地層下陷區水準網成果更新機制之研究

A study of updating mechanism for leveling network results at land subsidence area

內政部105年4月12日台內地字第1051302710號公告之「104年臺灣一等水準網水準測量成果說明」中，考量臺灣西部沿海地區受到地殼變動或人為因素造成沉陷情形嚴重，若採5年更新一次該區域一等水準點高程成果，期間內各點位實際沉陷量將遠超過檢測精度，公告成果受到持續沉陷影響，無法符合測繪業務所需之精度要求。經審慎評估後將彰化、雲林及嘉義等縣沿海地區劃分為地層下陷區水準網，區域內檢測點位不納入成果公告，該等點位測量成果得洽內政部國土測繪中心提供參考使用。為訂定地層下陷區水準網更新機制，期以較節省政府人力與經費，且成果精度符合基本測量實施規則中，以水準測量方法實施二等基本控制測量之精度規範±5.0mmF（F為水準環線長度之公里數）之原則，達到更新地層下陷區一等水準點正高之目的，本研究利用經濟部水利署、經濟部中央地質調查所及內政部國土測繪中心水準測量資料，並參考內政部國土測繪中心「101年度正高監測網聯測工作」作業方法與「103年度一等水準測量工作報告」建議之方法，就不同平差計算方式、約制點位及使用資料擬定4種方法，計算分析不同方法對地層下陷區水準網成果之影響，以評估建立地層下陷區水準網成果更新機制。研究結果顯示，不同方法對水準網成果之影響量均小於1公分，遠小於地層下陷區每年沉陷量3~8公分。因此依內政部國土測繪中心「101年度正高監測網聯測工作」作業方法，並將彰化、雲林及嘉義縣等3縣市水準測量資料由各縣市獨立平差調整為3縣市一併平差計算，作為後續地層下陷區水準網成果更新機制，可以較少的人力與經費，且不影響成果精度品質，達到更新一等水準點正高之目的。 The Ministry of the Interior, R.O.C announced “2015 Taiwan First Order Leveling Network Result” on April 12, 2016. Considering the crustal deformation and anthropic factor result in land subsidence, the precision of benchmarks in coastland of western Taiwan cannot afford the demand for surveying applications if update the orthometric height of benchmarks every 5 years. After serious and cautious consideration, the results of benchmarks nearby coastland in Changhua county, Yunlin county and Chiayi county were defined into “leveling network results at land subsidence area”, the checking results in that area were not announced. Users can acquire the results from the National Land Surveying and Mapping Center, Ministry of the Interior, R.O.C (NLSC). The leveling data from the Water Resources Agency, Ministry of Economic Affairs, R.O.C, the Central Geological Survey, Ministry of Economic Affairs, R.O.C, and the NLSC were utilized to set up updating mechanism for leveling network results at land subsidence area. It is expected to comply with the laws, retrench funds, and manpower. This study referred to the method of “2012 Orthometric height monitoring survey” and the suggestions raised in the study of “2014 First order Leveling work report”. 4 methods were used to analyze the effect on leveling network results by using different adjustment methods, constraint points, and utilized data. The results of the study showed that the effect on leveling network results by using different methods are smaller than 1 cm, the effect is smaller than the rate of subsidence 3~8cm per year. Therefore, it could achieve the objective to set up the updating mechanism for leveling network results at land subsidence area by according to the method of “2012 Orthometric height monitoring survey” and adjust the leveling network by combining the data from Changhua county, Yunlin county and Chiayi county.

The Ministry of the Interior, R.O.C announced “2015 Taiwan First Order Leveling Network Result” on April 12, 2016. Considering the crustal deformation and anthropic factor result in land subsidence, the precision of benchmarks in coastland of western Taiwan cannot afford the demand for surveying applications if update the orthometric height of benchmarks every 5 years. After serious and cautious consideration, the results of benchmarks nearby coastland in Changhua county, Yunlin county and Chiayi county were defined into “leveling network results at land subsidence area”, the checking results in that area were not announced. Users can acquire the results from the National Land Surveying and Mapping Center, Ministry of the Interior, R.O.C (NLSC). The leveling data from the Water Resources Agency, Ministry of Economic Affairs, R.O.C, the Central Geological Survey, Ministry of Economic Affairs, R.O.C, and the NLSC were utilized to set up updating mechanism for leveling network results at land subsidence area. It is expected to comply with the laws, retrench funds, and manpower. This study referred to the method of “2012 Orthometric height monitoring survey” and the suggestions raised in the study of “2014 First order Leveling work report”. 4 methods were used to analyze the effect on leveling network results by using different adjustment methods, constraint points, and utilized data. The results of the study showed that the effect on leveling network results by using different methods are smaller than 1 cm, the effect is smaller than the rate of subsidence 3~8cm per year. Therefore, it could achieve the objective to set up the updating mechanism for leveling network results at land subsidence area by according to the method of “2012 Orthometric height monitoring survey” and adjust the leveling network by combining the data from Changhua county, Yunlin county and Chiayi county.