Research conclusions: From the theo retica l analysis, ad justment ca lculat ion w ith large amounts of the data of the ha lfface observat ion on CP III plane netwo rk and compar ison w ith a ll prec ise indexes of the ad justment calcu lation of the all- face observat ion data, itw as conc luded the half- face observationmode on CPIII plane netwo rk could subst itute forthe full- face observation mode. Th is research result could provide the basis for rev ision and improvement o f the "Eng ineering measurement specificat ion for h igh- speed ra ilw ay".