Image matching as a data source for forest inventory – Comparison of Semi-Global Matching and Next-Generation Automatic Terrain Extraction algorithms in a typical managed boreal forest environment

Image matching is emerging as a compelling alternative to airborne laser scanning (ALS) as a data source for forest inventory and management. There is currently an open discussion in the forest inventory community about whether, and to what extent, the new method can be applied to practical inventory campaigns. This paper aims to contribute to this discussion by comparing two different image matching algorithms (Semi-Global Matching [SGM] and Next-Generation Automatic Terrain Extraction [NGATE]) and ALS in a typical managed boreal forest environment in southern Finland. Spectral features from unrectified aerial images were included in the modeling and the potential of image matching in areas without a high resolution digital terrain model (DTM) was also explored. Plot level predictions for total volume, stem number, basal area, height of basal area median tree and diameter of basal area median tree were modeled using an area-based approach. Plot level dominant tree species were predicted using a random forest algorithm, also using an area-based approach. The statistical difference between the error rates from different datasets was evaluated using a bootstrap method.Results showed that ALS outperformed image matching with every forest attribute, even when a high resolution DTM was used for height normalization and spectral information from images was included. Dominant tree species classification with image matching achieved accuracy levels similar to ALS regardless of the resolution of the DTM when spectral metrics were used. Neither of the image matching algorithms consistently outperformed the other, but there were noticeably different error rates depending on the parameter configuration, spectral band, resolution of DTM, or response variable. This study showed that image matching provides reasonable point cloud data for forest inventory purposes, especially when a high resolution DTM is available and information from the understory is redundant.     

机载POS直接地理定位软件AeroDG的设计与实现

AeroDG是专门针对机载POS直接地理定位方法而设计开发的数据处理软件。本文从软件的功能需求入手，重点讨论了软件的 设计思路和关键技术，同时详细介绍了软件实现的主要功能。     

Kinematics of a deep-seated landslide derived from photogrammetric, GPS and geophysical data

The deep-seated landslide located at the intersection of the Gradenbach and Möll valleys near Döllach, Austria, has been the target of many previous investigations [Kronfellner-Kraus, G., 1980. Neue Untersuchungsergebnisse in Wildbächen — Der Talzuschub in Abhängigkeit von Niederschlägen. Int. Symp. Interpraevent Bad Ischl 1: 179–192; Weidner, S., Moser, M., Lang, E., 1998. Influence of hydrology on sagging of mountain slopes (“Talzuschübe”) — New results of time series analysis. 8th International IAEG Congress, Vancouver, Canada, Balkema, Rotterdam, 1259–1266; Weidner, S., 2000. Kinematik und Mechanismus tiefgreifender alpiner Hangdeformationen unter besonderer Berücksichtigung der hydrologischen Verhältnisse. Dissertation, Friedrich–Alexander-Universität Erlangen–Nürnberg, 246.]. In this paper, photogrammetric, GPS and geophysical data have been utilized to derive a constraint on the kinematics of the sagging process. The photogrammetric models have been based on aerial photographs from 1962 and 1996. Displacement vectors of about 50 individual characteristic points have been determined; these clearly show the area of the sagging slope. From 1999 to 2004, eleven GPS campaigns have been carried out, yielding very accurate displacement vectors at four monitoring points. Information about the internal structure of the slope was determined using seismic surveys.

The displacements observed by photogrammetry and GPS have shown a rather uniform movement of the whole sagging slope, with a slight longitudinal compression of 0.6%. In order to extend the kinematic consideration to 3D, a special form of the equation of continuity (conservation of mass) has been applied to the 1962–1996 photogrammetric data, together with the cross-sections derived from the seismic data. The average velocities through cross-sections have been calculated by integrals of the mass-balance above and below these cross-sections. Changes of the total rock mass, due to accumulation and especially to erosion, as well as an overall compaction of 1.5% between 1962 and 1996, have been considered. The calculated average velocities through a cross-section and the surface velocities independently determined by photogrammetry agree within an uncertainty of 15%. The results indicate a block movement with shear concentration at the basal sliding surface.     

摄影测量学的教学改革探讨与实践

随着计算机技术、空间技术和信息技术的飞速发展,POS、无人机、LiDAR等在摄影测量领域的应用日趋广泛。如何使"摄影测量学"的教学体系和教学方法与摄影测量的时代特征相适应,满足社会对创新型和实践型摄影测量人才的需求,是一个值得摄影测量教育工作者关注的问题。为此,文章以社会调研和作者的教学经验为基础,分解"摄影测量学"的教学目标,并对教学内容、教学方法、实践教学等方面的改革进行系列探索与实践,取得了较好的教学成效。     

Edgar Hynes Thompson: aerial triangulation and ISP Commission III

This author worked with E. H. Thompson in several different contexts in the course of his military and civilian career, notably in developing Thompson's ideas about analytical aerial triangulation into a production system at the Ordnance Survey and later as a lecturer under Thompson at University College London and as Secretary of ISP Commission III when Thompson was Commission President. This essay thus stands as a separate contribution from a close colleague.     

The Photogrammetric Society: 1952–2001

A scholarly account of the formative discussions, the founding and the first 20 years of the Photogrammetric Society was published in 1971 and republished in 1974. This present review concentrates on the latter years of the life of the Photogrammetric Society prior to its merger with the Remote Sensing Society in 2001.
The authors joined the Photogrammetric Society in 1960 and were conspicuous in its affairs for many years. Although both occupied the Society's presidential chair, they also fulfilled several other roles in its efficient management. Atkinson's first contribution to the Photogrammetric Record was published in 1968 and Newton's in 1971.     

基于普通数码相机的近景摄影测量方法与精度的试验研究

普通数码相机由于体积小、重量轻、价格低廉、像素几何位置精度高、影像可直接输入计算机进行处理等优点备受人们青睐。随着数字摄影测量技术的发展,数码相机分辨率的不断提高,人们开始考虑能否将普通数码相机应用于工程实践。本文以普通数码相机作为影像信息的获取手段,就控制点的数量、分布、精度、影像获取及其量测方法、数据处理解算方法、解算精度等问题进行了研究。     

Extracting ecological information from oblique angle terrestrial landscape photographs: Performance evaluation of the WSL Monoplotting Tool

While aerial photography and satellite imagery are the usual data sources used in remote sensing, land based oblique photographs can also be used to measure ecological change. By using such historical photographs, the time frame for change detection can be extended into the late 1800s and early 1900s, predating the era of aerial imagery by decades. Recent advancements in computing power have enabled the development of techniques for georeferencing oblique angle photographs. The WSL Monoplotting Tool is a new piece of software that opens the door to analyzing such photographs by allowing for extraction of spatially referenced vector data from oblique photographs. A very large repeat photography collection based on the world's largest systematic collection of historical mountain topographic survey images, the Mountain Legacy Project, contains >6000 high resolution oblique image pairs showing landscape changes in the Rocky Mountains of Alberta between ca. 1900 – today. We used a subset of photographs from this collection to assess the accuracy and utility of the WSL Monoplotting Tool for georeferencing oblique photographs and measuring landscape change. We determined that the tool georeferenced objects to within less than 15 m of their real world 3D spatial location, and the displacement of the geographic center of over 121 control points was less than 3 m from the real world spatial location. Most of the error in individual object placement was due to the angle of viewing incidence with the ground (i.e., low angle/highly oblique angles resulted in greater horizontal error). Simple rules of control point selection are proposed to reduce georeferencing errors. We further demonstrate a method by which raster data can be rapidly extracted from an image pair to measure changes in vegetation cover over time. This new process permits the rapid evaluation of a large number of images to facilitate landscape scale analysis of oblique imagery.     

基于POS系统直接地理定位快速制作DOM

基于POS系统辅助航空摄影测量技术可以在航空摄影的同时直接获取曝光瞬间航摄仪的空间位置和姿态参数，通过对集成系 统误差进行检校与改正，即可获得用于正射影像图制作的高精度外方位元素。本文结合实际生产试验，较系统地介绍了采用该技术 进行正射影像图快速制作的方法，并对关键技术环节进行分析，总结了基于POS系统直接地理定位快速制作DOM的方法和流程。