scholarly journals QUALITY ASSESSMENT OF UAV PHOTOGRAMMETRIC ARCHAEOLOGICAL SURVEY

2019 ◽  
Vol XLII-2/W9 ◽  
pp. 93-100 ◽  
Author(s):  
S. Barba ◽  
M. Barbarella ◽  
A. Di Benedetto ◽  
M. Fiani ◽  
M. Limongiello
Keyword(s):  
3D Model ◽  
Archaeological Site ◽  
Satellite System ◽  
Survey Method ◽  
Archaeological Survey ◽  
Ground Control Points ◽  
Global Positioning ◽  
Aerial Vehicle ◽  
Projection Error ◽  
Oblique Images

<p><strong>Abstract.</strong> The paper reports the results of a photogrammetric survey made using an Unmanned Aerial Vehicle (UAV) in the archaeological site of the Roman Amphitheatre in Avella (Avellino, Italy). The aim of the study is to verify which modality of image acquisition (if only nadiral images or nadiral plus Oblique images), together with the method of Global Positioning Satellite System (GNSS) survey of the Ground Control Points (GCP) is able to produce the better 3D model, in terms of accuracy, in order to extract traditional graphic drawings (plan, elevation and section), suited to the required representation scales (1<span class="thinspace"></span>:<span class="thinspace"></span>100 and 1<span class="thinspace"></span>:<span class="thinspace"></span>50). The accuracy in georeferencing was evaluated analysing the residues on the GCPs; subsequently, a more detailed analysis of the accuracy of the final 3D model was performed analysing the residuals on the image coordinates, also called re-projection error. The method developed is based on the statistical analysis of the different models, built changing the GCPs survey method and the photogrammetric shots acquired. The results of our analysis show that the photogrammetric survey is more ‘stable’ using only nadiral images and that the nRTK technique allows results comparable to those obtained with static measurements, both in precision and in reliability. Moreover, if the GCPs are measured in nRTK mode, taking into consideration the graphical error, the maximum representation scale is 1<span class="thinspace"></span>:<span class="thinspace"></span>100, whereas the use of static technique makes it possible to describe major details, at a scale of 1<span class="thinspace"></span>:<span class="thinspace"></span>50.</p>

scholarly journals Photogrammetric 3D Model via Smartphone GNSS Sensor: Workflow, Error Estimate, and Best Practices

2020 ◽  
Vol 12 (21) ◽  
pp. 3616
Author(s):  
Stefano Tavani ◽  
Antonio Pignalosa ◽  
Amerigo Corradetti ◽  
Marco Mercuri ◽  
Luca Smeraglia ◽  
...  
Keyword(s):  
3D Model ◽  
Model Building ◽  
Satellite System ◽  
Test Case ◽  
Digital Terrain ◽  
Ground Control Points ◽  
Terrain Models ◽  
Aerial Vehicle ◽  
Global Navigation Satellite ◽  
The Impact

Geotagged smartphone photos can be employed to build digital terrain models using structure from motion-multiview stereo (SfM-MVS) photogrammetry. Accelerometer, magnetometer, and gyroscope sensors integrated within consumer-grade smartphones can be used to record the orientation of images, which can be combined with location information provided by inbuilt global navigation satellite system (GNSS) sensors to geo-register the SfM-MVS model. The accuracy of these sensors is, however, highly variable. In this work, we use a 200 m-wide natural rocky cliff as a test case to evaluate the impact of consumer-grade smartphone GNSS sensor accuracy on the registration of SfM-MVS models. We built a high-resolution 3D model of the cliff, using an unmanned aerial vehicle (UAV) for image acquisition and ground control points (GCPs) located using a differential GNSS survey for georeferencing. This 3D model provides the benchmark against which terrestrial SfM-MVS photogrammetry models, built using smartphone images and registered using built-in accelerometer/gyroscope and GNSS sensors, are compared. Results show that satisfactory post-processing registrations of the smartphone models can be attained, requiring: (1) wide acquisition areas (scaling with GNSS error) and (2) the progressive removal of misaligned images, via an iterative process of model building and error estimation.

scholarly journals Unmanned Aerial Vehicle Surveying For Monitoring Road Construction Earthworks

2019 ◽  
Vol 14 (1) ◽  
pp. 1-17 ◽  
Author(s):  
Kalev Julge ◽  
Artu Ellmann ◽  
Romet Köök
Keyword(s):  
Unmanned Aerial Vehicle ◽  
Road Construction ◽  
Point Clouds ◽  
Satellite System ◽  
Ground Control Points ◽  
Surface Models ◽  
Aerial Vehicle ◽  
Global Navigation Satellite ◽  
Sand And Gravel ◽  
The Impact

Unmanned aerial vehicle photogrammetry is a surveying technique that enables generating point clouds, 3D surface models and orthophoto mosaics. These are based on photos captured with a camera placed on an unmanned aerial vehicle. Within the framework of this research, unmanned aerial vehicle photogrammetry surveys were carried out over a sand and gravel embankment with the aim of assessing the vertical accuracy of the derived surface models. Flight altitudes, ground control points and cameras were varied, and the impact of various factors on the results was monitored. In addition, the traditional real-time-kinematic Global Navigation Satellite System surveys were conducted for verifications. Surface models acquired by different methods were used to calculate volumes and compare the results with requirements set by Estonian Road Administration. It was found that with proper measuring techniques an accuracy of 5.7 cm for the heights were achieved.

3D Model By Using Oblique Images From Unmanned Aerial Vehicle (UAV)

2019 ◽  
Author(s):  
Heng Joe Eu ◽  
Muhammad Syahrul Izmeer Abdul Razak ◽  
Norhadija Darwin ◽  
Zulkepli Majid ◽  
Mohd Farid Mohd Ariff ◽  
...  
Keyword(s):  
Unmanned Aerial Vehicle ◽  
3D Model ◽  
Aerial Vehicle ◽  
Oblique Images

scholarly journals Evaluation of the Georeferencing Accuracy of a Photogrammetric Model Using a Quadrocopter with Onboard GNSS RTK

Sensors ◽  
2020 ◽  
Vol 20 (8) ◽  
pp. 2318 ◽  
Author(s):  
Martin Štroner ◽  
Rudolf Urban ◽  
Tomáš Reindl ◽  
Jan Seidl ◽  
Josef Brouček
Keyword(s):  
Vertical Component ◽  
Satellite System ◽  
Bundle Adjustment ◽  
Ground Control ◽  
Control Points ◽  
Ground Sample ◽  
Ground Control Points ◽  
Aerial Vehicle ◽  
Global Navigation Satellite ◽  
Orientation Parameters

Using a GNSS RTK (Global Navigation Satellite System Real Time Kinematic) -equipped unmanned aerial vehicle (UAV) could greatly simplify the construction of highly accurate digital models through SfM (Structure from Motion) photogrammetry, possibly even avoiding the need for ground control points (GCPs). As previous studies on this topic were mostly performed using fixed-wing UAVs, this study aimed to investigate the results achievable by a quadrocopter (DJI Phantom 4 RTK). Three image acquisition flights were performed for two sites of a different character (urban and rural) along with three calculation variants for each flight: georeferencing using ground-surveyed GCPs only, onboard GNSS RTK only, and a combination thereof. The combined and GNSS RTK methods provided the best results (at the expected level of accuracy of 1–2 GSD (Ground Sample Distance)) for both the vertical and horizontal components. The horizontal positioning was also accurate when georeferencing directly based on the onboard GNSS RTK; the vertical component, however, can be (especially where the terrain is difficult for SfM evaluation) burdened with relatively high systematic errors. This problem was caused by the incorrect identification of the interior orientation parameters calculated, as is customary for non-metric cameras, together with bundle adjustment. This problem could be resolved by using a small number of GCPs (at least one) or quality camera pre-calibration.

scholarly journals ARE MEASURED GROUND CONTROL POINTS STILL REQUIRED IN UAV BASED LARGE SCALE MAPPING? ASSESSING THE POSITIONAL ACCURACY OF AN RTK MULTI-ROTOR PLATFORM

2020 ◽  
Vol XLIII-B1-2020 ◽  
pp. 507-514 ◽  
Author(s):  
L. Teppati Losè ◽  
F. Chiabrando ◽  
F. Giulio Tonolo
Keyword(s):  
Large Scale ◽  
Control Point ◽  
Satellite System ◽  
Added Value ◽  
Ground Control ◽  
Positional Accuracy ◽  
Ground Control Points ◽  
Aerial Vehicle ◽  
Global Navigation Satellite ◽  
The Impact

Abstract. The estimate of External Orientation (E.O.) parameters for a block of images is a crucial step in the photogrammetric pipeline and the most demanding in terms of required time and human effort, both during the fieldwork and post-processing phases. Different researchers developed strategies to minimize the impact of this phase. Despite the achievement of good results, it was not possible until now to completely cancel the effect of this step. However, the efforts of the researchers in these years have also been devoted to the implementation of direct photogrammetry strategies, in order to almost completely automate the E.O. of the photogrammetric block. These new approaches were made possible also thanks to the latest developments of commercial UAVs, especially in terms of the installed GPS/GNSS (Global Positioning System/Global Navigation Satellite System) hardware. The aim of this manuscript is to evaluate the different perspectives and issues connected with the deployment of a UAV (Unmanned Aerial Vehicle) equipped with a multi-frequency GPS/GNSS receiver. Starting from the considerations mentioned above and leveraging previous works based on a fixed-wing platform, the focus of this contribution is the assessment of the real performances of an RTK multi-rotor platform addressing several questions. Is it possible to generate added-value products with centimetre 3D accuracies without measuring any ground control point? Which are the operational requirements to be taken into account in the planning phase? Are consolidated UAV mapping operational workflows already available to enable a robust direct georeferencing approach?

scholarly journals Accuracy Assessment of 3D Photogrammetric Models from an Unmanned Aerial Vehicle

Drones ◽  
2019 ◽  
Vol 3 (4) ◽  
pp. 79 ◽  
Author(s):  
Salvatore Barba ◽  
Maurizio Barbarella ◽  
Alessandro Di Benedetto ◽  
Margherita Fiani ◽  
Lucas Gujski ◽  
...  
Keyword(s):  
Unmanned Aerial Vehicle ◽  
Accuracy Assessment ◽  
Archaeological Site ◽  
Test Case ◽  
Accuracy Rate ◽  
Entire Area ◽  
Final Model ◽  
Ground Control Points ◽  
Aerial Vehicle ◽  
Definition Of

The unmanned aerial vehicle (UAV) photogrammetric survey of an archaeological site has proved itself to be particularly efficient. In order to obtain highly accurate and reliable results, it is necessary to design carefully the flight plan and the geo-referencing, while also evaluating the indicators of the accuracy rate. Using as a test case a UAV photogrammetric survey conducted on the archaeological site of the Roman Amphitheatre of Avella (Italy), in this paper, we propose a pipeline to assess the accuracy of the results according to some quality indicators. The flight configuration and the georeferencing chosen is then be checked via the residuals on the ground control points (GCPs), evenly distributed on the edges and over the entire area. With the aim of appraising the accuracy of the final model, we will suggest a method for the outlier detection, taking into account the statistical distribution (both global and of portion of the study object) of the reprojection errors. A filter to reduce the noise within the model will then be implemented through the detection of the angle formed by homologous rays, in order to reach a compromise between the number of the usable points and the reduction of the noise linked to the definition of the 3D model.

scholarly journals EVALUATION OF CAMERA POSITIONS AND GROUND POINTS QUALITY IN A GNSS-NRTK BASED UAV SURVEY: PRELIMINARY RESULTS FROM A PRACTICAL TEST IN MORPHOLOGICAL VERY COMPLEX AREAS

2019 ◽  
Vol XLII-2/W13 ◽  
pp. 637-641 ◽  
Author(s):  
E. Tufarolo ◽  
C. Vanneschi ◽  
M. Casella ◽  
R. Salvini
Keyword(s):  
Real Time ◽  
Satellite System ◽  
Open Pit ◽  
Complex Environments ◽  
Ground Control Points ◽  
Position Detection ◽  
Real Time Kinematic ◽  
Aerial Vehicle ◽  
Camera Position ◽  
Global Navigation Satellite

<p><strong>Abstract.</strong> Open pit mines localized in high mountains are probably one of the most complex environments for Structure-From-Motion (SfM) based photogrammetry. The case study presented in this paper refers to the realization of a detailed topographic mapping in the Torano marble basin (Apuan Alps, Italy) which needed, after decades of excavation activity, a new topographic survey.</p><p>Given the requested very high resolution, the time constraints and safety-related problems, a photogrammetric approach by a fixedwing Unmanned Aerial Vehicle (UAV) was chosen to carry out thesurvey of the basin. In addition, given the morphological complexity of the area, characterized by extreme steep slopes more than hundreds of meters high, and the necessity to minimize the fieldwork without sacrificing the work quality, an UAV equipped with a L1/L2 Network Real Time Kinematic (NRTK) Global Navigation Satellite System (GNSS) was used.</p><p>The scope of this work is to compare the accuracy of UAV derived 3D photogrammetric models realized with different approaches: by using traditional Ground Control Points (GCPs), by using the on-board Network Real Time Kinematic system for camera position detection, and a mix of both. At the end, we tested the quality of the models to verify the reachable levels of accuracy.</p>

scholarly journals An Image-Based Real-Time Georeferencing Scheme for a UAV Based on a New Angular Parametrization

2020 ◽  
Vol 12 (19) ◽  
pp. 3185
Author(s):  
Ehsan Khoramshahi ◽  
Raquel A. Oliveira ◽  
Niko Koivumäki ◽  
Eija Honkavaara
Keyword(s):  
Real Time ◽  
Satellite System ◽  
Local Networks ◽  
Ground Control Points ◽  
Localization And Mapping ◽  
Monocular Slam ◽  
Aerial Vehicle ◽  
Gimbal Lock ◽  
Global Navigation Satellite ◽  
Pyramid Matching

Simultaneous localization and mapping (SLAM) of a monocular projective camera installed on an unmanned aerial vehicle (UAV) is a challenging task in photogrammetry, computer vision, and robotics. This paper presents a novel real-time monocular SLAM solution for UAV applications. It is based on two steps: consecutive construction of the UAV path, and adjacent strip connection. Consecutive construction rapidly estimates the UAV path by sequentially connecting incoming images to a network of connected images. A multilevel pyramid matching is proposed for this step that contains a sub-window matching using high-resolution images. The sub-window matching increases the frequency of tie points by propagating locations of matched sub-windows that leads to a list of high-frequency tie points while keeping the execution time relatively low. A sparse bundle block adjustment (BBA) is employed to optimize the initial path by considering nuisance parameters. System calibration parameters with respect to global navigation satellite system (GNSS) and inertial navigation system (INS) are optionally considered in the BBA model for direct georeferencing. Ground control points and checkpoints are optionally included in the model for georeferencing and quality control. Adjacent strip connection is enabled by an overlap analysis to further improve connectivity of local networks. A novel angular parametrization based on spherical rotation coordinate system is presented to address the gimbal lock singularity of BBA. Our results suggest that the proposed scheme is a precise real-time monocular SLAM solution for a UAV.

scholarly journals 3D MODEL GENERATION USING OBLIQUE IMAGES ACQUIRED BY UAV

2017 ◽  
Vol XLII-4/W2 ◽  
pp. 107-115 ◽  
Author(s):  
A. Lingua ◽  
F. Noardo ◽  
A. Spanò ◽  
S. Sanna ◽  
F. Matrone
Keyword(s):  
Open Source ◽  
Open Source Software ◽  
Low Cost ◽  
Flight Planning ◽  
North West ◽  
Ground Control Points ◽  
Critical Issues ◽  
Aerial Vehicle ◽  
High Level ◽  
Oblique Images

In recent years, many studies revealed the advantages of using airborne oblique images for obtaining improved 3D city models (including façades and building footprints). Here the acquisition and use of oblique images from a low cost and open source Unmanned Aerial Vehicle (UAV) for the 3D high-level-of-detail reconstruction of historical architectures is evaluated. The critical issues of such acquisitions (flight planning strategies, ground control points distribution, etc.) are described. Several problems should be considered in the flight planning: best approach to cover the whole object with the minimum time of flight; visibility of vertical structures; occlusions due to the context; acquisition of all the parts of the objects (the closest and the farthest) with similar resolution; suitable camera inclination, and so on. In this paper a solution is proposed in order to acquire oblique images with one only flight. The data processing was realized using Structure-from-Motion-based approach for point cloud generation using dense image-matching algorithms implemented in an open source software. The achieved results are analysed considering some check points and some reference LiDAR data. The system was tested for surveying a historical architectonical complex: the “Sacro Mo nte di Varallo Sesia” in north-west of Italy. This study demonstrates that the use of oblique images acquired from a low cost UAV system and processed through an open source software is an effective methodology to survey cultural heritage, characterized by limited accessibility, need for detail and rapidity of the acquisition phase, and often reduced budgets.

scholarly journals UNMANNED AERIAL VEHICLE PHOTOGRAMMETRY AND 3D MODELING APPLIED TO VIRTUAL RECONSTRUCTION OF AN ARCHAEOLOGICAL SITE IN THE BRONCE AGE

2019 ◽  
Vol XLII-2/W15 ◽  
pp. 279-284
Author(s):  
F. Carvajal-Ramírez ◽  
A. D. Navarro-Ortega ◽  
F. Agüera-Vega ◽  
P. Martínez-Carricondo
Keyword(s):  
Bronze Age ◽  
Total Error ◽  
Archaeological Site ◽  
Digital Cameras ◽  
Ground Control Points ◽  
Digital Elevation ◽  
Virtual Reconstruction ◽  
Aerial Vehicle ◽  
Augmented Reality Technology ◽  
Elevation Model

<p><strong>Abstract.</strong> The risk of disappearing of cultural heritage of archaeological sites is directly related to the protection level by the corresponding administrations. This is the case of Cortijo Nuevo, an archaeological site with no known precedents in the Iberian Peninsula in the Bronze Age.</p> <p>The recent development of Unmanned Aerial Vehicles (UAV) used as platform carrying digital cameras, let to adapt the well-known classical Photogrammetry technique, in conjunction with Structure from Motion (SfM) and Multi View Stereo (MVS) algorithms, for very high accurate surveying of the terrain.</p> <p>In this work, several digital cartographic products including point cloud, Digital Elevation Model (DEM) and orthoimage were obtained from UAV-Photogrammetric flight with the purpose of document and virtual reconstruction of a damaged archaeological site. All the technical prescriptions of the flight and photogrammetric project were designed for accurately representing the state of the terrain in both epochs, current and previous to damage. The quality control for quantify planimetric and altimetric errors, based on 33 ground control points, showed RMSE<sub>xy</sub>&amp;thinsp;=&amp;thinsp;0.0246&amp;thinsp;m, RMSE<sub>z</sub>&amp;thinsp;=&amp;thinsp;0.0262&amp;thinsp;m and the total error sum of 0.0359&amp;thinsp;m. An integration of virtual 3D archaeological structures with the obtained terrain models was carried out through augmented reality technology, based on the information obtained in this work.</p>

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