A $42 MILLION cash injection has been approved for the Marine Department to set up a state-of-the-art office to digitally chart the territory's waters and improve safety conditions. The Hydrographic Office, which should be fully operational by mid-1995, is to take over the work of the British Admiralty, which for decades has produced the 14 maps of Hong Kong's waters and three around Macau. ''With so many changes constantly being made to Hong Kong's waters, most of the Admiralty's charts are out of date before they are even released,'' said Nick Emerson, head of the new office. ''I'm not knocking the Admiralty, because they are the world's top producer of hydrographic charts. But the fact is unless you are constantly out there charting you won't be able to keep up to date and will be creating real dangers for navigators.'' Artificial changes like dredging and reclamation work are not the only factors making navigation difficult for mariners and causing charting headaches for hydrographers. Natural changes to the seabed or coastline in areas that have not been mapped for decades are also creating risks, especially for large vessels with the potential to run aground. Admiralty hydrographers have not been here to do a physical survey since late 1972, and have for two decades been relying on the Marine Department and other government departments to provide updates on things like coastline changes, changes to water currents, new buoys and lighthouses. While maps for the busy Victoria Harbour are updated regularly, some maps like for the Mirs Bay area are almost a century out of date. Substandard methods used to chart the areas at the turn of the century leave worrying questions of accuracy. The new office aims to correct that with the most advanced charting technology available, that its backers say will result in the waters around Hong Kong being the most accurately charted in the world. The office, which currently involves some 15 staff, is to be upgraded to more than 100 next year. Most will be transferred from other Marine Department divisions, with two or three sent each year to Britain to get post-graduate degrees in hydrography. Two specially designed boats are being purchased that will eventually be on the waters almost full-time providing constant updates. Contracts for the two boats and charting equipment are currently being tendered, with the hope that the first maps will be ready by 1996. The new technology includes sonar, satellite receiving equipment that will enable it to tap into the Global Positioning System, and land-based positioning systems that generate accuracy to less than one metre. Sin Tak-cheung, a Senior Marine Officer who has been studying the set-up of a Hydrographic Office for almost a decade, said the $42 million cost was justified because top quality equipment was needed. Mr Emerson said the territory had ''simply been lucky'' avoiding accidents as a result of out-of-date or inaccurate charts. ''I honestly believe that Hong Kong is so dangerous that it is actually safe,'' he said. ''The mariners have become so knowledgeable in certain areas that they all know what to avoid and when to avoid using the maps that have wrong information on them. ''But that certainly doesn't make things okay.''