As a convenience to ASPRS members in-press peer reviewed articles approved for publication in forthcoming issues of PE&RS have been made available for members of the society.

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May 2016 Issue

Camera Self-Calibration with Lens Distortion from a Single Image

Dan Liu Xuejun Liu and Meizhen Wang

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This paper presents an effective approach for self-calibration with lens distortion using a single image combined with geometric constraints including vanishing points and ellipses. To improve the accuracy of self-calibration radial distortion and distortion center are included in the calibration procedure. First assuming image center as the symmetric center the first radial distortion coefficient and vanishing points are simultaneously optimized from line segments in the image. Second by utilizing the optimized vanishing points and extracted ellipse principal distance and principal point are estimated. Last distortion center is set as the current calculated principal point and the above steps are then repeated until the principal point reaches a stable solution. Extensive quantitative and qualitative studies of the approach are performed. The experiments pertaining to simulated and real images demonstrate that the approach is effective and suitable and that the approach obtains satisfactory results.

Camera Self-Calibration with Lens Distortion from a Single Image


Craig Mahoney Chris Hopkinson Alex Held Natascha Kljun and Eva van Gorsel


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Variations in laser properties and data acquisition times introduced inconsistencies in Geoscience Laser Altimeter System (GLAS) data. The effect of data inconsistencies on two GLAS height retrieval methods from three study sites are investigated and validated against airborne laser scanning (ALS) percentile heights from three data sources: all/first return point clouds and raster canopy height models. GLAS/ALS controls were established as a basis against which the influence of laser number transmission energy and seasonality were assessed through comparison statistics. The favored GLAS height method best compared with ALS 95th percentile heights from an all return point cloud. Optimal GLAS data (R2 = 0.69 RMSE = 8.10 m) were noted when GLAS acquired data during summertime from high energy laser three transmissions. As GLAS data can be used in global biomass assessments there is a need to understand and quantify the influence of these data inconsistencies on canopy height estimates.

A Novel Automatic Structural Linear Feature-based Matching Method Based on New Concepts of Mathematically-Generated-Points and Lines

Somayeh Yavari Mohammad Javad Valadan Zoej Mahmod Reza Sahebi and Mehdi Mokhtarzade

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This paper investigates reliable automatic high resolution image to map matching using a novel structural linear feature-based matching (SLIM) method. The main components used by this method are the specific patterns as well as the lines and points generated mathematically. These components are produced by extension and intersection of extracted line-segments. Due to the high numbers of extracted line-segments in both image and object space the number of possible patterns is very high. In order to decrease the search space the innovative SLIM method is performed in three main phases. In the first phase using a new weighting procedure only optimum numbers of high-qualified well-distributed patterns which are more likely to have any correspondence in object space are selected. In the second phase the aim is to find a pair with maximum numbers of conjugate lines. To do so all the possible patterns in object space are screened for each selected image pattern using four predefined geometric criteria. Simultaneously the correspondence of the other crossing lines is also determined in the same manner. In third phase the pair with maximum numbers of matched-lines is selected among all the results of second phase. Additionally the final-phase is done to increase the amount of correctly matched-lines. The main contribution of this investigation is automatic and correct matching of linear features with no need to any initial information. Additionally the end-points of the corresponding lines are not necessarily conjugate points. The results show the high potential of the proposed method in terms of accuracy reliability automation and time reduction even in images with repetitive patterns or a high numbers of outliers.


Extraction of Urban Impervious Surface UsingTwo-Season WorldView-2 Images: A Comparison

Cai Cai Peijun Li and Huiran Jin

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Although multispectral images acquired during the summer season have been used extensively in impervious surface extraction with relatively high accuracy the area of impervious surface extracted is generally underestimated. In this study a quantitative comparison of urban impervious surface extraction was conducted using WorldView-2 images of the summer and winter seasons over two urban areas in a temperate region of Northern China. A hierarchical object-based classification method was adopted to extract urban impervious surfaces. The results showed that the impervious surface extraction from the winter image achieved an accuracy comparable with that from the summer image. However the area of impervious surface extracted from the winter image was much greater than that from the summer image which was mainly attributed to seasonal variations of deciduous trees. Therefore winter images are recommended for impervious surface mapping in temperate regions using very high resolution images.