【正文】 uhan University and Qing jiang Hydroelectric Develop ment Corp. Ltd. Jointly developed a realtime supervisory system suitable for the quality management needs of roller pact ion in filling engineering, i. e. realtime supervisory system of filling construction quality( GPS system for short afterwards) . The system has prehensive functions of realtime, high precision, continuity, automation etc. , so can be applied to realtime supervising construct ion quality of filling paction for dam, road, protection dike, airport etc. and bees an effective assistant of ensuring the construction quality for project . Combining with engineering needs and system characteristics, the position, key techniques and schemes of the system are discussed in this paper. The height accuracy of the system is analyzed and the preliminary application is introduced. 1 Composition and characteristics of GPS Realtime supervisory system 1. 1 Composition of the system Hardware unit of the system mainly includes 3 parts as follows: 1) Receiving system of GPS satellite signals。 3) Computer system. Fig. 1 Illustration of the system work structure According to the requirements of paction for filling and ram ming engineering and construction quality management to system, the system is posed of supervisory center, work relay station, locale subcontrol station,GPS reference station and mobile terminals ( including roller paction machines and quality supervisor work ing vehicle) , regarding the effect of wireless munication from topographic environment. Fig . 1 is the illustration of construction quality supervisory system for filling paction project . If the topographic environment is good and the distance between the filling construction onthespot and the system supervisory center is not long, the work relay station can be removed. 1. 1. 1 Supervisory center Supervisory center is the heart of the system,where the differential data of GPS reference station are emitted to the GPS mobile stations, and at the same time, receiv es the position information fed back by the mobile stations continuously and real timely through wireless data munication. Combining the needs of construction,electronic display screen equipped in the supervisory center can realtimely display the accurate moving location and status information of the roller paction machin es as well as the quality supervisor working vehicle for paction planes of the dam, remotely monitor the state of paction quality of filling engineering, and offer leaders the basis of decision. T he processing , analysis, storage of the system data and so on are carried out in the supervisory center. 1. 1. 2 Locale subsupervisory station Locale subsupervisory station is the extension of the system control center, and provides convenience for locale supervisor. By accessing information of the system supervisory center, the supervisor can master the status of engineering construction and the construction quality in time just in the construction locale supervisor quality deviation appears, the supervisor can tackle with the construction side on the construction locale, reminding the constructors and asking them for rectifying. 1. 1. 3 GPS reference station GPS reference station is set for increasing the supervisory precision of the system by means of DGPS technology. We set a GPS receiver on a known site as a reference station and carry out GPS observation, then emit the GPS observation data and known location information of the reference station realtimely to the GPS mobile stations, and process the data along with mobile stations39。( 1 2) cm, which fully meets supervisory quality needs of horizontal position of the paction construction, and can efficiently supervise the movement track, velocity and rolled times of the roller paction machines. In regard to elevation, as long as the mobile terminals operate in a given way and rational elevation fitting model is adopted, the precision of the system also achieves 177。 ( 12) cm, which fully meets the control needs of thick ness and roughness of filling layers. 3) Stability of the system. Because the filling construction of modern face rock fill dam lasts allweathered 24hours without break, and many roller paction machines work simultaneously, it is required that the supervisory center,work relay station and each mobile terminal of the system work stably for a long time. Because of the fixed set of supervisory center and work relay station, if there is surely provision of work power, and without manual destruction and incorrect manipulation, there is no problem for running on normal condition. But the mobile terminal set in the roller paction machine not only suffers from the vibration effect of roller,but also is incorrectly manipulated easily when the driver suffers from work tiredness, therefore, the stability design of integrated system unit of mobile terminal bees a key problem. 4) Powersupply way. Because the reference station is set in the supervisory center, powersupply of its GPS host, radio of emission and reception, and superviso ry puter has no problem. As involving each mobile terminal, it refers to the powersupply problems of GPS host , radio of emission and reception, plat form puter and fan for heat emission etc. Experiment work takes outset accumulator jars to provide power,which can ensure work in a short time, but can not be used in a long time work of project , so there is need to use the roller paction machine to supply power in the formal operation of system. The problem key of powersupply is practicality and to ensure that it doesn39。1. 37 cm, 177。1. 30 cm respectively. The increase of searching circle radius improves the height accuracy of system, but not obviously . It is known as the height accuracy of the sys