Open method tests
Reproducible results for area, distance, coordinate conversion and nautical routes.
These tests run the same calculation code as the public tools. They isolate specific assumptions and show reproducible results, not a certification of map accuracy. The test protocol was reviewed on 13 September 2026.
Download all 20 results (CSV)01 / Area and point density
A 100 metre radius circle centred at latitude 59.3293, longitude 18.0686 is approximated with equally spaced points. The flat-circle reference is π × 100² = 31,415.93 m². Sparse points cut across the curved boundary. The spherical polygon calculation can also differ slightly from the flat reference.
| Points | Measured m² | Missing m² | Underestimate % |
|---|---|---|---|
| 4 | 20,000 | 11,415.93 | 36.34 |
| 8 | 28,284.27 | 3,131.66 | 9.97 |
| 16 | 30,614.67 | 801.26 | 2.55 |
| 32 | 31,214.45 | 201.48 | 0.64 |
| 64 | 31,365.48 | 50.45 | 0.16 |
02 / Distance around a bend
A 90° arc with a 1,000 metre radius is measured with increasing numbers of straight segments. The reference is π × 1,000 / 2 = 1,570.8 m. Endpoints alone cut across the bend.
| Points | Segments | Measured m | Underestimate % |
|---|---|---|---|
| 2 | 1 | 1,414.21 | 9.97 |
| 3 | 2 | 1,530.73 | 2.55 |
| 5 | 4 | 1,560.72 | 0.64 |
| 9 | 8 | 1,568.27 | 0.16 |
| 17 | 16 | 1,570.17 | 0.04 |
| 33 | 32 | 1,570.64 | 0.01 |
03 / Coordinate round trips
Six WGS84 locations are converted to SWEREF 99 TM (EPSG:3006) and back, using the tool's rounding. The offset is the distance between the original and returned WGS84 points. A small round-trip offset demonstrates consistency, not independent positional accuracy.
| Location | Latitude | Longitude | Easting m | Northing m | Round-trip offset m |
|---|---|---|---|---|---|
| Malmö | 55.605 | 13.0038 | 374,243.76 | 6,163,926.55 | 0 |
| Göteborg | 57.7089 | 11.9746 | 319,758.02 | 6,400,326.04 | 0 |
| Visby | 57.6348 | 18.2948 | 696,685.54 | 6,392,831.26 | 0 |
| Stockholm | 59.3293 | 18.0686 | 674,571.87 | 6,580,743.01 | 0 |
| Umeå | 63.8258 | 20.263 | 758,803.44 | 7,088,280.8 | 0 |
| Kiruna | 67.8558 | 20.2253 | 719,583.12 | 7,536,069.97 | 0 |
04 / Sea route and speed
The public Stockholm sample route contains 14 waypoints. The same geometry is calculated at three speeds. Speed changes the estimated time, not the route distance. No assessment of navigation safety is made.
| Knots | Nautical miles | Kilometres | Minutes |
|---|---|---|---|
| 5 | 1.71 | 3.18 | 20 |
| 7 | 1.71 | 3.18 | 14 |
| 12 | 1.71 | 3.18 | 8 |
Sample waypoints (latitude, longitude)
- 59.31543, 18.0168
- 59.31567, 18.01707
- 59.31634, 18.01797
- 59.31664, 18.01772
- 59.31734, 18.01584
- 59.31775, 18.01473
- 59.3217, 18.01182
- 59.32237, 18.01323
- 59.32318, 18.01589
- 59.32373, 18.02451
- 59.32428, 18.03198
- 59.32395, 18.04086
- 59.32332, 18.04537
- 59.3213, 18.05039
Test data licence
Kalkylkartan's own result rows in these four tables and their CSV export are licensed under Creative Commons Attribution 4.0 (CC BY 4.0). You may share and adapt the data, including commercially, provided you credit Kalkylkartan, link to this page and the licence, and indicate changes. The licence cannot be revoked for uses that comply with its terms.
This licence covers only these test result data, not the website's code, logo, other editorial text, map tiles or third-party source data. Those retain their own terms. The shared CSV retains its original Swedish labels.