GPS技术在现代农业生产中的应用

GPS技术是通过接收卫星信号,从而实现地面或者空中移动物体的准确定位。目前各款GPS接收机中,在农业领域中应用比较普遍的是美国Trimble公司生产的AgGPS132接收机,该接收机功能最全面,有较好的性价比。该接收机是一个双通道、全数字、低噪声的接收机,共有12个卫星搜索通道,通过PortA和PortB输出RTCM、TSIP、NMEA格式数据和CAN信息。与GPS接收机相连接的农业设备通过处理该数据串,读出作业设备当前的位置信息,实现设备的准确定位作业。目前,实行信号差分是提高定位精度的方法之一,低成本的GPS定位设备由于没有差分功能,因此定…     

4种DGPS模块动态定位精度测试与分析

采用RTK-DGPS为参照,对GARMIN GPS15L、Ublox LEA-4S、Gstar GS-87和Gstar GS-89m-J共4种DGPS模块在单机模式、地面伪距差分模式和卫星差分模式下的动态定位精度进行了测试和分析.结果表明:(1)对于GARMIN GPS15L和Ublox LEA-4S,单机定位精度为米级,使用地面伪距差分定位可分别提高动态定位精度20%和87%;(2)总体上看,DGPS模块的地面伪距差分定位精度优于卫星差分定位,卫星差分定位精度优于单机定位;(3)在视野狭窄地段,无论单机定位、伪距差分定位还是卫星差分定位,动态定位精度都受到一定影响,和视野开阔地段相比,精度明显下降.     

GPS精密单点定位精度分析

GPS精密单点定位是利用IGS所提供的精密卫星星历以及钟差产品,通过单台双频GPS接收机的伪距以及载波相位观测值来进行精密绝对定位的方法。本文主要就GPS精密单点定位精度的相关问题进行详细的分析探究,以期能为该领域的学术发展起到促进作用。     

农业GPS定位中的多径抑制算法研究

[目的]随着我国现代化精细农业的快速发展,应用于农业的GPS定位精度要求日益提高,由于多径信号的不确定性,传统跟踪环路不能准确估计多径信号参数,也不能有效抑制多径干扰。[方法]因此,本文利用多径信号估计与消除技术抑制多径干扰,在跟踪环中引入自适应滤波器估计多径信号参数,准确计算码延迟和幅度衰减。[结果]构建多径信号抑制模块消除多径干扰,可获得直达信号的码延迟和载波相位。试验分析表明,本文提出的多径干扰抑制算法能够准确估计多径信号参数,有效抑制多径干扰。[结论]改进后的GPS接收机可以增强卫星定位精度,满足现代化农业提出的科学种田、精确管理的定位需求。     

农用机器人DGPS导航方法及数据采集

介绍了农用机器人DGPS的导航方法,以及利用VC++实现导航数据的采集的方法。实验结果证明农用机器人差分导航系统能大大提高GPS定位精度,达到农业生产的要求。     

GPS长基线测量卫星高度角对定位精度的影响

卫星高度截止角的选取对于GPS测量中的基线解算和平差都具有重要意义,它的取值直接影响了获取数据的卫星数目以及所获取数据的质量,对GPS测量的精度有着直接的影响。本文针对长基线GPS测量,研究卫星高度截止角对其定位精度的影响。结果表明,长基线GPS测量中卫星高度角的最佳值一般可设置为10°～15°,不宜太小。卫星高度角过低,虽然可以提高可观测的卫星数目,但是低高度角的卫星信号在传播过程中不仅多路径误差大,而且对流层折射偏差也大,同时容易产生多路径效应,造成观测数据质量的整体下降,进而影响定位精度。     

GPS定位试验及提高定位精度的方法研究

对3种不同的4个GPS接收机进行了定位试验,主要包括单点静态定位试验和动态测量面积的试验.经过一系列的数据分析和处理,分别得到了3种典型的GPS接收机在这2种试验条件下的定位精度及排序,并且采用算术平均值法对最佳测量次数进行了研究,提高了GPS单点静态定位的精度.提出了在数据处理中加入控制点的方法,提高了GPS动态测量面积的定位精度.     

单频GPS接收快速静态定位的应用

针对单频(GPS)接收机存在的问题,提出采用快速静态方法,在少于10km的静态相对定位中,观测时间由原来的1小时缩短到几分钟至十几分钟,其相对定位精度与静态定位精度相当.以某省二级公路GPS网为例,说明了单频GPS接收快速静态定位的应用.     

GPS在农业生产领域中的应用

GPS简介：GPS的全称是Global Positioning System(卫星导航定位系统)，是美国于1994年全面建成的全球定位系统。它由空间星座、地面监控和用户设备三大部分组成。在过地心的6个极地轨道面上，均匀分布着24颗GPS卫星，这些卫星全天候、实时地向地面发送卫星星历等定位信息，用户接收机根据接收到的卫星信息，实时计算所处的位置坐标，从而达到全球性、全天候、连续的精密三维导航与定位的目的。     

模拟退火遗传算法在手持GPS接收机中的应用

分析了手持GPS接收机在实际应用中定位精度的影响因素,提出了模拟退火遗传算法,并将该算法用于导航接收机中,建立了实现原理框图,进而提出了模拟退火遗传算法的具体步骤,通过实测检测得到较高的精度。     

基于GPS技术的定位测量精度试验研究

随着“3S”技术逐步在农业生产中的广泛应用,GPS技术在精细农业中的应用也越来越受重视。对测距码伪距GPS定位模型进行了推导和分析;利用AgGPS132接收机进行了单点定位和差分定位试验,对试验数据进行了分析与比较,试验结果表明差分定位精度要明显高于单点定位,定位精度能达到亚米级。     

Error Sources Affecting Variable Rate Application of Nitrogen Fertilizer

The accuracy and interaction among global positioning system (GPS) horizontal accuracy, differential GPS (DGPS) sampling frequencies and machine delay times of a hypothetical variable rate applicator for nitrogen (N) fertilizer application based on an application map in Florida citrus were studied. Parameters studied included: five GPS horizontal accuracy levels, two levels of DGPS horizontal accuracy, two DGPS sampling frequencies and two machine delay times. Two integrated models were developed which documented the effects of the parameters. Machine delay time was the most important factor and GPS horizontal accuracy was the second most important.     

Centimetre-precision guidance of moving implements in the open field: a simulation based on GPS measurements

High quality and sustainable agricultural production in the open field will be supported by centimetre-precision guidance of agricultural implements. In this paper, a complete guidance system is proposed and simulated using real sensor data obtained from a real time kinematic (RTK) differential global positioning system (DGPS). This type of the satellite navigation system became available commercially in 1997 and is claimed to reach cm accuracy. It uses real time kinematics to improve the accuracy of a position fix by phase comparison of the carrier signal. The simulation primarily aims to investigate the accuracy of the guidance system that can be obtained with RTK DGPS. Using real DGPS measurement errors the simulated system showed a tracking error less than 0.005 m when the PID-controller had settled.     

地图控件(MO)在农田信息系统开发中的应用

提出了地图控件MO(MapObjects)在农田信息系统开发中的应用方法，利用VC十十开发环境编程实现了农田信息系统的图层显示、属性查询、自动漫游及图形输出等功能，并且实现了AgGPS132接收机与台式机(PC机)之间的通讯。     

低成本农用GPS接收系统的研制及在面积测量中的应用

针对目前我国应用于精细农业的GPS接收系统成本高,不能接收虚拟参考站(VRS)差分信息的问题,采用低成本亚米级精度GPS接收模块,并结合ARM7微处理器、基于GPRS(general packet radio service)方式的无线通信模块、U盘存储模块、键盘和LCD设计研制了低成本GPS接收系统。该GPS接收系统可以通过GPRS方式接收北京VRS控制中心发送的差分改正信息,实现实时差分定位及长时间稳定的通信链路。定位信息通过串口输出(输出频率为1 Hz)和U盘存储2种方式实现数据的输出和保存,用户可利用本接收机进行定位和面积测量。面积测量实验结果表明,该接收机在不同大小、不同形状的面积测量中,其相对测量误差小于3%,满足精细农业中面积测量的要求。     

黑龙江精准农业示范区土壤养分空间变异研究

以面积为129 hm^2农田为采样区,使用Ag132 DGPS仪定位,网格法采集0～20 cm耕层土壤样品,实验室测定土壤碱解氮、速效磷、速效钾和有机质的含量.应用传统统计学方法和空间分析方法对土壤养分变异进行了研究.结果表明,土壤养分性质均存在着空间变异性,速效磷、速效钾和有机质变异相对较大,碱解氮变异亦小;土壤养分性质均存在半方差结构,分别拟合Exponential、Gaussian、Pentaspherical、Gaussian模型;碱解氮、速效磷、速效钾和有机质均显示中等的空间相关性.     

林冠与山地对GPS定位精度的影响及消减对策

为解决林冠与山地对RTDGPS定位精度影响的难题 ,作者在不同地类、不同地形、不同测程、不同林冠下进行RTDGPS复测实验 ,并获得数据 .通过数据统计分析 ,得出RTDGPS定位精度随上述因素变化的具体规律 .提出了应用高增益天线法、砍树剥枝法、升高天线高于树冠法、伪卫星法、GLONASS法、差分GPS +气压计法、延长观测时间法、插转台法等多种对策 ,在测区内高处设置插转台进行观测、选取适当的觇标高、选用适当的历元数等手段 ,通过增强GPS接收卫星的信号 ,提高定位精度 ,消减林冠、地形、测程等因素对RTDGPS定位效果的影响     

Implement lateral position accuracy under RTK-GPS tractor guidance

The accuracy of global positioning system receivers can be improved by differential correction systems (DGPS), which deliver sub-meter accuracy. Higher-accuracy, of about 1 cm on-the-go, is delivered by units generally referred to as real-time kinematic (RTK) DGPS systems. RTK-DGPS systems are presently used by commercial companies for automatic guidance of tractors in row-crop operations. Since high-end DGPS systems with high-accuracy are generally very expensive, it is necessary that the commercial benefit be maximized and that any related errors will be minimized. In the present study, the deviations from a predetermined route of a three-point hitch implement mounted on a RTK-DGPS based automatically guided tractor were recorded and were used to validate that the implement deviation is strongly dependent on the distance from the tractor rear axle. The recorded deviations were analyzed for paved and rough surfaces; the latter caused substantially greater deviations. Based on the above hypothesis, a possible way to improve the performance by reducing the deviations at a point on the implement is suggested.     

Assessing GNSS correction signals for assisted guidance systems in agricultural vehicles

Accuracy levels achieved with differential global positioning system (DGPS) receivers in agricultural operations depend upon the quality of the correction signal. This study has assessed differential signal error from a Dedicated Base Station, OmniSTAR VBS, European Geostationary Navigation Overlay System, European reference frame-IP for internet protocol (EUREF-IP) and radio navigation satellite aided technique (RASANT). These signals were utilized in guidance assisting systems for agricultural applications, such as tillage, harvesting, planting and spraying, in which GPS receivers were used under dynamic conditions. Simulations of agricultural operations on different days and at different time slots and simultaneously recording the tractor′s geo-position from a DGPS receiver and the tractor′s geo-position from a real-time kinematic (RTK) GPS allowed the comparison of the GPS correction signals. The hardware used for tractor guidance was a lightbar (Trimble model EZ-Guide Plus) system. ANOVA statistics showed a significant difference between the accuracy of the correction signals from different sources. GPS correction signal recommendations to farmers depend upon the accuracy required for the specific operation: (a) Yield monitoring and soil sampling (<1 m) are possible with all the GPS correction signals accessed in any time slot. (b) Broadcast seeding, fertilizer and herbicide application (<0.5 m) are possible for 80% of time with OmniSTAR VBS, 40% of time with RASANT and EUREF-IP and 100% of time with a dedicated base station. (c) Transplanting and drill seeding (<0.04 m) are not possible with the accuracy correction provided by any one of the systems used in this study.     

GPS快速静态定位技术在城镇地籍调查中的应用

[目的]为GPS快速定位技术在城镇地籍调查中的应用提供依据。[方法]山亭区城镇地籍调查控制测量项目采用D级GPS控制网作为测区首级控制网,利用4台Trimble 5700 GPS双频接收机进行快速静态测量,选用22个点构成骨架网,进行优化设计,利用TrimbleDINI12电子水准仪进行GPS四等水准联测。[结果]通过精度统计及分析,利用快速静态定位测量结合GPS水准成果,能满足C级以下GPS控制测量的要求,利用一定数量和分布均匀的GPS水准点进行高程拟合,能达到四等以下水准测量的精度。[结论]在城镇地籍调查中采用GPS快速定位技术建立首级控制网,取得了很好的经济效益。