航空录像系统及其在森林保健中的应用

本文介绍了航空录像系统及其在森林保健中的应用情况；探讨了航空录像的技术特点，包括：图像获取系统、导航装备、实验室图像处理系统和其它航空录像系统配套设备和技术；并对发展我国的航空录像技术提出了建议。     

Change detection using bi-temporal aerial photographs and registration at the stand level

There is a trend to continuously update forest data in forest management planning systems. Thus, changes in forest stands caused by, e.g. operations and storm damages should be detected in order to ensure the accuracy of forest data and beneficial decisions related to the treatments of the stands. This justifies the application of aerial photographs in change detection as being reasonable because they are already used in forest management planning. This study presents a semi-automatic method based on bi-temporal aerial photographs and registration at the stand and segment levels for the detection of changes in boreal forests. Linear stepwise discriminant analysis and the non-linear k-nearest neighbour (k-NN) method were tested and statistically compared in classification. The classification results at the stand level were found to be better than at the segment level. Compared to previous studies, the results of this study demonstrate remarkable improvement in the classification accuracy of moderate changes. The results showed that change detection substantially improved when the registration at the stand level was used, especially in the detection of thinned stands. To some extent, the method can be already applied operationally.     

Increasing the use of expert opinion in forest characterisation approaches based on LiDAR data

Context

Forest structure characterisation approaches using LiDAR data and object-based image analysis remain scarce to forestry agencies as these automated procedures usually require the use of expensive software and highly skilled analysts. The integration of forest expert opinion into semi-automated approaches would simplify the access of forest managers to new technologies and would allow the incorporation of personal experience and the introduction of specific forest management criteria.

Aim

The aim of this study is to explore new alternatives to a previously published automated approach based on LiDAR data and object-based image analysis.

Methods

We compare four approaches, ranging from null to high incorporation of expert opinion and from fully automated to fully manual. These four approaches consist of three stages: (1) forest stand identification from LiDAR models, (2) forest stand classification into forest structure classes (manual and based on cluster analysis), and (3) validation.

Results

Quantitative attributes for validation (i.e. hypsographs and percentiles) provided slightly lower degree of separability for forest structure classes, in the mixed procedures with increasing incorporation of expert opinion than for the fully automated approach.

Conclusions

The new mixed approaches proposed are comparable to the automated procedures for the characterisation of forest structure in heterogeneous pine forest stands. They also offer additional advantages: (1) they make it possible to give a specific management focus and (2) they provide accessibility by the forest managers to the source of LiDAR information.     

多极化星载SAR森林覆盖变化检测方法

【目的】利用多极化星载SAR数据,分析后向散射强度比值影像的概率密度分布特征,融合后向散射强度信息和影像空间上下文信息,提出一种具有较高检测正确率及较低虚警率和漏警率的森林覆盖变化检测方法,为多极化SAR卫星数据的业务化应用提供技术支撑。【方法】将"2期分别分类森林覆盖变化检测法"(CBFC)与"贝叶斯最大期望-马尔科夫随机场(EM-MRF)变化检测法"相结合,首先采用阈值分割法分别对2期多极化SAR影像进行森林-非森林分类得到初始森林覆盖变化图,然后以初始森林覆盖变化图作为训练数据对多极化比值影像进行Fisher特征变换和EM-MRF分类处理,2个时相的HH、HV极化比值影像经Fisher特征变换转化为一个综合差异影像,输入EM-MRF进行迭代分类得到森林覆盖变化检测结果。以黑龙江省逊克县为试验区,以2期ALOSPALSAR双极化数据为SAR遥感数据,以对2期Landsat-5影像、高空间分辨率遥感影像进行目视解译得到的森林覆盖变化图为参考,对本研究提出方法的有效性与CBFC方法及直接用CBFC提取的森林覆盖变化检测图掩膜EM-MRF地表覆盖变化检测图方法(CBFC-EM-MRF)进行比较评价。【结果】通过Fisher特征变换得到的差异影像可有效增强森林覆盖变化、未变化类别的对比度;CBFC通过阈值分割法进行森林-非森林分类,提取的森林覆盖变化图中出现很多面积很小的虚警检测,漏警率也很高,而本研究提出方法通过MRF加入影像空间上下文信息,提高了检测结果的空间连贯性,森林覆盖变化检测虚警率为1.58%,漏警率为11.87%,正确率为98.36%,检测效果和精度明显优于CBFC和CBFC-EM-MRF。【结论】多极化星载SAR森林覆盖变化检测方法具有收敛性好、检测结果可信度高、需要用户交互较少等特点,对我国高分三号及未来其他多极化SAR卫星的森林资源监测业务应用具有重要参考价值。     

Comparing biophysical forest characteristics estimated from photogrammetric matching of aerial images and airborne laser scanning data

Recent development in aerial digital cameras and software facilitate the photogrammetric point cloud as a new data source in forest management planning. A total of 151 field training plots were distributed systematically within three predefined strata in a 852.6 ha study area located in the boreal forest in southeastern Norway. Stratum-specific regression models were fitted for six studied biophysical forest characteristics. The explanatory variables were various canopy height and canopy density metrics derived by means of photogrammetric matching of aerial images and small-footprint laser scanning. The ground sampling distance was 17 cm for the images and the airborne laser scanning (ALS) pulse density was 7.4 points m^–2. Resampled images were assessed to mimic acquisitions at higher flying altitudes. The digital terrain model derived from the ALS data was used to represent the ground surface. The results were evaluated using 63 independent test stands. When estimating height in young forest and mature forest on poor sites, the root mean square error (RMSE) values were slightly better using data from image matching compared to ALS. However, for all other combinations of biophysical forest characteristics and strata, better results were obtained using ALS data. In general, the best results were found using the highest image resolution.     

基于人工智能深度学习的卫星影像分类研究

以芒市2019年卫星影像及2019年林地一张图成果为研究对象,基于深度学习的卫星影像分类研究,构建森林资源分类识别模型,以提高森林资源监测能力.将裁剪后的芒市2019年卫星影像分有林地、灌木林地、未成林地及耕地、建设用地5个类别导入自定义的ResNet18模型进行深度学习,并对学习结果进行验证.实验结果显示,在模型训练...     

广东珠江三角洲地区森林资源连续清查管理系统的设计与开发

以广东珠江三角洲地区1997-2007三次森林连续清查数据为基础,基于ArcEngine组件、C#语言、ArcSDE空间数据引擎、SQL Server 2005数据库和.NET开发环境等计算机技术,设计并开发了符合用户需求和贴近本行业的森林资源连续清查管理系统。该系统实现了用户管理、地图基本操作、图层处理、查询统计、属性编辑、专题图、图形编辑和图像输出等功能,能满足森林资源连续清查图形、数据更新的要求。本系统在珠江三角洲地区森林资源连续清查数据的管理方面进行了有益的探索,是一个GIS组件式二次开发的应用案例。     

苏联森林经理工作的现状及发展方向

本文从5个方面论述了最近10多年来,苏联传统的森林经理工艺的进展与改革:(1)伐区工艺改革(包括伐区拨交与验收);(2)各种森林资源调查方法的研究与使用;(3)全苏小班数据库的建立及自动化检索系统的研制;(4)森林经理制图自动化系统的开发与应用;(5)遥感与电算技术发展迅速。文章还介绍了苏联森林经理技术发展的新动向。     

基于高分二号遥感数据的森林自然度等级划分

以地面样点为基础的森林自然度评价方法很难获得区域范围森林自然度等级,针对该问题,提出了利用高分遥感卫星影像数据,划分区域范围森林自然度等级的方法。以湖北竹山县九华山林场为试验区域,在选取研究区典型样地的基础上,结合高分二号(GF-2)遥感影像数据的特点,从GF-2影像上提取遥感光谱、纹理等特征并结合地形特征,采用随机森林算法在大尺度范围对九华山林场森林自然度等级进行分类研究。结果发现:以GF-2数据为基础提取的植被指数、光谱、纹理等特征与地形特征结合,采用随机森林算法可较好地划分森林自然度等级,总体分类精度高达93.97%,Kappa系数为0.91。对森林自然度等级影响最重要的6个特征因子为高程、坡向、坡度、纹理均值、光谱主成分变化分量和归一化植被指数(NDVI)。结果表明,基于遥感影像提取的特征和地形特征结合进行森林自然度等级划分的研究方法具有可行性,为大面积区域的森林自然度等级划分奠定基础。     

Analysis of forest cover change at Khadimnagar National Park,Sylhet, Bangladesh,using Landsat TM and GIS data

We mapped the forest cover of Khadimnagar National Park （KNP） of Sylhet Forest Division and estimated forest change over a period of 22 years （1988-2010） using Landsat TM images and other GIS data. Supervised classification and Normalized Difference Vegetation Index （NDVI） image classification approaches were applied to the images to produce three cover classes, viz. dense forest, medium dense forest, and bare land. The change map was produced by differencing classified imageries of 1988 and 2010 as before image and after image, respectively, in ERDAS IMAGINE. Error matrix and kappa statistics were used to assess the accuracy of the produced maps. Overall map accuracies resulting from supervised classification of 1988 and 2010 imageries were 84.6% （Kappa 0.75） and 87.5% （Kappa 0.80）, respec- tively. Forest cover statistics resulting from supervised classification showed that dense forest and bare land declined from 526 ha （67%） to 417 ha （59%） and 105 ha （13%） to 8 ha （1%）, respectively, whereas medium dense forest increased from 155 ha （20%） to 317 ha （40%）. Forest cover change statistics derived from NDVI classification showed that dense forest declined from 525 ha （67%） to 421 ha （54%） while medium dense forest increased from 253 ha （32%） to 356 ha （45%）. Both supervised and NDVI classification approaches showed similar trends of forest change, i.e. decrease of dense forest and increase of medium dense forest, which indicates dense forest has been converted to medium dense forest. Area of bare land was unchanged. Illicit felling, encroachment, and settlement near forests caused the dense forest decline while short and long rotation plantations raised in various years caused the increase in area of medium dense forest. Protective measures should be undertaken to check further degradation of forest at KNP.     

Clear-cut Detection in Boreal Forest Aided by Remote Sensing

The study compares the applicability of different remote sensing data and digital change detection methods in detecting clear-cut areas in boreal forest. The methods selected for comparisons are simple and straightforward and thus applicable in practical forestry. The data tested were from Landsat satellite imagery and high-altitude panchromatic aerial orthophotographs. The change detection was based on image differencing. Three different approaches were tested: (1) pixel-by-pixel differencing and segmentation; (2) pixel block-level differencing and thresholding; and (3) presegmentation and unsupervised classification. The study shows that the methods and data sources used are accurate enough for operational detection of clear-cut areas. The study suggests that predelineated segments or pixel blocks should be used for image differencing to decrease the number of misinterpreted small areas. For the same reason the use of a digital forest mask is crucial in operational applications.     

三江并流世界自然遗产地的遥感分析

从陆地卫星TMD131/41图像上可以看出,三江(怒江、澜沧江和金沙江)并流的真面目。通过遥感判读、利用判读的野外概率抽样和GIS处理技术,对三江并流进行地理景观分析。该三江并流地具有地质地貌的独特性、生态系统的完整性、生物资源的多样性和自然景观的奇特性。通过对三江并流自然遗产的分析得知森林植被是生态、景观和生物多样性保护的基础。此外,科学管理也是遗产保护的重要措施。     

雷达遥感在热带林经营中的应用

随着全球热带雨林面积的急剧减少，对热带林的经营管理日益得到人类的关注。雷达系统以其全天侯、全天时、穿透性等功能成为支持森林可持续经营中信息采集的重要工具。文中介绍了用现有技术做雷达影像分析，以及这些技术应用于全球水平、国家水平和森林经营单位水平的森林资源评价和森林资源监测的潜力。     

Forest Re-growth Since 1945 in the Dadia Forest Nature Reserve in Northern Greece

The Dadia forest complex, in the Evros prefecture, in north eastern Greece was designated as a nature reserve in 1980 in order to protect the black vulture (Aegypius monachus) and other raptors. In this paper, the impacts of the protection on the forest growth were assessed using geographic information system (GIS) technologies. The major requirement for almost all research needed for sustainable forest management is extensive and intensive monitoring. GIS is a convenient tool for integrating remotely sensed data and various other kinds geo-referenced data. Detailed spatial and temporal change patterns of the land uses in the area were quantified by interpreting aerial photographs of the years 1945 and 1973 and a satellite image of 2001. The results showed that the rate of forest growth is significantly larger during the second period (1973–2001) than during the earlier one (1945–1973). This is mostly due to the introduction, in 1980, of a protection regime, including two high-protection core areas, and a buffer zone. From 1945 to 2001 the openings which are important as hunting biotopes for raptors were significantly decreased. Apart from the protection of the area that was played an important role in the forest changes the effects of various landscape parameters (elevation, slope, distance from the roads and urban areas, aspect, soil depth, geology, erosion and forest density) on these changes were examined.     

3S技术在城市绿地系统中的应用探讨——以园林绿地信息采集与管理中的应用为例

以构建城市园林绿地系统的空间数据库为切入点,探讨了以遥感影像(RS)和全球卫星定位系统(GPS)为信息源,以地理信息系统(GIS)为平台的城市园林绿地系统数字化管理的应用技术。根据航空像片和高分辨率卫星影像数据特点及数据采集中应注意的问题,提出了城市绿地系统影像库、矢量库和属性库的空间数据库建库的方法与对策。通过对不同用户城市园林绿地系统空间数据库的使用特点分析,设计了具体的应用思路。     

Detection of Windthrow in Mountainous Regions with Different Remote Sensing Data and Classification Methods

After a disastrous storm event, quick and reliable information on the extent of forest damage is required. This study evaluated different remote sensing data and methods to detect windthrown forests in mountainous regions as an alternative to the manual analysis of aerial images or terrestrial methods. To this end, both optical satellite sensors (Landsat-7, Spot-4 and Ikonos) and synthetic aperture radar (SAR) data at various frequencies (X-, L-, P- and C-band) were evaluated, and classifications of the windthrown forests were performed. This study was designed to state the advantages and disadvantages of the investigated data and methods. Classification results were compared with aerial images which were interpreted manually on a stereoscopic base. The study showed that the manual interpretation of Ikonos data revealed the most accurate results, followed by an automatic classification of Spot-4 data. Except for ERS-1/2 data, which are too inaccurate in mountainous regions, and SAR P-band data, all sensors and methods investigated have different advantages, so the choice of a specific sensor and method will depend on the question being answered.     

Vegetation inventory of a temperate biosphere reserve in China by image fusion of landsat TM and SPOT HRV

Vegetation cover types on Changbai Mountain, a natural biosphere reserve (2,000 km²) in northeast China, were derived by using multisensor satellite imagery fused with Landsat TM and SPOT HRV-XS. DEM data were used for improving classification accuracy. Cover types were classified into 20 groups. Bands 4 and 5 of Landsat TM image acquired on July 18, 1997, and band 1 of SPOT HRV-XS image acquired on Oct. 19, 1992, were fused to a false color image, and maximum likelihood supervised classification was performed. Data fusion showed high accuracy of identification, compared to individual images. The overall accuracy of classification of individual images by SPOT HRV-XS reached 56%, and TM 66%, while the fused data set provided accuracy of about 78%, which was raised to 81% after recoding by using DEM. There were five vegetation zones on the mountain, from the base to the peak: hardwood forest zone, mixed forest zone, conifer forest zone, birch forest zone, and tundra zone. Spruce-fir dominated conifer forest was the most prevalent (nearly 50%) vegetation type, followed by Korean pine and mixed forest (17%) and larch forest (5%). HRV image taken in leaf-off season is useful for discriminating forest from non-forest, and evergreen forest from hardwood forest, while the summer image (TM) provides detailed information on the difference in similar vegetation types, like hardwood forest with different compositions.     

基于3S技术的林业信息系统设计

在对目前林业信息系统进行调查、分析的基础上,设计了基于3S技术的林业信息系统,并对系统的主要功能模块和关键技术作了详细的记述。对其系统功能模块的应用分析表明,该系统将GIS空间分析、电子地图匹配和GPS导航、RS影像数据相结合,从而实现了林业资源管理工作的信息化、科学化和智能化。     

0.5M分辨率航摄数字影像数据在森林资源规划设计调查中的应用

以0.5 M分辨率航摄数字影像数据为基础,结合以往调查设计及经营资料,对森林资源规划设计调查小班的部分因子进行判读,探讨高分辨率航摄数字影像数据在森林资源规划设计调查中的应用,结果表明:利用0.5M分辨率航摄数字影像数据进行小班因子判读,可以作为小班因子调查的辅助手段,并可显著提高小班调查质量及效率。     

无人机低空遥感在复杂山地森林景区实景三维构建中的应用——以南岭国家森林公园为例

真实三维场景可真实地反映森林景区的地形地貌特征,为森林景区科学管理、生态监测、景观规划及虚拟可视化等提供数据支撑和技术依据。文章以南岭国家森林公园为例,分析了复杂高山地形特征和无人机特性,研究一种利用复合翼无人机对高山景区进行影像采集,建立实景三维模型、表面模型DSM和正射影像图DOM的方法,实现对南岭森林景区75 km~2真实三维场景构建,对场景精度和成果应用进行了分析。结果表明,利用复合翼无人机进行高山景区航拍,既解决了起飞降落问题,又提升了航拍时效性和可靠性;突破传统二维成果的局限性,提供三维模型、DSM和DOM等成果,提升景区可视化管理、森林调查及应用分析等能力。