This Application Programming Interface (API) provides instant conversion between HK 1980 Grid Coordinates (Northing and Easting) and WGS84 (ITRF96) Geodetic Coordinates (Latitude and Longitude). The conversion methods, parameters and formulas used in the coordinate conversion tool provided in this API are maintained by the Survey and Mapping Office, Lands Department. It is only applicable for coordinates within Hong Kong.
Users SHOULD NOT use the results for applications requiring precise point positions. Transformation between datums does not improve the accuracy. In most cases, the transformation coordinates would be less accurate, because of the errors in the transformation and projection computation would be added to the results. Please seek advice from professional land surveyors. For enquiry, please contact the Geodetic Survey Section, Survey and Mapping Office, Lands Department.
For details, please refer to User Manual (English Only): http://www.geodetic.gov.hk/transform/tformAPI_manual.pdf