.
| Coverage | Extent |
|---|---|
| UTM zones | all 60 |
| Latitudes per zone | 15, from 80° S to 84° N |
| Longitudes per latitude | 5, centre to 2.9° off-axis |
| Hemispheres | both |
| Total points, each way | 4,500 |
| Direction | Largest difference | Points within 0.001 mm |
|---|---|---|
| Lat/Long → UTM | 0.0000079 mm | 4,500 / 4,500 |
| UTM → Lat/Long | 0.0000103 mm | 4,500 / 4,500 |
Worst cases occur where the projection is hardest — near the equator at 2.9° off the central meridian, in zones 52 and 39.
Reference 2
The US Government survey agency — NOAA / NGS
The National Geodetic Survey defines and maintains the US national spatial reference system. Its NCAT service was queried live over the NGS public interface. Both sides were set to NAD83(2011) so that no datum transformation occurred and the projection mathematics alone was compared; the converter was set to the matching GRS 1980 ellipsoid.
| Check | Points | Result |
|---|---|---|
| Converter engine vs NGS | 20 | 20 / 20 identical |
| End-to-end through the tool | 20 | 20 / 20 identical |
| Inverse compared with NGS inverse | 13 | 0.0104 mm max |
Test points spanned eight US sites including Alaska and Hawaii, plus India, the United Kingdom, Japan, Australia, South Africa and Chile, the equator, and 70° north and south.
Worked example — a Bearing Technology field point
| Source | Easting (m) | Northing (m) |
|---|---|---|
| Input latitude / longitude | 28.504480949° N, 77.185414739° E — zone 43 | |
| NOAA / NGS NCAT | 713,894.918 | 3,155,035.713 |
| BTPL converter | 713,894.918 | 3,155,035.713 |
Field cross-check
Against a GNSS rover and commercial software
Beyond the two authorities, 197 points from a Chhatarpur survey were used, captured with a CHC Navigation i73+ GNSS rover and converted independently in Global Mapper Pro and eSurveying. Figures below are the largest disagreement with Global Mapper across the set.
| Package | Max difference vs Global Mapper | Max difference vs GNSS rover |
|---|---|---|
| BTPL converter | 1.5 mm | 0.6 mm |
| eSurveying | 3.1 mm | — |
| Global Mapper Pro | — | 6.2 mm |
The residual millimetre or two is the rounding in the reference sheets themselves; at this level all three packages agree.
Scope
What this record does and does not cover
This record applies to the build identified above, verified 19 August 2026. An earlier build rounded results to six decimal degrees before display, which limited output to roughly 56 mm regardless of how exact the underlying mathematics was. That rounding was removed in this build, and the figures here were measured after the change.
- Projection only. No datum transformation is applied. Coordinates must already be referenced to the datum selected in the tool.
- Ellipsoid parameters are taken verbatim from the EPSG Geodetic Parameter Dataset, not from any secondary source.
- NGS publishes UTM to the millimetre, so the comparison against it cannot resolve finer than that. Agreement is exact to every digit NGS prints.
- The UTM domain is 84° N to 80° S. Outside it the tool warns and UPS should be used instead.
- Displayed precision is selectable up to 10 decimal places on degrees and 6 on seconds; the conversion itself always runs at full precision.