Accuracy Assessment of a Photogrammetric UAV Block by using Different Software and Adopting Diverse Processing Strategies

Casella, Vittorio; Chiabrando, Filiberto; Franzini, Marica; Manzino, Ambrogio

doi:10.5220/0007710800770087

Cited by 7 publications

(6 citation statements)

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“…This command allowed to calibrate the images and to align them in a local reference system according to several parameters. According to the previous tests reported in [48], in order to improve the achieved results after the bundle block adjustment, a more complex calibration model was used. The employed calibration model was the one reported in [49], hereafter called F15P7.…”

Section: Micmacmentioning

confidence: 99%

Accuracy Assessment of a UAV Block by Different Software Packages, Processing Schemes and Validation Strategies

Casella

Chiabrando

Franzini

et al. 2020

IJGI

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Unmanned aerial vehicle (UAV) systems are heavily adopted nowadays to collect high-resolution imagery with the purpose of documenting and mapping environment and cultural heritage. Such data are currently processed by programs based on the Structure from Motion (SfM) concept, coming from the computer vision community, rather than from classical photogrammetry. It is interesting to check whether some widely accepted rules coming from old-fashioned photogrammetry still holds: the relation between accuracy and ground sampling distance (GSD), the ratio between the vertical and horizontal accuracy, accuracy estimated on ground control points (GCPs) vs. that estimated with check points (CPs) also in relation to their ratio and distribution. To face the envisaged aspects, the paper adopts a comparative approach, as several programs are used and numerous configurations considered. The paper illustrates the dataset adopted, the carefully tuned processing strategies and bundle block adjustment (BBA) results in terms of accuracy for both GCPs and CPs. Finally, a leave-one-out (LOO) cross-validation strategy is proposed to assess the accuracy for one of the proposed configurations. Some of the reported results were previously presented in the 5th GISTAM Conference.

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Section: Micmacmentioning

confidence: 99%

Accuracy Assessment of a UAV Block by Different Software Packages, Processing Schemes and Validation Strategies

Casella

Chiabrando

Franzini

et al. 2020

IJGI

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“…Only the four multispectral channels were considered, having 6.8 cm GSD; higher resolution RGB imagery was disregarded, as it is recorded in the JPEG format with a high compression factor, and has low quality compared to photogrammetry requirements. The processing followed the usual pipeline [35,36]: image alignment, tie point extraction, manual measurement of GCPs and CPs, bundle block adjustment (BBA), generation of dense point clouds, digital surface modeling (DSM), and creation of orthomosaic and reflectance maps. The software allows only one set of calibration target images to be used per project, so the photogrammetric processing followed a single-block approach.…”

Section: The Photogrammetric Processingmentioning

confidence: 99%

Geometric and Radiometric Consistency of Parrot Sequoia Multispectral Imagery for Precision Agriculture Applications

et al. 2019

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This paper is about the geometric and radiometric consistency of diverse and overlapping datasets acquired with the Parrot Sequoia camera. The multispectral imagery datasets were acquired above agricultural fields in Northern Italy and radiometric calibration images were taken before each flight. Processing was performed with the Pix4Dmapper suite following a single-block approach: images acquired in different flight missions were processed in as many projects, where different block orientation strategies were adopted and compared. Results were assessed in terms of geometric and radiometric consistency in the overlapping areas. The geometric consistency was evaluated in terms of point cloud distance using iterative closest point (ICP), while the radiometric consistency was analyzed by computing the differences between the reflectance maps and vegetation indices produced according to adopted processing strategies. For normalized difference vegetation index (NDVI), a comparison with Sentinel-2 was also made. This paper will present results obtained for two (out of several) overlapped blocks. The geometric consistency is good (root mean square error (RMSE) in the order of 0.1 m), except for when direct georeferencing is considered. Radiometric consistency instead presents larger problems, especially in some bands and in vegetation indices that have differences above 20%. The comparison with Sentinel-2 products shows a general overestimation of Sequoia data but with similar spatial variations (Pearson’s correlation coefficient of about 0.7, p-value < 2.2 × 10−16).

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“…On that basis, 3D scene accuracy is improved to a greater extent, and operational risks and the dependence on GCPs are reduced [27]. Most existing studies for 3D scene accuracy are based on combining different data processing software and different GCPs layout schemes to accurately assess a single image dataset by using checkpoints [28,29]. However, when RTK UAVs are adopted to analyze the geomorphological evolution of long time series, the accuracy of the 3D scenes of repeated observations may change significantly.…”

Section: Introductionmentioning

confidence: 99%

Studies on Three-Dimensional (3D) Accuracy Optimization and Repeatability of UAV in Complex Pit-Rim Landforms As Assisted by Oblique Imaging and RTK Positioning

Gan

Yuan

et al. 2021

Sensors

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Unmanned Aerial Vehicles (UAVs) are a novel technology for landform investigations, monitoring, as well as evolution analyses of long−term repeated observation. However, impacted by the sophisticated topographic environment, fluctuating terrain and incomplete field observations, significant differences have been found between 3D measurement accuracy and the Digital Surface Model (DSM). In this study, the DJI Phantom 4 RTK UAV was adopted to capture images of complex pit-rim landforms with significant elevation undulations. A repeated observation data acquisition scheme was proposed for a small amount of oblique-view imaging, while an ortho-view observation was conducted. Subsequently, the 3D scenes and DSMs were formed by employing Structure from Motion (SfM) and Multi-View Stereo (MVS) algorithms. Moreover, a comparison and 3D measurement accuracy analysis were conducted based on the internal and external precision by exploiting checkpoint and DSM of Difference (DoD) error analysis methods. As indicated by the results, the 3D scene plane for two imaging types could reach an accuracy of centimeters, whereas the elevation accuracy of the orthophoto dataset alone could only reach the decimeters (0.3049 m). However, only 6.30% of the total image number of oblique images was required to improve the elevation accuracy by one order of magnitude (0.0942 m). (2) An insignificant variation in internal accuracy was reported in oblique imaging-assisted datasets. In particular, SfM-MVS technology exhibited high reproducibility for repeated observations. By changing the number and position of oblique images, the external precision was able to increase effectively, the elevation error distribution was improved to become more concentrated and stable. Accordingly, a repeated observation method only including a few oblique images has been proposed and demonstrated in this study, which could optimize the elevation and improve the accuracy. The research results could provide practical and effective technology reference strategies for geomorphological surveys and repeated observation analyses in sophisticated mountain environments.

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Accuracy Assessment of a Photogrammetric UAV Block by using Different Software and Adopting Diverse Processing Strategies

Cited by 7 publications

References 0 publications

Accuracy Assessment of a UAV Block by Different Software Packages, Processing Schemes and Validation Strategies

Accuracy Assessment of a UAV Block by Different Software Packages, Processing Schemes and Validation Strategies

Geometric and Radiometric Consistency of Parrot Sequoia Multispectral Imagery for Precision Agriculture Applications

Studies on Three-Dimensional (3D) Accuracy Optimization and Repeatability of UAV in Complex Pit-Rim Landforms As Assisted by Oblique Imaging and RTK Positioning

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