水平角测量原理 The Meterage of horizontal Angle Principle J6型光学经纬仪 J6 Optics Theodolite 水平角测量 The Meterage of Horizontal Angle 竖直角测量 The Meterage of Erect Angle 经纬仪的检验与校正 The Inspection and Emendation of Theodolite 经纬仪测角注意事项 The Notice of Measured Angle by Theodolite