How to use
In “Convert”, choose the type of coordinates you enter and try the example buttons. Latitude and longitude may be decimal (35.681236) or 35°40′52″ or 35 40 52.
You get decimal, DMS and degrees-minutes for the world datum (WGS84 / JGD2011), the Tokyo Datum values, plane rectangular coordinates for the zone you pick, UTM, Web Mercator, every level of mesh code and geohash. Each row has a copy button.
To turn plane rectangular coordinates into latitude and longitude, choose “Japan plane rectangular”, pick the zone (I–XIX) and enter X and Y. X is northing and Y is easting.
In “Batch”, open a CSV or Excel file, pick the latitude and longitude columns and the columns to add, then save the table as CSV or Excel. Rows that fail stay in the file with the reason.
In “Distance & azimuth”, enter two points to get the distance and azimuth on the GRS80 ellipsoid. You can also find a destination from a start point, an azimuth and a distance.
What it does
Tolerant latitude/longitude input
Reads decimal, DMS and degrees-minutes, N/S/E/W letters, Japanese 北緯/東経, full-width digits and the usual degree, minute and second marks. DMS output handles the 60-second carry correctly.
Plane rectangular coordinates from the GSI series formulas
Zones I–XIX are converted both ways with the Gauss–Krüger projection (GRS80, scale factor 0.9999). Automated tests check that each zone origin is (0, 0) and that the results agree with an independent series.
Tokyo Datum uses the simplified 3-parameter method
The conversion is a 3-parameter translation. The GSI TKY2JGD grid correction is not used, so errors of several metres remain. The page says so next to the results.
Mesh codes from 1st level to quarter mesh
Encodes the 1st–3rd, half and quarter regional meshes (JIS X 0410) and decodes a code back to its centre and cell size. Integer arithmetic keeps points on a cell boundary from slipping into the neighbour.
Batch conversion and geodesic distance
Convert up to 50,000 rows of a CSV or Excel file by column. Distance uses Vincenty’s iterative formulae on the ellipsoid, and the direct problem (destination from start, azimuth and distance) is included.
Use cases
- Turn decimal coordinates from GPS or a map app into DMS (or the other way round)
- Convert old Tokyo Datum coordinates in historical documents to the world datum
- Convert between plane rectangular coordinates used in CAD/GIS and latitude/longitude
- Add mesh codes or geohashes to the latitude/longitude columns of an address or store list
- Find the geodesic distance and bearing between two places
Capability matrix
| Feature | Support | Notes |
|---|---|---|
| Latitude/longitude notation (decimal, DMS, degrees-minutes) | Supported | — |
| World datum (WGS84, JGD2011, JGD2000) ⇔ Tokyo Datum | Partial | Simplified 3-parameter method; no TKY2JGD grid, errors of several metres |
| Plane rectangular zones I–XIX ⇔ latitude/longitude | Supported | World datum (GRS80). Tokyo Datum plane coordinates are not supported |
| UTM and Web Mercator (EPSG:3857) | Supported | The special UTM zones of Norway and Svalbard are not applied |
| Regional mesh codes (1st–3rd, half, quarter) and geohash | Supported | — |
| Batch conversion of CSV / Excel | Supported | Up to 50,000 rows and 20 MB |
| Distance and azimuth between two points (ellipsoidal) | Supported | Nearly antipodal points cannot be calculated |
| Use as survey results under the Japanese Survey Act, geoid height or elevation conversion | Not supported | For high-accuracy survey work use the GSI calculators or survey software |
| Showing a map | Not supported | No external maps are loaded; only links that open Google Maps or GSI Maps |
| Crustal deformation correction (JGD2000 vs JGD2011) | Not supported | They are treated as the same datum |
Limits & notes
- JGD2011, JGD2000 and WGS84 are treated as the same coordinates. Differences from crustal movement (tens of centimetres in Tohoku and elsewhere) are not corrected.
- The Tokyo Datum conversion is the simplified 3-parameter method with errors of several metres (up to about 10 m in some areas). Height is taken as 0 m.
- Plane rectangular coordinates are meant for the area assigned to each zone. A warning is shown far from the origin. Which zone applies is set by prefecture and municipality.
- Batch conversion handles up to 50,000 rows and 20 MB. Only the first sheet of an Excel file is read.
- Survey results under the Survey Act, geoid height, elevation conversion and map display are not supported.
Privacy & safety
The coordinates you type and the CSV or Excel files you open are converted in your browser only. Nothing is sent to or stored on a server. The Google Maps and GSI Maps links open a URL containing the coordinate only when you click them.
FAQ
How do I convert latitude and longitude to DMS?
What is the difference between the Tokyo Datum and the world geodetic system?
How do I choose the plane rectangular zone?
What is a mesh code?
Can I use the results for surveying?
Are my coordinates or CSV files uploaded?
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