Design Of Static Measurement GPS Receiver Based On ARM

Global Position System(GPS) is build upon the rapid development of modern science and technology.To receive navigation satellite signal based on the autonomous navigation and positioning system,the system is just use for military at first,after open up for civilian use it is quickly permeated to all walks of life.The use since it was introduced in China in the 1980s indicated that the GPS positioning technology bring a profound technical revolution in the domain of surveying and mapping with the advantage of dispense with visual between observatories,less input in measuring groups and so on.The GPS technology is an important field in the application of geophysical exploration.The fieldwork of geophysical exploration need to measure the point position and elevation while make geophysical filed survey,the GPS technology have the advantage of high accuracy and high efficiency,and more convenient in contrast with traditional geodesic ways.Commonly, the accuracy of level elevation is about one meter,but gravity prospecting requires the accuracy of elevation positioning to centimeters.The accuracy can not meet the requirement to pocket GPS,whose single machine positioning accuracy is only 3 to 5 meters,and we need use the dual-frequency differential GPS technology in geodesic work of gravity prospecting,the experiment is expensive.There have not a low-cost GPS receiver product for geophysics work in the market.The professional-grade difference GPS receiver's survey baseline length request dozens of kilometers generally,but the engineering geophysics investigation and other applies often do not need to achieve such a large measuring range.The thesis takes the design of a low-cost,using in the short-baseline and high precision difference GPS receiver as a goal.Considering the efficiency of the field work,the thesis proposes that the baseline length in the measurement is no more than 3km and observation time is no more than 10 minutes,taking the ARM microprocessor as the central controller,and using the fast static difference technology,to obtain the centimeter level of the plane positioning and elevation standard precisions. It has important practical significance to combine the ARM embedded technology and GPS technology,take full advantage of the characteristic such as low consume,small capacity,more function of ARM microprocessor,make use of ARM microprocessor with suitably GPS-OEM module,develop the GPS receiver which is suitable for the demands of geophysical professional.First,this article advanced the whole design scheme of static state difference measurement GPS receive,and then make emphases on the design method of the system,the design of the system divided into the hardware and software.The hardware part has mostly done the circuit design of the main control unit module LPC2214,the power circuit,the reset circuit,the clock circuit,the JTAG circuit,the system memorize expander,RS232 serial interface circuit,128*64 graphics dot matrix LCD circuit,I~2C and keyboard circuit,SD card storage interface circuit and GPS receive module interface circuit and so on.The software part is main completed the development of the system control programming,mainly contains several component such as the SD card software design,establishment of FAT16 file system,LCD Display,I~2C keyboard,GPS data transition and storage and so on.At last,system test is made to the GPS receiver,test plan is given and the result of the test is calculated and analyzed.Because only collected a known baseline data at present,the enough different length's known baseline has not come to the Positioning Accuracy of the prototype to analyze the rule along with the baseline length change.Therefore the designed experiment tests are given as follows.First,the repeated measure on the known baseline is used to understand the measuring accuracy of the prototype,and to determine the scope of measurement error.Secondly, the repeated measurements on the different baseline lengths,is used to understand the system random error's change tendency along with baseline lengths increase.Then,the repeated measures on ultra-short distances,comparing the results of measurement with ruler baseline data, is used to understand the range of measurement error in the ultra-short distances of the prototype and to make up for the lack of the baseline data.The experimental results indicated:the work of the receiver is stable.The pointing accuracy does not have the system error basically.The position error increases along with the baseline length increases.When the base length is smaller than 5kin,10 minute static differences locate the even distance are smaller than 5cm with the elevation difference standard deviation,satisfy the design requirements of the thesis.Moreover,the experiments on the effects of weather conditions are analyzed.Through the system design and the research,I mainly obtain the following conclusion:(1)The choice attempt of the GPS-OEM is successful.The difference positioning accuracy of the single-frequency GPS-OEM board given in the datasheet is smaller than 0.5m,this board displays the pointing accuracy is far more ideal than its nominal value in the relatively short baseline difference measurements.This feature provided one kind of efficient path to reduce the cost for the GPS receiver design on the small scope,the high precision and differential measurement,achieves the idea of design high-precision GPS receiver with to the low-grade GPS-OEM board.(2)The design concept of the GPS receiver system is reasonable.Taking the central controller with ARM,ARM has displayed a advantage on formidable in the data processing function and rich resources in the chip,simplified system's peripheral circuit,reduced the system development cost and enhanced system's stability.And it can satisfy the special requirements in the power,the volume and so on as a field using portable equipment.(3) The accuracy of the GPS receiver system meets the design goals of this thesis.The differential measurement results of the prototype with antennas indicated:when the baseline lengths do not surpass 3km,the 10-minute rapid static differential measurements results of measuring point position and the elevation precision may achieve the centimeter level;Along with the increase of the baselines length,the spot position error which and the vertical error the receiver locates increases;The effects of climate fluctuations were limited.The system can satisfy the needs of measuring points work in the big scale's geophysical prospecting and the engineering survey.Finally,this thesis points out the major deficiencies and gives the reasonable proposals for the next step works.