无人直升机摄影测量系统的设计与验证

针对目前已有的无人机摄影测量系统存在的精度不高、依赖起降场地、续航能力差等问题,设计并实现了无人直升机摄影测量系统,该系统将Phase相机、Applanix POS设备集成在3轴稳定对地观测吊舱内,具有垂直起降、载荷量大、续航能力强、测量精度高等优势。在嵩山遥感定标场开展了测试飞行,结果表明：系统直接地理定位精度较高,可用于应急测图;在少量控制点参与下,系统定位精度远优于1∶500测图要求,可用于大比例尺测图,具有重要的推广应用价值。     

MEDIUM AND SMALL FORMAT PHOTOGRAPHY FOR THE MAINTENANCE OF NATIONAL MAPPING

In order to realise the full potential of photogrammetry for national map revision, photographic acquisition lead times and, where possible, costs must be significantly reduced. In this paper a review of alternative platform and camera configurations is made and tests are undertaken utilising simulated data and medium format data taken from an existing project. The results suggest that the medium format camera and helicopter combination may have much to offer while the small format camera and microlight aircraft systems have yet to be developed into an effective data acquisition and map compilation system.     

EARTH SATELLITE CAMERA SYSTEMS: RESOLUTION ESTIMATES AND MAPPING APPLICATIONS

Resolution functions which permit the comparison of camera systems considered for earth-orbiting satellite missions, indicate that a mapping camera (f = 300 mm) with approximately 20 m ground resolution at a scale of 1 : 750 000 would prove more useful for photogrammetric applications than any of the systems currently planned. In the absence of specific satellite missions for mapping purposes, the value of Skylab-type experiments could be greatly enhanced by the inclusion of a metric camera. ERTS-A with an estimated ground resolution on the order of 180 m was not intended as a cartographic system. In its present mode it does not meet the standards set by scientists for detailed studies of the earth's resources.     

A Structured Light System For Measuring Wounds

The lack of an accepted method of accurate and objective measurement of wound dimensions is a major obstacle to the assessment of effective wound management regimes. This paper addresses the problems associated with wound measurements and introduces a new instrument based on the principle of coded structured light. The instrument projects a sequence of parallel stripes of light onto the surface of the lesion. These patterns are observed by a video camera which is linked to a computer system where the images can be stored and processed. Using the positions of the focal points of the camera and the stripe projector, the computer calculates a three dimensional map of the observed scene by triangulation. This map is then used to reconstruct the original, healthy skin surface by cubic spline interpolation. The area of the reconstructed surface is the area of the wound. Its volume is sandwiched between the measured and the reconstructed surface. The system also calculates the depth and the circumference of the wound. The instrument measures the volume of the wound with a precision of about 5 per cent provided that the ratio of volume to area is greater than 4 mm.     

IMU辅助下的单目视觉坐标传递

针对管线测量中由于GNSS RTK卫星信号遮挡或测站不易架设等原因无法提供坐标的场景,本文提出了一种IMU辅助下的单目视觉坐标传递方法,用于延伸RTK测得的精密坐标。首先在两个已知的RTK点上架设相机拍摄图像,同时采集IMU数据;然后对图像进行特征提取和匹配,恢复帧间旋转、平移及尺度;最后三角化待测点,以获得待测点在真实尺度的相机坐标系下的坐标。受IMU静基座初始对准方法的启发,本文利用重力矢量和相机光心间矢量分别在地理坐标系和相机坐标系下的投影求解这两个坐标系间的旋转矩阵,进而求得待测点在地理坐标系下的三维坐标。相对于其他测量手段,本文方法灵活便捷、设备轻便、操作简单,且一次采集即可获取相机视场中的任意共视点坐标。试验结果表明,本文提出的坐标传递方法所得的平面坐标的误差平均值为0.12 m,高程误差的平均值为0.2 m。     

无人直升机低空数字摄影与影像测量技术

研究和建立了一套无人直升机低空数字摄影与影像测量系统。该系统以无人直升机为飞行平台,以数字相机为传感器,直接获取高分辨率数字影像,具有垂直升降、低空作业、自主飞行等特点。详细介绍了该系统的工作原理,总结了航空摄影关键参数的设计方法,同时,提出了视距网格的飞行模式,增强了系统安全性;利用试验场相机检定的技术,实现了非量测数字相机在摄影测量中的应用。最后介绍了该系统在15 km2大比例尺测绘工程中的应用情况以及综合精度检测结果。     

应用遥控直升机进行大比例尺地形测绘试验研究

采用遥控模型直升机作为航空摄影平台,无线数字摄像头摄影,按近景摄影测量方式进行处理,测绘目标区域小面积大比例尺地形图,作者将此方式称之为数字近景航空摄影测量。通过对面积为1.3km2的试验区域进行数字近景航空摄影测量,并与常规数字化测图成果进行对比分析。结果证明,采用近景航空摄影测量方法测绘小面积大比例尺地形图,其精度可满足摄影测量精度要求,并可提供数字正射影像图,同时减少测图成本。     

无人机大比例尺航测系统的研制及应用

以无人机作为低空遥感平台,将选择的轻小型量测相机与定制的小型双频高动态GPS进行搭载集成,并自主研制了一种三轴稳定云台装置,可保持无人机航摄时相机姿态的稳定,使获得的航空影像满足大比例尺测图的规范要求。将该系统应用于1：500大比例尺地形图测绘项目,结果表明该系统的成图精度完全可以满足国家航测内业成图规范及城市测量规范要求。     

带有差分GPS的多传感器无人直升机航测遥感系统

本文主要介绍作者在日本研制的一种基于无人直升机平台的多种传感器航测遥感系统,它直接采用GPS和IMU数据进行地理定位定向而不需要地面控制点。通过实飞数据对系统达到的几何精度进行了验证,结果表明该系统可用来测绘大比例尺地形图以及应用于其他相关领域。     

Monocular 3D scene reconstruction at absolute scale

In this article we propose a method for combining geometric and real-aperture methods for monocular three-dimensional (3D) reconstruction of static scenes at absolute scale. Our algorithm relies on a sequence of images of the object acquired by a monocular camera of fixed focal setting from different viewpoints. Object features are tracked over a range of distances from the camera with a small depth of field, leading to a varying degree of defocus for each feature. Information on absolute depth is obtained based on a Depth-from-Defocus approach. The parameters of the point spread functions estimated by Depth-from-Defocus are used as a regularisation term for Structure-from-Motion. The reprojection error obtained from bundle adjustment and the absolute depth error obtained from Depth-from-Defocus are simultaneously minimised for all tracked object features. The proposed method yields absolutely scaled 3D coordinates of the scene points without any prior knowledge about scene structure and camera motion. We describe the implementation of the proposed method both as an offline and as an online algorithm. Evaluating the algorithm on real-world data, we demonstrate that it yields typical relative scale errors of a few per cent. We examine the influence of random effects, i.e. the noise of the pixel grey values, and systematic effects, caused by thermal expansion of the optical system or by inclusion of strongly blurred images, on the accuracy of the 3D reconstruction result. Possible applications of our approach are in the field of industrial quality inspection; in particular, it is preferable to stereo cameras in industrial vision systems with space limitations or where strong vibrations occur.     

Utility of satellite data for land evaluation in land use planning for a part of Northern Karnataka

The study reported herein deals with the utility of satellite remote sensing techniques for land evaluation for agricultural land use planning. False colour composite of Landsat imagery in the scale of 1:250,000 was visually interpreted for physiography that formed the base for mapping soil and land resources in the field. The small-scale soil map thus prepared has thirteen map units with association of soil families. Soil and land resource units shown on these small-scale maps were evaluated for their suitability for growing sorghum crop by matching the relevant land qualities against the land requirements for sorghum. The land evaluation carried out for growing sorghum crop in the study area revealed that about 38.6 per cent is highly suitable (S1), 31.5 per cent moderately suitable (S2) and 24.5 per cent marginally suitable (S3). An area of about 5.4 per cent is not suitable, of which 3.0 per cent is currently not suitable (N1) and 2.4 per cent permanently not suitable for growing sorghum crop.     

Hyper Redundancy for Accuracy Enhancement in Automated Close Range Photogrammetry

A generic network design in close range photogrammetry is one where optimal multi-ray intersection geometry is obtained with as few camera stations as practicable. Hyper redundancy is a concept whereby, once the generic network is in place, many additional images are recorded, with the beneficial impact upon object point precision being equivalent to the presence of multiple exposures at each camera position within the generic network. The effective number of images per station within a hyper redundant network might well be in the range of 10 to 20 or more. As is apparent when it is considered that a hyper redundant network may comprise hundreds of images, the concept is only applicable in practice to fully automatic vision metrology systems, where it proves to be a very effective means of enhancing measurement accuracy at the cost of minimal additional work in the image recording phase. This paper briefly reviews the network design and accuracy aspects of hyper redundancy and illustrates the technique by way of the photogrammetric measurement of surface deformation of a radio telescope of 26 m diameter. This project required an object point measurement accuracy of σ  = 0·065 mm, or 1/400 000 of the diameter of the reflector.     

无人平台视觉导航算法验证仿真系统的设计与实现

近年来,基于视觉的导航和目标跟踪算法开始广泛应用于无人平台.针对各类视觉导航算法和综合任务方案在无人平台上实地测试风险性高、现场采集参数精度低、效率差等问题,设计并搭建了一套以高精度工控导轨平台、姿态控制云台、工业相机和模拟地形沙盘为主要部件的无人平台半物理仿真系统.引入OptiTrack光学运动捕捉设备对仿真系统真实...     

Bundle Adjustment For 35 mm Oblique Aerial Photography

The full provision of ground control points for oblique, small format photography used for mapping purposes is uneconomic because each photograph covers a small area of ground. This paper describes the implementation of a bundle adjustment program for 35 mm oblique aerial photography. Image co-ordinates are measured on enlarged prints, with a digitizing tablet driven by Carto MDSD software, and are then processed with the NLHBUNT program. The measurement system was proved by using vertical standard format photographs of a test block saturated with high quality ground control. Measurements taken with the MDSD system gave acceptable accuracy when compared with a set taken with a Zeiss P3 analytical workstation. A bundle adjustment was then carried out with the MDSD data; the results obtained compared satisfactorily with known ground values. A hand-held 35 mm Pentax LX camera was flown over the test site and three strips of 1:30 000 scale oblique photography were obtained. Following bundle adjustment, the empirical accuracy of derived co-ordinates was about 1.5 m in X, 3 m in Y and 2 m in Z. Factors affecting this accuracy are discussed and further developments of the system are proposed.     

便携式消费级无人机相机标定有效性评估

本文针对近年来在各行业中广泛使用的便携式消费级无人机开展了相机标定有效性研究,分别通过室内标定场和后处理软件对相机进行标定和自标定,在对比无相机标定、飞前相机标定、飞后相机标定和自标定迭代校正等方法所得成图精度后,对不同相机标定方案的有效性进行了评估。结果表明：各种方案成图总体精度差别不大;飞前、飞后相机标定与无相机标定的成图精度相当;自标定迭代校正的成图精度略高于其他方案。可见采用航拍照片自标定参数迭代校正的方法更适合于飞行控制精度和成像系统稳定性都不高的便携式消费级无人机相机标定。     

HIGH PRECISION LEVELLING OF MOTORWAYS. BY LOW LEVEL HELICOPTER SURVEY

Photogrammetrists are acutely aware that remote methods of survey are commonplace. However, it is only relatively recently that high precision levelling of the national motorway network has been conducted in this manner. There are now several competing methods available, all of which have gained some acceptance. This paper describes a low level aerial photographic method employing a helicopter as the platform. It begins with the reasons for the development, describes the system and methods involved, addresses the safety aspects, attempts to outline the necessity for the largest scale possible to maintain precision, analyses the potential developments and discusses the advantages and disadvantages compared with ground based systems.     

Helicopter Supported Photogrammetric Survey of Ramsberg Castle

Ramsberg Castle is to be restored and renovated to allow a new use of the building. This requires extensive structural and architectural analyses based upon metric documentation. The façades of the castle were recorded photogrammetrically. Photography from the ground was impossible due to the steep terrain on three sides of the building. For this reason, the photographs were taken from a helicopter. A 4 × 5 inch Linh of Metrika réseau camera was used.
Because of the adverse topography, only a few control points could be determined by on-site theodolite measurement. Therefore the control network was achieved by means of photogrammetric bundle triangulation. Stereorestitution was performed using an analytical plotter connected with a CAD system. Drawings at 1:50 scale were then derived from the as-built CAD model.     

无人直升机面阵影像高精度对地定位

为提高无人机对地定位精度,必须对系统进行几何标定与补偿。首先进行了直接地理定位实验,检验系统在不经过任何标定时的直接地理定位精度;然后进行了自由网光束法平差实验,以验证无地面控制点时系统的定位精度;最后进行了POS辅助自检校光束法平差,对内方位元素变化、相机畸变、IMU安置角进行标定和补偿,并验证了系统误差补偿后的直接地理定位精度。实验结果表明,未经几何标定的无人直升机直接地理定位的精度可满足应急条件下测绘保障要求;少量地面控制点的辅助下定位精度远优于1∶500比例尺地形图测图的要求,可用于常规测绘生产;系统误差补偿后,直接地理定位精度有明显提升:平面精度提高46.37%,高程精度提高62.49%;系统误差标定和补偿方法正确、有效,无人直升机具有很好的测绘应用前景。     

轻便型移动测量系统在大比例尺DOM质检中的应用

为研究车载移动测量技术在大比例尺DOM质量检验中的应用,本文以一种轻便型车载移动测量系统为例,首先介绍了系统及其误差来源,并通过已有数据检测分析系统的测量精度,继而利用该系统对城区0.2 m分辨率试验DOM进行点云采集、检测点提取和精度评定,结果表明利用轻便型移动测量系统进行大比例尺DOM的质量检验是可行的。     

Urban cadastral mapping using very high resolution remote sensing data

With growing urban expanses, one of the pre-requisites for effective governance is Urban Information Systems (UIS) with content down to individual properties (and individuals). The basic input i.e., a map, in UIS should show individual property boundaries showing the plan outline of all structures existing within, at a scale of 1:1000 and larger with sub-metre to centimeters planimetric and geometric accuracy. With very high resolution remote sensing data of the order of 1m available in hand, it is possible to prepare maps with high resolution spatial content. The present exercise demonstrates a method of preparing a geometrically and planimetrically accurate urban cadastral map on very large scale for a small area of about 5 sq km. IKONOS merged data with 1m resolution is used for the purpose. Mapping was done in conjunction with on-site measurements and sketches. Guides are used to maintain shape symmetry and accuracy of buildings and other features. Working out cost of mapping per unit area is another objective in the present exercise. For want of fully or semi-automatic methods of information extraction from very high resolution remote sensing data, it is imperative that mapping should be carried out in conjunction with some on-site measurements wherever necessary.