double-theodolite observation [测] 双经纬仪观测

double difference phase observation 双差相位观测

Double Station Observation 双站观测

double-frequency observation 双频观测

double frequency observation 双频观测

double difference observation 双差观测值

Double Satellites Observation 双星观测

double-direction observation method 对向观测法

double-difference combined observation 双差组合观测值