National Land Surveying and Mapping Center. Republic of China(Taiwan)National Land Surveying and Mapping Center. Republic of China(Taiwan)

Taiwan Gravity Survey

• Department of Land Administration of Ministry of the Interior and NLSC have been establishing gravity base stations and gravity control network starting from 2003 while implementing shipborne, airborne, and altimetry satellite gravity survey to improve the gravity data of the island of Taiwan and surrounding waters for the application by all fields.

Gravity Datum Station and Taiwan Gravity System

• National Gravity Datum Station
  • The “National Gravity Datum Station” was established in Hsinchu and was officially inaugurated in 2006. This station is equipped with absolute Gravimeter(FG-5), relative gravimeter(EG), superconducting gravimeter(SG) and the international standard grade “Laboratory of Geodesy and Geodynamics (LOGG)”. For the details of National Gravity Datum Station and Laboratory of Geodesy and Geodynamics (LOGG) please refer to the website http://www.logg.org.tw/.
• Taiwan Gravity Datum and System
  • The gravity datum includes Hsinchu Gravity Base Station (HS) and its dual absolute gravity points, one of which is the Hsinchu main point (point number: HS01) located within the station, and the other is Hsinchu secondary point (point number: HS02) located in the nearby of the National Measurement Laboratory.
  • Ministry of the Interior announced the results of gravity datum and system on December 25, 2009 and named it Gravity System 2009 (calledGS2009). The datum statistics are as shown below:

    Absolute gravity point	Gravity value at the point surface	Accuracy
    Hsinchu main point (HS01)	978901.91mgal	0.01mgal
    Hsinchu secondary point (HS02)	978913.96mgal	0.01mgal

Gravity Observation Data

• Announcement of Gravity Survey Results
  • The gravity survey results of Taiwan Gravity Network was announced by Ministry of the Interior on March 13, 2014 including 17 absolute gravity points, 683 first order gravity points, and 6,084 second order gravity points. Totally, 6,784 points were distributed over Taiwan, Penghu, Kinmen, and Matsu.
  • The gravity survey results of Taiwan First-order benchmarks in 2023 was announced by Ministry of the Interior on August 24, 2023 including 409 second order gravity points.
• Land Gravity Survey
  • The gravity survey data on the land territory had been established by relevant units since 1980, and a total of almost 4,000 pieces of gravity data had been accumulated by 2003 covering the scope from western plain to eastern narrow strip of land on the island of Taiwan.
  • In addition, Ministry of the Interior implemented “First and Second Order Gravity Survey” in 2004. In which, the high precision ground gravity values of a total of 4,500 points were measured.
  • NLSC conducted the gravity surveys of Hualien, Taitung, and mountain areas during 2011~2012 with respect to a total of 661 points covering Hualien, Taitung, and all mountain areas in Taiwan.
    

    Land gravity survey points
    distribution
    (Left) 1980~2003, (Right) 2004~2006

    

    Gravity points distributions in Hualien,
    Taitung, and mountain areas
    (Left) 2011, (Right) 2012

• Shipborne Gravity Survey
  NLSC conducted the shipborne gravity survey operations in sea areas of 50 km radius near Keelung, Liuqiu, Green Island, Lanyu, and Penghu during 2006~2008, and the shipborne gravity survey operations 20 km offshore surrounding the island of Taiwan during 2012 ~2013.
  

  ZLS DYNAMIC METERS

  

  The geometric relationship between the gravimeter
  placed in the cabin and the pier height

• Airborne Gravity Survey
  • Ministry of the Interior conducted the airborne gravity survey operation at the flight height of 16,000 feet in 2004 for quick obtainment of gravity survey results of mountain areas. It also conducted 5,000 feet low flight height airborne gravity survey operation in 2006 and 2008 respectively covering eastern sea and western sea of Taiwan and Dongsha Islands.
    

    The aircraft for airborne gravimeter operation

    

    Airborne gravimeter L&R Air-Sea Gravity System II