Class 1 Level Reference Net
To establish full height control net, the Ministry of Interior, during class 1 level reference net survey operation period, at the same time, carries out satellite positioning measurement and gravity measurement. Among them, the class 1 grade 1 level reference net survey is in accordance to the class 3 control point survey specifications. The class1 grade 2 level reference net survey is better than the class 3 control point survey specifications.
The above listed points will be used for grade 3 satellite control points. All results are configured on the 1997 Taiwan land base (TWD97). It uses 1994 published international terrestrial reference frame (ITRF94) and calculated to 1980 published reference ellipse body (GRS80), during survey, it cooperates the testing of class 1 and 2 satellite control points. It uses GPSurvey2.35 version software to calculate the base line, TurboNet net type horizontal difference etc. for weighted restriction horizontal difference calculation. The class 1 grade 1 level reference net horizontal results at latitude, longitude and height direction deviation average values are ±1.4 cm, ±1.3 cm, and ±10.9 cm, respectively. The class 1 grade 2 level reference net horizontal results at latitude, longitude and height direction deviation average values are ±1.6 cm, ±1.6 cm, and ±4.9 cm, respectively.

