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

Taiwan Province Third-order Control Points Reconstruction and Implementation

(Years:1995~2003,2016~2017)

• Initiation: The original control points network in Taiwan were established during Japanese Occupation Period, and they suffered severe damages or missing due to natural disasters and variations of landform and ground features. Practically, some points have been sporadically re-established basing on the temporary needs of projects by various units. They lack overall planning and have led to inconsistent precision. The NLSC developed a project for comprehensive re-establishment and new establishment of the third order control points in Taiwan for the purpose of integrating all existing results.
• Area: The island of Taiwan, Penghu County, Kinmen County and Lienchiang County of Fujian Province.
• Achievement: A total of 4,710 points have been re-established or newly established based on GPS satellite positioning survey, and the “Control Point Database Management System” has been established manage surveying results for the purpose of inquiry and accordance with by surveyors of all fields.

Taiwan and Fukien Area Third-order Control Points Management and Maintenance

(Years:2004~2007)

• Initiation: The third order control points checking surveying operation have been implemented in coordination with that operation of the first order and the second order satellite control points, benchmarks, and gravity points checking surveying performed by the Ministry of the Interior.
• Area: The west plain of Taiwan is the prioritized choice, followed by Kaohsiung/Pingtung, Lanyang Plain and East Rift Valley in eastern Taiwan, and outlying islands. Among them, Penghu County, Kinmen County and Lienchiang County of Fujian Province of the outlying islands are areas with less obvious crustal deformation such that they are not included.
• Achievement: The third order control points management and maintenance of all 22 counties and cities in the island of Taiwan have been completed with a total of 6,146 points checked up, 543 points re-established, and 5,083 points resurveyed.

Velocity Field Management and Maintenance of National Basic Control Point

(Years:2008~2010)

• Initiation: The impacts of tectonic movements have resulted in severe displacement on control points and distortion of coordination system. Therefore, velocity field models of individual level of control points should be established to analyze how the severe impacts of crustal deformation on coordinate system. This center has adopted the e-GPS real-time kinematic positioning technology since 2008 to handle the velocity field of the third order control points. The detailed regional velocity field database in Taiwan has been established basing on the relevant observation data of three consecutive years.
• In principle, every point in this operation should be observed twice per year. The velocity field deformation diagrams of the Taiwan Island along the horizontal and vertical directions are shown in the figures below. The gradient diagram is composed based on the velocity field data of all the third control points interpolated into a 10”×10”(second) grid. The magnitude and the direction of arrow indicate the average velocity field of each township.

  

  Velocity field deformation diagram of Taiwan
  along horizontal direction Velocity field deformation diagram of Taiwan
  along vertical direction

   

  Year	Period	Processed quantity (Points)
  2008	1	4,234
  2008	2	4,064
  2008	3	1,639
  2009	1	4,028
  2009	2	4,208
  2010	1	2,657
  2010	2	3,984

Basic Control Point Measurement and Management

(Years:2010~2020)

Year	Content of operation	Scope of operation	Processed quantity (Points)
2010	Re-establishment and resurveying in Typhoon Morakot disaster area	Nantou County, Chiayi County (City), Tainan City, Kaohsiung City, Pingtung County, Taitung County and their outlying areas	●1,954 points checked up ●135 points re-established ●1,681 points resurveyed
2011	Detection of basic control points in northern Taiwan	Taipei City, New Taipei City, Taoyuan County, Hsinchu County (City), Miaoli County, Taichung City, Changhua County, Yunlin County, Nantou County, Keelung City, Yilan County, Hualien County, and their outlying areas	●1,225 points cleaned up ●1,098 points detected
2012	First order benchmark e-GPS measurement	All counties and cities of the Taiwan Island	●2,083 points cleaned up ●1,991points measured
2012	The detection of basic control points with TWD97【2010】	All counties and cities of the Taiwan Island	●1,460 points are cleaned up ●1,375 points are detected
2013	The detection of basic control points with TWD97【2010】	All counties and cities of the Taiwan Island	●1,426 points are cleaned up ●1,396 points are detected
2016	The detection of basic control points with TWD97【2010】	All counties and cities of the Taiwan Island	●1,483 points are cleaned up ●1,410 points are detected
2017	The detection of basic control points with TWD97【2010】	All counties and cities of the Taiwan Island	●1,463 points are cleaned up ●1,421 points are detected
2020	The detection of basic control points with TWD97【2020】	All counties and cities of the Taiwan Island	●2,718 points are cleaned up ●2,354 points are detected