Measuring coordinates Small errors in the initial length measurement, would scale the whole network Because of the earth is " nearly flat, measuring angles in horizontal plane only aoWs“ horizonta| coordinates”tobe determined Another technique is needed for heights 02/11/02 12.540Lec02
02/11/02 12.540 Lec 02 6 Measuring coordinates • Small errors in the initial length measurement, would scale the whole network • Because of the Earth is “nearly” flat, measuring angles in horizontal plane only allows “horizontal coordinates” to be determined. • Another technique is needed for heights
Measuring coordinates In 1950s electronic distance measurement(EDM)became available (out growth of radar Used light travel times to measure distance(strictly, travel times of modulation on either radio, light or near- infrared signals) 02/11/02 12.540Lec02
02/11/02 12.540 Lec 02 7 Measuring coordinates • In 1950s, electronic distance measurement (EDM) became available (out growth of radar) • Used light travel times to measure distance (strictly, travel times of modulation on either radio, light or nearinfrared signals)