【文章內(nèi)容簡介】 and convenient, which contains only several simple necessary steps such as turning on and off the unit , the equipment s of mobile terminal are pact , of small weight and size and its loading and unloading is also very easy. 4) High precision. Thank to GPS RTK technology adopted for data processing of the system and the distance between the mobile terminals of Shuibuy a project and GPS reference station does not exceed 3 km, it s horizontal precision achieves 177。( 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( read the analysis afterwards) , which can meet the control needs of thickness and roughness of filling layers of the paction construction. 5) All weathered 24hours work of many mobile terminals. In the case of using 10 mobile terminals simultaneously, the system has a munication rate no less than 100 Kbps, and can support the application of pointtopoint, pointtomultipoint and work relay station. The system does not suffer from the effect of weather , and meets the need of allweathered 24hours work of dam project . 2 Key problem and solution of the system design 1) RealTime supervision of rolled parameters. Parameters of the roller paction mainly refers to movement track, velocity, rolled times of the roller paction machines for mobile terminals, which need real time supervision, and can be used to control construction quality. Therefore, in order to ensure the realtime feedback of positioning data, the wireless munication data links need to achieve the function of pointtomultipoint and bidirectional high munication rate. The optimal design for solving the problem is to choose the mode of radio or GSM mobile phone. Taking account of the economy and practice ability, the system adopts wireless frequency augmented munication technology , achieves transmitting GPS differential data of the reference station realtimely to each mobile terminal, feeding back the three dimensional spatial location information of each mobile terminal realtimely to supervisory center and supporting position results at interval of one second. T his way,not only the system of each roller paction machine can reflect its own status o f on the display screen, but also the supervisory center and locale subsupervisory station can supervise the working status of each mobile terminal realtimely. 2) Precision of observation data. The precision of GPS RTK is cmlevel in general, considering that the distance between the mobile terminals of Shuibuya project and GPS reference station does not exceed 3 km, its horizontal positioning precision fully meets calculation precision needs of the movement track, velocity and rolled times of the roller paction machines. In order to ensure the elevation precision of thickness and roughness of filling layer, besides choosing high perform ance and antinoise dualfrequency GPS receivers, adopting proper method for acqui ring three elevations data of before filling, after filling and after paction and elev ation fitted model, can make the elevation accuracy increase. By analysis, the elevate ion precision can achieve177。 ( 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。t make destruction to the system equipment , in this way,exclusive power ponent and relevant cable conductor and adapter connector are designed and produced. 3 Elevation accuracy analysis of the system In order to evaluate the elevation accuracy of the system, on a filling surface of the experimental field, using a light car and taking the movement track covering the whole surface almost even, three groups of data of the same elevation surface are obtained. One group of movement track is illustrated as Fig . 2 ( the unit is meter) . As far as three groups of data collected in the experiment are concerned, because the velocity of the car are different and interval distance of two neighbored track line are unequal, the amounts of dots of th