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1.
星基差分GPS用于林区高分辨率遥感图像几何精校正 总被引：6，自引：0，他引：6
为解决林区缺乏大比例尺地形图而难以进行高空间分辨率遥感图像几何精校正问题,采用基于广域差分技术的星基差分GPS精确测定地面控制点(GCP),以多项式变换进行QuickBird pan(0.61 m)图像几何精校正.结果表明,全部GCP的点位误差均小于1个像元,总的点位误差为0.411 9.在进行图像灰度重采样中,最邻近点法、双线性内插法和三次褶积法的效果均无明显差异;就信息量和灰度值变动情况而言,以三次褶积法略好;就图像灰度保真而言,以最邻近点法略好. 相似文献
2.
基于科学调查与渔业生产数据的山东近海口虾蛄生长参数估算 总被引：2，自引：1，他引：1
渔业资源评估一般有两种数据来源,即科学调查数据和渔业生产数据;前者需要定期出海采样,耗时长且费用高,后者易于获取但样本代表性存在问题。本研究以山东近海口虾蛄为例,基于电子体长频率方法(ELEFAN)评估了口虾蛄的生长参数,采用bootstrap 重抽样方法比较了基于渔业生产数据与科学调查数据分析结果的差异,旨在探讨渔业生产数据在估算生长参数上的准确性。结果表明,科学调查数据估算得到的口虾蛄von Bertalanffy季节性生长方程中的极限体长L∞=193.16 mm, K=0.62,生产数据估算得到的口虾蛄极限体长L∞=171.70 mm,K=0.67;非参数检验表明基于两种采样方法所求得的口虾蛄的极限体长L∞呈现显著性差异, K 和“夏季点”ts 均呈现不显著性差异。本研究表明,渔业生产数据在一定程度上能够反映生物的生长状况,对K 和ts 的估算与科学调查数据估算的结果较为接近,但对极限体长的估算误差较大。因此口虾蛄生长研究需要依靠科学调查数据的支持,同时渔业生产数据可以作为辅助信息。 相似文献
3.
The successful development of phenology models from field studies depends on many factors, some of which are entirely under the control of pest managers. For example, one such factor is the choice of method for calculating thermal units. In this study, we have demonstrated that four methods for calculating thermal units provided for acceptable predictions of one phenological event of one insect species, while another method for calculating thermal units did not. The measure of central tendency (mean or median) that is used to estimate lower developmental temperatures and required thermal summations is another factor that pest managers can control when developing phenology models from field studies. Here, we show that predictions that were made when using phenology models based on median lower developmental temperatures and median required thermal summations were superior to predictions that were made when using phenology models based on mean lower developmental temperatures and mean required thermal summations. The use of bootstrap vs. non-bootstrap estimates of lower developmental temperatures and required thermal summations is yet another factor that pest managers can control when developing phenology models from field studies. In this study, we found that calculating and using bootstrap estimates of lower developmental temperatures and required thermal summations in phenology models did not improve the predictions of one phenological event for one insect species. The implications of these and other findings are discussed. 相似文献
4.
基于改进粒子滤波的农用车辆导航定位方法 总被引：5，自引：5，他引：0
针对农业机械导航系统中常用的Kalman滤波对多传感器数据进行融合的算法不适用于非线性农用车辆导航系统的问题,该文采用粒子滤波方法进行数据融合,以获得准确的导航定位信息;该算法增加抗野值步骤,有效削弱GPS跳变引起的误差;通过对重要密度函数进行改进,引入无迹卡尔曼滤波方法（UKF）,并采用不同重采样方法,有效抑制了粒子退化;增加MCMC步骤,减少了样本枯竭现象。仿真结果表明,改进后粒子滤波方法,可有效提高精度,减小导航误差,可满足农用车辆与作业机械的导航要求。 相似文献
5.
基于LAI时间序列重构数据的冬小麦物候监测 总被引：5，自引：2，他引：3
农作物物候信息对农作物长势监测和估产具有重要意义。该文以河北省中南部冬小麦为研究对象,以叶面积指数(LAI,leaf area index)为同化量,采用重采样粒子滤波算法同化WOFOST(world food studies)作物生长模型和遥感观测LAI,重构LAI时间序列数据,基于重构数据提取冬小麦返青期、抽穗期和成熟期等关键物候期。重构结果表明,重构的LAI具有良好的时间连续性和空间连续性,可减缓WOFOST作物模型LAI变化剧烈程度,峰值出现时间与遥感LAI曲线基本同步,且可一定程度上解决遥感观测LAI数值整体偏低和数据缺失的问题。物候期监测结果表明,在空间分布上与冬小麦实际生长状况基本相符,时间上也较为合理,但因在返青期存在LAI高初始值、成熟期存在LAI下限不确定性等问题致使在具体日期存在偏差。 相似文献
6.
为获得若尔盖地区较长时间序列的遥感植被指数,采用重采样技术和一元线性回归方法实现了GIMMS NDVI和MODIS NDVI的空间尺度转换和时间尺度外推。结果表明:（1）不同重采样方法对MODIS NDVI数据的影响与空间尺度有关,对GIMMS NDVI数据的影响则与空间尺度关系不大;（2）空间分辨率2.5 km,对不同植被类型可建立GIMMS NDVI和MODIS NDVI数据的一元线性转换关系,利用GIMMS NDVI拟合的结果与MODIS数据的差值统计符合正态分布;（3）1982—2013年,以1998年为节点若尔盖地区的植被先退化后逐渐恢复,尽管近几年植被指数平均水平高于研究初期,但局部地区的植被退化形势仍然比较严峻。 相似文献
7.
武功山山地草甸主要群落类型高光谱特征 总被引：2，自引：0，他引：2
本研究以江西省武功山金顶风景区的五节芒(Miscanthus floridulus)、野古草(Arundinella hirta)、飘拂草(Fimbristylis wukungshanensis)、中华苔草(Carex chinensis)、箭竹(Sinarundinaria nitida)为优势物种的5种主要群落为研究对象,以美国SVC HR-768野外便携式地物波谱仪测定的高光谱数据为基础,利用重采样、一阶微分和去包络线3种数据处理方法分别提取有效的光谱吸收特征参数,以此获得区分5种草地群落的光谱特征。结果表明,1)5种群落光谱反射率组间差异显著(P0.05),光谱反射率表现为中华苔草野古草五节芒箭竹飘拂草;2)重采样处理得到的特征参数中500-600、600-700和1 200-1 300nm 3个波段的波峰/谷深度差别都最明显,一阶微分处理提取的红边、黄边和蓝边有关的特征参数也能够很好的将5种群落进行分类,而利用连续统去除法提取的特征参数中,吸收谷的宽深比差值最大可达到92,是区分5种群落最有效的特征参数;3)波峰/波谷对应的波长位置是山地草甸5种主要群落的共性参数。 相似文献
8.
鱼类种群的体长分布能够反映该种群的资源变动状况,但能够有效描述体长结构信息的采样量难以确定。通过使用重采样方法计算了基于实际采样量下体长频次分布和基于模拟采样量下体长频次分布之间的均方差异值,并以温台渔场几种经济鱼类为例,比较了不同鱼种间体长频次精度和采样量间的关系,研究表明：(1)鱼种间的生物学差异、季节变化等因素对体长频次精度与采样量间关系有一定影响;(2)迭代计算中体长组数量的改变会影响体长频次精度估计的准确性;(3)为避免采样努力量的浪费,体长频次精度的大小可作为采样量优化的理论依据。由于目前国内缺乏估计体长频次精度一类的研究,本文的研究结果可对相关资源调查的设计提供一定的科学理论基础。 相似文献
9.
Tony Kess 《Scandinavian Journal of Forest Research》2014,29(7):707-712
Gene flow from outside pollen sources reduces the expected genetic gain of seed orchards, and has been quantified by genotyping seed samples from crop years to determine the proportion of seed sired by outside sources. Random bulk seed sampling and microsatellite genotyping allows for fast, unbiased identification of orchard contamination rates. Bulk seed sampling has been employed in multiple studies of seed orchard gene flow, but a method of determining precision of gene flow estimates from this sampling method has yet to be described. In this study, we used jackknife resampling to generate random samples of migrant and within-population genotypes obtained from an empirical sample of Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) genotypes of five microsatellite loci. We generated samples of 50, 100, 150, 200, and 250 genotyped individuals from a sample of 400 seeds, with genotypes corresponding to low (6%), moderate (14%), or high (56%) pollen contamination levels. The mean gene flow estimate and confidence interval were calculated for each sample size and gene flow scenario to determine the precision of gene flow estimates obtained from each sample size in each contaminant gene flow scenario. Genotyping 150 individuals was sufficient to produce gene flow estimates with calculated confidence interval values below ± 1%, indicating that 150 genotyped individuals were sufficient for precise gene flow estimation in this population. This resampling method will enable precise and unbiased estimation of gene flow into seed orchards for future monitoring of gene flow, to allow better management of seed orchard genetic resources. 相似文献
10.
Soil biodiversity varies through space as influenced by habitat features and land-use history. The performance of any sampling strategy highly depends on its relevance with regards to this pattern. We surveyed the soil macrofaunal species richness in the pastures of the Benfica Field Station (Eastern Amazonia, State of Pará, Brazil) and described its variability in 4 independent replicate plots. We designed a within-plot sampling scheme that accounted for the soil spatial variation (stratified sampling). Replicated pasture plots had different species richness (49-65) corresponding to a low proportion (40-53%) of the total number of species (123). Pairs of replicated plots showed an outstandingly low number of shared species (28-41% of the species pool). Likewise, different classes of soil thickness, corresponding to a Ferralsol-Cambisol sequence, had different species richness (12-44) and exhibited a very low proportion of shared species (15-29%). The proportion of rare species, i.e. singletons, ranged from 40-51% of the total species richness depending on the plot considered. We used the abundance-based coverage estimator of species richness (ACE) and the Chao shared species estimator that provides a correction based on the relative abundance of rare species. These indices also showed both a high between plots dissimilarity and a substantial within plot variability of species composition. Because of the high proportion of rare species, the rarefaction curves failed to reach any asymptote in all replicated plots. Bootstrap resampling showed that less than 5 samples per stratum (class of soil thickness) provided inconsistent species richness values. We simulated the efficiency of sampling strategies that included our 4 replicate plots and the 3 classes of soil thickness but with varying sampling effort within each stratum. The results indicated that a fairly large (74%) proportion of species would be recorded if strata were sampled using 5 sampling units (hence 15 samples per plot for a total of 4×15=60 samples). This study showed the need for adequate plot replication in soil macrofaunal biodiversity studies. Also, the main relevant factors of within-replicate plot spatial heterogeneity (e.g. soil, vegetation) should be accounted for through stratified sampling. The results showed that there is no way of reducing the local sampling effort below a certain level (here, 5 sampling units per stratum). 相似文献