Compass B2a与GPSL5信号间干扰仿真分析

首先介绍了卫星导航系统间干扰评估方法,仿真计算了CompassB2a与GPSL5信号间的相互干扰。干扰分析结果表明：Compass B2和GPSL5信号之间可以实现兼容,为进一步开展B2与L5信号间的互操作研究打下了基础。     

一种用于BDS-3接收机工程实现的两级B1C信号捕获技术

北斗三号卫星导航系统(BDS-3)B1C信号相较北斗二号卫星导航系统卫星信号,从信号结构、编码方式再到导航电文结构都发生了改变,包括引入导频信号、二次编码、BOC调制、LDPC编码和B-CNAV1导航电文结构等.这些改变一方面提高了信号性能(如抗多路径、信号捕获和跟踪精度等);另一方面,也带来了一系列问题,对接收机的信号捕获技术提出了全新的要求,如需处理更大的数据流,解决由二次编码带来的符号翻转和BOC调制造成的捕获多峰性问题.针对BDS-3接收机的工程实现,本文提出了一种新颖有效的两级B1C信号捕获技术.其中第一阶段采用扩展并行平均相关搜获结构,用以解决符号翻转问题,同时实现高效的信号粗捕获;第二阶段在缩小的搜索范围内进行高精度搜索,此步骤可有效避免信号多峰性造成的误锁可能.除此之外,本文还介绍了单信道和多信道组合式捕获技术,用户可根据资源占用和捕获灵敏度需求选取更有效的捕获方法.实验结果表明,本文提出的方法允许使用更小更经济的快速傅里叶变换(FFT)模块,并通过大量并行处理的方法实现快速捕获.相较传统的高精度捕获技术,此方法在采样频率超过50MHz时,能够在保证相近的捕获精度的同时减少至少61%的运算量.     

BS-ACEBOC: a generalized low-complexity dual-frequency constant-envelope multiplexing modulation for GNSS

GPS Solutions - In order to satisfy the need for combining signals in a constant-envelope modulation, we propose a new dual-frequency constant-envelope modulation (DCEM), called asymmetric...     

北斗B1C、B2a信号非理想性分析及接收约束建议

卫星导航信号的非理想性会导致不同接收机之间出现测距偏差,是影响卫星导航系统服务精度和完好性的重要因素。首先,针对北斗系统B1C、B2a新体制信号的非理想性进行分析,利用大口径天线采集了全部北斗三号在轨卫星播发的B1C、B2a信号（共27颗卫星）,评估了不同接收带宽、码鉴相间距下测距偏差的大小与变化特点;然后,以双频多星座星基增强服务应用为例,分析了两个信号在相应接收机中的设计约束条件。研究结果发现,在接收机常用的参数范围内,B1C、B2a信号非理想性引入的测距偏差分别不超过0.68 m、0.44 m;在测距偏差小于0.1 m的性能约束下,B1C、B2a信号可用的约束条件参数范围优于国际民航标准草案中的相关要求。     

遥感技术在考古中的应用综述

遥感技术能够快速有效地探明地上和地下古遗址的分布信息,在现代考古中发挥着重要的作用,逐渐成为考古研究的重要手段。阐述了遥感考古探测的基本原理,以遥感考古探测平台为序系统介绍了遥感考古探测方法与进展情况,对遥感考古探测的作用、局限性及发展前景进行了评述。     

Water body mapping method with HJ-1A/B satellite imagery

This paper proposes an integrated water body mapping method with HJ-1A/B satellite imagery, the CCD (charge coupled device) data of the Chinese environmental satellites that were launched on September 6th, 2008. It combines the difference between NDVI and NDWI (NDVI–NDWI) with SLOPE and near-infrared (NIR) band. The NDVI–NDWI index is used to enhance the contrast between water bodies and the surrounding surface features; the topographic SLOPE is used to eliminate the mountain shadow; and the NIR band is used to reduce the effects of artificial construction land. The objectives are evaluating the potential of the HJ-1A/B imagery on water body monitoring, and proposing ideally mapping method. The test study results indicated that the NDVI–NDWI index is superior to the single index of NDVI and NDWI to enhance the contrast between water bodies and the rest of the features. On the basis of the accurately mapped water bodies in the HJ-1A/B CCD images of the study area, we conclude that the HJ-1A/B multi-spectral satellite images is an ideal data source for high spatial and temporal resolution water bodies monitoring. And the integrated water body mapping method is suitable for the applications of HJ-1A/B multi-spectral satellite images in this field.     

BDS-3新频点B1C/B2a动态数据特性及PPP精度分析

通过载噪比(CNR)、数据完整率、伪距与载波相位观测值噪声和伪距多路径效应四个指标对北斗三号卫星导航系统(BDS-3)新频点B1C/B2a车载动态数据的特性进行了分析,测试了BDS-3新频点动态精密单点定位(PPP)的性能,并与其它全球卫星导航系统(GNSS)进行了对比.试验结果表明,BDS-3新频点B2a平均CNR优于北斗卫星导航系统(BDS)其它频率,但略差于GPS L5;相较于其它GNSS,BDS数据完整率相对较高,其中BDS-3 B2a新频点数据完整率最高;BDS-3 B2b伪距观测值噪声最小,B1C和B2a伪距观测值噪声约为B2b信号的3倍,但不同频率相位观测值噪声处于同一量级;对于伪距多路径而言,BDS-3 B1C/B2a信号略小于B2b信号.总体而言,GPS L5信号抑制多路径效应的能力最强.在动态PPP性能方面,BDS-3 B1C/B2a双频组合动态PPP定位精度最优,其三维(3D)均方根(RMS)误差为0.439 m,相比BDS B1I/B3I、GPS L1/L2、 GLONASS G1/G2和Galileo E1/E5a双频组合PPP,其精度改善率分别为49%、 5...     

省级基础测绘1:10000 DLG生产工艺的优化

本文通过省级基础测绘DLG更新生产方法的研究,寻求一种高效率、高质量的生产流程,满足本轮基础测绘更新的要求。     

The negative alpha filter: a new Processing technique for polarimetric SAR interferometry

In this letter we develop a new concept, the negative alpha filter, which we suggest has application for quantitative estimation of surface parameters beneath vegetation using polarimetric synthetic aperture radar (SAR) interferometry (POLInSAR). We first derive the filter and then validate it using simulations of L-band coherent forest scattering. We then show initial results of applying the filter to airborne data from the German Aerospace Center's E-SAR L-band sensor.     

POS技术在平原地区1:10000 DLG生产中的外业控制点布设

POS(DGPS/IMU)技术能够获取航摄瞬间航片外方位元素,采用POS技术进行空三加密和DLG制作,能够节省大量的外业控制点,这对提高航测地形图生产效率,降低成本具有重要意义。本文主要研究POS技术在平原地区1:10 000地形图生产中的外业控制点布设。设计了二十三种外业控制点布设方案,采用集成传感器定向法进行空三加密试验,在实验结果的基础上选择精度符合要求的数据制作了一幅1:10 000DLG,并对其进行精度测试。通过试验和研究,提出了合适的外业控制点布设方案,为POS技术应用于大规模航测4D产品生产做好技术准备。     

Estimation of forest aboveground biomass from HJ1B imagery using a canopy reflectance model and a forest growth model

Accurately estimating the spatial distribution of forest aboveground biomass (AGB) is important because of its carbon budget forms part of the global carbon cycle. This paper presented three methods for obtaining forest AGB based on a forest growth model, a Multiple-Forward-Mode (MFM) method and a stochastic gradient boosting (SGB) model. A Li-Strahler geometric-optical canopy reflectance model (GOMS) with the ZELIG forest growth model was run using HJ1B imagery to derive forest AGB. GOMS-ZELIG simulated data were used to train the SGB model and AGB estimation. The GOMS-ZELIG AGB estimation was evaluated for 24 field-measured data and compared against the GOMS-SGB model and GOMS-MFM biomass predictions from multispectral HJ1B data. The results show that the estimation accuracy of the GOMS-MFM model is slightly higher than that of the GOMS-SGB model. The GOMS-ZELIG and GOMS-MFM models are considerably more accurate at estimating forest AGB in arid and semiarid regions.     

利用1:2万既有航片测绘1:2 000地形图的探讨

对利用1∶20000左右既有航摄资料采用全数字摄影测量系统测制1∶2000城郊规划用图进行探讨。作业中采用了相应的技术加强措施。测图工作结束后,又在测区进行了模拟导线和散点两种方法对图纸进行了高程、平面、精度的抽查,其结果表明,测图精度达到了预期值,满足了规划用图的需要。该方法可为今后一些局部地区急需用图,测绘作为借鉴。     

HJ-1A/B卫星CCD影像辅助的MODIS水色大气校正产品质量改进

针对我国近岸高浑浊水体区域MODIS短波红外波段大气校正产品中存在的信号饱和及条带问题,利用神经网络模型,采用准同步的HJ-1A/B卫星CCD影像及实测遥感反射率数据对MODIS/Terra水色遥感大气校正产品进行了质量改进。改进后结果与MODIS/Terra遥感反射率产品相比,平均相对误差为13.3%,信号饱和区域修复结果与实测数据各波段平均相对误差为28.2%。结果表明,该方法在保证结果精度的情况下,能有效地修复MODIS/Terra水色波段因为信号饱和而产生的数据空白区域,同时也能较好地解决MODIS/Terra大气校正产品中的条带问题。     

Bonemapping: a LiDAR processing and visualization technique in support of archaeology under the canopy

For the past decade, archaeologists have been using LiDAR or Airborne Laser Scanning (ALS)-based methods to uncover trace signatures of human civilization in the landscape. A new technique called bonemapping involves processing the ALS data to create a map-like representation of the landscape, which aids in the detection and interpretation of traces of human settlement. The technique is a combination of two methods – the Simple Morphological Filter (SMRF) for ALS processing and the Perceptually Shaded Slope Map (PSSM) for ALS representation – and is used to represent subtle changes in the terrain that are often indicative of previous human settlement. The SMRF algorithm adds value by retaining more “feature” cells than comparable terrain-finding algorithms, and is easy to tune through the use of two intuitive parameters – a slope threshold and a window size. The PSSM visualization is then used to apply a vertical exaggeration-based slope shading, which has proven useful as an aid to rapid feature detection, identification, and interpretation. The findings of two years of field use of bonemapping by archaeologists at El Pilar demonstrate the ways in which the bonemap offers a value-added perspective to archaeology under the canopy.     

一种监测东营油田地表形变的方法

针对传统永久散射方法和相干目标法干涉图相位解缠的不足,该文提出了一种改进的多主影像相干目标小基线干涉方法。采用融合永久散射方法和相干目标法的优点,较好地平衡了失相干因素的去相干性与干涉目标点之间的矛盾,利用较小的数据集实现地表形变反演;基于14景COSMO-SKYMED雷达影像,采用多主影像相干目标小基线干涉方法提取地表形变信息。基于水准数据验证后的实验结果表明:所提方法不仅可以准确快速地监测出地表沉降区,而且监测精度较高,研究结果可以应用于城市形变监测、地震、滑坡等领域。     

全国1：1万主比例尺土地利用元数据库系统建设现状及应用

本文介绍了全国1:1万主比例尺土地利用元数据库系统建设的意义、设计思想、数据库结构、内容以及系统功能,概括了元数据库建设现状和应用范围,提出了有待解决的问题和建议。     

利用1:2000数字地形图编制1:10000建库数据的实践与探索

目前,我国很多城市拥有适时更新的大比例尺数字地形图,如何利用已有资源快捷地编制中小比例尺的建库数据,值得研究和探讨.文中给出在MicroStation中利用1:2 000数字地形图编制1:10 000建库数据的方法与技术.使用数字高程模型编制等高线并结合地形和高程模型进行等高线的编辑、裁剪,采取从数字地形图上直接拾取和外业调查相结合的方式获取地形要素的属性值,有效解决编制地理信息系统建库数据的实际问题.     

江苏省1:25万、1:100万基础数据修测与建库

1:25万、1:100万基础数据是江苏省地理空间信息基础框架的重要组成部分,本文根据江苏省地理空间信息基础框架的要求,结合全省现有的基础地理数据库建设的现状,叙述了对全省范围内的17幅1:25万DLG、DOM,4幅1:100万DLG数据如何进行修测、更新和入库,并建立相应的元数据库的过程和方法.