Assessing the Geospatial Accuracy of Aerial Imagery Collected with Various UAS Platforms

2018 ◽  
Vol 61 (6) ◽  
pp. 1823-1829 ◽  
Author(s):  
Alysa A. Gauci ◽  
Christian J. Brodbeck ◽  
Aurelie M. Poncet ◽  
Thorsten Knappenberger
Keyword(s):  
Data Processing ◽  
Precision Agriculture ◽  
Unmanned Aircraft ◽  
Aerial Imagery ◽  
Ground Control ◽  
Control Points ◽  
Flight Altitude ◽  
Gps Receivers ◽  
Ground Control Points ◽  
Very High

Abstract. Recent development of small unmanned aircraft systems (UAS) provides a relatively low-cost solution to collect aerial imagery with very high spatial and temporal resolutions. The geospatial accuracy of collected data can range from a few centimeters to several meters, and the use of ground control points (GCPs) is recommended to correct for large geospatial errors. However, whether or not GCPs are used, the true geospatial accuracy of collected UAS data remains unknown. The objective of this study was to measure and compare the geospatial accuracy of images obtained with various UAS platforms at two flight altitudes. Aerial imagery was collected using four platforms equipped with different RGB cameras: Phantom 4, eBee Ag, eBee Plus, and Trimble UX5. All platforms were equipped with manufacturer GPS receivers, and RTK was activated on the eBee Plus. Each platform was flown at 75 and 120 m altitudes, and the experiment was replicated three times. Results demonstrated that using GCPs during data processing improved the horizontal and vertical accuracies of the Phantom 4, eBee Ag, and Trimble UX, decreased the between-flight variability, and accounted for the negative effect of flight altitude. On the other hand, the RTK technology used with the eBee Plus resulted in images with very high geospatial accuracy with or without GCPs. Using GCPs during data processing or RTK technology at the time of flight provided aerial imagery with horizontal accuracies of 1.5 to 10 cm and vertical accuracies of 0.0 to 0.4 m. These results are within an acceptable range for data utilization, unlike the horizontal and vertical accuracies obtained without GCPs or RTK, which ranged from 32 to 441 cm and from 1 to 126 m, respectively. Results from this study quantify the geospatial accuracy of UAS imagery and provide a better understanding of the relationships between the accuracy of the GPS receivers in UAS, flight altitude, and horizontal and vertical accuracies of collected images. Keywords: Accuracy, Drone, Ground control points, Precision agriculture, UAV.

scholarly journals Glacier topography and elevation changes from Pléiades very high resolution stereo images

2014 ◽  
Vol 8 (5) ◽  
pp. 4849-4883 ◽  
Author(s):  
E. Berthier ◽  
C. Vincent ◽  
E. Magnússon ◽  
Á. Þ. Gunnlaugsson ◽  
P. Pitte ◽  
...  
Keyword(s):  
Field Measurements ◽  
Ground Control ◽  
European Alps ◽  
Control Points ◽  
Mass Balances ◽  
Ground Control Points ◽  
Digital Elevation ◽  
Stereo Imagery ◽  
Elevation Changes ◽  
Very High

Abstract. In response to climate change, most glaciers are losing mass and hence contribute to sea-level rise. Repeated and accurate mapping of their surface topography is required to estimate their mass balance and to extrapolate/calibrate sparse field glaciological measurements. In this study we evaluate the potential of Pléiades sub-meter stereo imagery to derive digital elevation models (DEMs) of glaciers and their elevation changes. Our five validation sites are located in Iceland, the European Alps, the Central Andes, Nepal and Antarctica. For all sites, nearly simultaneous field measurements were collected to evaluate the Pléiades DEMs. For Iceland, the Pléiades DEM is also compared to a Lidar DEM. The vertical biases of the Pléiades DEMs are less than 1 m if ground control points (GCPs) are used, but reach up to 6 m without GCPs. Even without GCPs, vertical biases can be reduced to a few decimetres by horizontal and vertical co-registration of the DEMs to reference altimetric data on ice-free terrain. Around these biases, the vertical precision of the Pléiades DEMs is ±1 m and even ±0.5 m on the flat glacier tongues (1-sigma confidence level). We also demonstrate the high potential of Pléiades DEMs for measuring seasonal, annual and multi-annual elevation changes with an accuracy of 1 m or better. The negative glacier-wide mass balances of the Argentière Glacier and Mer de Glace (−1.21 ± 0.16 and −1.19 ± 0.16 m.w.e. yr−1, respectively) are revealed by differencing SPOT5 and Pléiades DEMs acquired in August 2003 and 2012 demonstrating the continuing rapid glacial wastage in the Mont-Blanc area.

Evaluation of 3D Geo-Positioning Based on Bias-Compensated RPCs for Across-Track QuickBird Stereo Imagery

2012 ◽  
Vol 226-228 ◽  
pp. 1958-1964
Author(s):  
Weian Wang ◽  
Shu Ying Xu ◽  
Gang Qiao
Keyword(s):  
Vertical Direction ◽  
Ground Control ◽  
Control Points ◽  
Accuracy Analysis ◽  
Geometric Correction ◽  
Positioning Accuracy ◽  
Ground Control Points ◽  
Order Polynomial ◽  
Stereo Imagery ◽  
Very High

This paper investigates the geo-positioning accuracy of across-track QuickBird stereo imagery in Shanghai, China, where the terrain relief is very low about 3m but with very high buildings up to 380m. The rational function model (RFM) and the bias-compensated RFM with different parameters are employed to do accuracy analysis with different configurations of ground control points (GCPs). The systematic errors in vendor provided RPCs are revealed and discussed. The results of bias-compensated RFM show that different strategies in terms of the number of GCP and different geometric correction methods should be taken into consideration in order for a better and reasonable positioning accuracy in the three directions. The results also show that the best accuracy of 0.6m in horizontal direction and 0.8m in vertical direction can be acquired by the second-order polynomial model when GCPs are more than 8.

scholarly journals A METHOD FOR SIMULTANEOUS AERIAL AND TERRESTRIAL GEODATA ACQUISITION FOR CORRIDOR MAPPING

2015 ◽  
Vol XL-1/W4 ◽  
pp. 227-232 ◽  
Author(s):  
P. Molina ◽  
M. Blázquez ◽  
J. Sastre ◽  
I. Colomina
Keyword(s):  
Spatial Configuration ◽  
Critical Role ◽  
Control Point ◽  
Unmanned Aircraft ◽  
Ground Control ◽  
Control Points ◽  
Post Processing ◽  
Simultaneous Operation ◽  
Ground Control Points ◽  
Sensor Orientation

In this paper, we present mapKITE, a new mobile, simultaneous terrestrial and aerial, geodata collection and post-processing method. On one side, the method combines a terrestrial mobile mapping system (TMMS) with an unmanned aerial mapping one, both equipped with remote sensing payloads (at least, a nadir-looking visible-band camera in the UA) by means of which aerial and terrestrial geodata are acquired simultaneously. This tandem geodata acquisition system is based on a terrestrial vehicle (TV) and on an unmanned aircraft (UA) linked by a 'virtual tether', that is, a mechanism based on the real-time supply of UA waypoints by the TV. By means of the TV-to-UA tether, the UA follows the TV keeping a specific relative TV-to-UA spatial configuration enabling the simultaneous operation of both systems to obtain highly redundant and complementary geodata. <br><br> On the other side, mapKITE presents a novel concept for geodata post-processing favoured by the rich geometrical aspects derived from the mapKITE tandem simultaneous operation. The approach followed for sensor orientation and calibration of the aerial images captured by the UA inherits the principles of Integrated Sensor Orientation (ISO) and adds the pointing-and-scaling photogrammetric measurement of a distinctive element observed in every UA image, which is a coded target mounted on the roof of the TV. By means of the TV navigation system, the orientation of the TV coded target is performed and used in the post-processing UA image orientation approach as a Kinematic Ground Control Point (KGCP). The geometric strength of a mapKITE ISO network is therefore high as it counts with the traditional tie point image measurements, static ground control points, kinematic aerial control and the new point-and-scale measurements of the KGCPs. With such a geometry, reliable system and sensor orientation and calibration and eventual further reduction of the number of traditional ground control points is feasible. <br><br> The different technical concepts, challenges and breakthroughs behind mapKITE are presented in this paper, such as the TV-to-UA virtual tether and the use of KGCP measurements for UA sensor orientation. In addition, the use in mapKITE of new European GNSS signals such as the Galileo E5 AltBOC is discussed. Because of the critical role of GNSS technologies and the potential impact on the corridor mapping market, the European Commission and the European GNSS Agency, in the frame of the European Union Framework Programme for Research and Innovation “Horizon 2020,” have recently awarded the “mapKITE” project to an international consortium of organizations coordinated by GeoNumerics S.L.

scholarly journals mapKITE: A NEW PARADIGM FOR SIMULTANEOUS AERIAL AND TERRESTRIAL GEODATA ACQUISITION AND MAPPING

2016 ◽  
Vol XLI-B1 ◽  
pp. 957-962
Author(s):  
P. Molina ◽  
M. Blázquez ◽  
J. Sastre ◽  
I. Colomina
Keyword(s):  
Real Time ◽  
Unmanned Aircraft ◽  
Ground Control ◽  
Control Points ◽  
The European Union ◽  
New Paradigm ◽  
Integrated Sensor ◽  
Horizon 2020 ◽  
Ground Control Points ◽  
Sensor Orientation

We introduce a new mobile, simultaneous terrestrial and aerial, geodata collection and post-processing method: mapKITE. By combining two mapping technologies such as terrestrial mobile mapping and unmanned aircraft aerial mapping, geodata are simultaneously acquired from air and ground. More in detail, a mapKITE geodata acquisition system consists on an unmanned aircraft and a terrestrial vehicle, which hosts the ground control station. By means of a real-time navigation system on the terrestrial vehicle, real-time waypoints are sent to the aircraft from the ground. By doing so, the aircraft is linked to the terrestrial vehicle through a “virtual tether,” acting as a “mapping kite.” <br><br> In the article, we entail the concept of mapKITE as well as the various technologies and techniques involved, from aircraft guidance and navigation based on IMU and GNSS, optical cameras for mapping and tracking, sensor orientation and calibration, etc. Moreover, we report of a new measurement introduced in mapKITE, that is, point-and-scale photogrammetric measurements [of image coordinates and scale] for optical targets of known size installed on the ground vehicle roof. By means of accurate posteriori trajectory determination of the terrestrial vehicle, mapKITE benefits then from kinematic ground control points which are photogrametrically observed by point-and-scale measures. <br><br> Initial results for simulated configurations show that these measurements added to the usual Integrated Sensor Orientation ones reduce or even eliminate the need of conventional ground control points –therefore, lowering mission costs– and enable selfcalibration of the unmanned aircraft interior orientation parameters in corridor configurations, in contrast to the situation of traditional corridor configurations. <br><br> Finally, we report about current developments of the first mapKITE prototype, developed under the European Union Research and Innovation programme Horizon 2020. The first mapKITE mission will be held at the BCN Drone Center (Collsuspina, Moià, Spain) in mid 2016.

scholarly journals PRECISION ANALYSIS OF POINT-AND-SCALE PHOTOGRAMMETRIC MEASUREMENTS FOR CORRIDOR MAPPING: PRELIMINARY RESULTS

2016 ◽  
Vol XL-3/W4 ◽  
pp. 85-90 ◽  
Author(s):  
P. Molina ◽  
M. Blázquez ◽  
J. Sastre ◽  
I. Colomina
Keyword(s):  
Unmanned Aircraft ◽  
Ground Control ◽  
Control Points ◽  
Post Processing ◽  
Single Pass ◽  
Preliminary Results ◽  
Ground Control Points ◽  
Sensor Orientation ◽  
Calibration Pattern ◽  
Key Aspects

This paper addresses the key aspects of the sensor orientation and calibration approach within the mapKITE concept for corridor mapping, focusing on the contribution analysis of point-and-scale measurements of kinematic ground control points. MapKITE is a new mobile, simultaneous terrestrial and aerial, geodata acquisition and post-processing method. On one hand, the acquisition system is a tandem composed of a terrestrial mobile mapping system and an unmanned aerial system, the latter equipped with a remote sensing payload, and linked through a 'virtual tether', that is, a real-time waypoint supply from the terrestrial vehicle to the unmanned aircraft. On the other hand, mapKITE entails a method for geodata post-processing (specifically, sensor orientation and calibration) based on the described acquisition paradigm, focusing on few key aspects: the particular geometric relationship of a mapKITE network &ndash; the aerial vehicle always observes the terrestrial one as they both move &ndash;, precise air and ground trajectory determination &ndash; the terrestrial vehicle is regarded as a kinematic ground control point &ndash; and new photogrammetric measurements &ndash; pointing on and measuring the scale of an optical target on the roof of the terrestrial vehicle &ndash; are exploited. &lt;br&gt;&lt;br&gt; In this paper, we analyze the performance of aerial image orientation and calibration in mapKITE for corridor mapping, which is the natural application niche of mapKITE, based on the principles and procedures of integrated sensor orientation with the addition of point-and-scale photogrammetric measurements of the kinematic ground control points. To do so, traditional (static ground control points, photogrammetric tie points, aerial control) and new (pointing-and-scaling of kinematic ground control points) measurements have been simulated for mapKITE corridor mapping missions, consisting on takeoff and calibration pattern, single-pass corridor operation potentially performing calibration patterns, and landing and calibration pattern. Our preliminary results show that the exterior orientation, interior orientation and tie points precision estimates are better when using kinematic control with few static ground control, and even with excluding the latter. We conclude then that mapKITE can be a breakthrough on the UAS-based corridor mapping field, as precision requirements can be achieved for single-pass operation with no need for traditional static ground control points.

Development of a 3D Viewer for georeferencing and monoplotting of historical terrestrial images.

2020 ◽  
Author(s):  
Sebastian Flöry ◽  
Camillo Ressl ◽  
Gerhard Puercher ◽  
Norbert Pfeifer ◽  
Markus Hollaus ◽  
...  
Keyword(s):  
Digital Terrain Model ◽  
Local Scale ◽  
Aerial Imagery ◽  
Ground Control ◽  
Control Points ◽  
Mountainous Regions ◽  
Terrain Model ◽  
Digital Terrain ◽  
Ground Control Points ◽  
Selection Of

&lt;p&gt;Mountain regions are disproportionately affected by global warming and changing precipitation conditions. Especially the strong variations within high mountain ranges at the local scale require additional sources in order to quantify changes within this challenging environment. With the emergence of alpine tourism, terrestrial photographs became available by the end of 1800, predating aerial imagery for the selected study areas by 50 years. Due to the earlier availability and oblique acquisition geometry these images are a promising source for quantifying changes within mountainous regions at the local scale. Within the research project SEHAG, methods to process these images and to analyse their potential to quantify and describe environmental changes are developed and applied to study areas in Austria and Italy.&lt;/p&gt;&lt;p&gt;One of the prerequisites for the estimation of changes based on terrestrial imagery is the calculation of the corresponding object point for each pixel in a global coordinate system resulting in a georeferenced orthorectified image. This can be achieved by intersecting the ray defined by the projection center of the camera and each pixel with a digital terrain model, a process known as monoplotting.&lt;/p&gt;&lt;p&gt;So far 1000 terrestrial images with unknown interior and exterior orientation have been collected from various archives for the selected study areas Kaunertal, Horlachtal (both Tyrol, Austria) and Martelltal (South Tyrol, Italy). In order to estimate all camera parameters a 3D viewer for the selection of ground control points has been developed and implemented. The estimation of the exterior and interior orientation is done in OrientAL.&amp;#160;&lt;/p&gt;&lt;p&gt;Preliminary results for selected images show, that especially the developed 3D viewer is an important improvement for the selection of well distributed ground control points and the accurate estimation of the exterior and interior orientation. Monoplotting depends on a digital terrain model, which cannot be computed from the terrestrial images alone due to missing overlap and different acquisitions times. Hence, the combination with historical digital terrain models derived from aerial imagery is necessary to minimize errors introduced due to changes in topography until today. While the large amount of terrestrial images with their oblique acquisition geometries can be exploited to fill occluded areas by combining the results from multiple images, the partly missing or inaccurate temporal information poses another limitation.&lt;/p&gt;&lt;p&gt;With this large image collection, for the first time, we are able to evaluate the use of historical oblique terrestrial photographs for change detection in a systematic manner. This will promote knowledge about challenges, limitations and the achievable accuracy of monoplotting within mountainous regions. The work is part of the SEHAG project (project number I 4062) funded by the Austrian Science Fund (FWF).&lt;/p&gt;

scholarly journals mapKITE: A NEW PARADIGM FOR SIMULTANEOUS AERIAL AND TERRESTRIAL GEODATA ACQUISITION AND MAPPING

2016 ◽  
Vol XLI-B1 ◽  
pp. 957-962 ◽  
Author(s):  
P. Molina ◽  
M. Blázquez ◽  
J. Sastre ◽  
I. Colomina
Keyword(s):  
Real Time ◽  
Unmanned Aircraft ◽  
Ground Control ◽  
Control Points ◽  
The European Union ◽  
New Paradigm ◽  
Integrated Sensor ◽  
Horizon 2020 ◽  
Ground Control Points ◽  
Sensor Orientation

We introduce a new mobile, simultaneous terrestrial and aerial, geodata collection and post-processing method: mapKITE. By combining two mapping technologies such as terrestrial mobile mapping and unmanned aircraft aerial mapping, geodata are simultaneously acquired from air and ground. More in detail, a mapKITE geodata acquisition system consists on an unmanned aircraft and a terrestrial vehicle, which hosts the ground control station. By means of a real-time navigation system on the terrestrial vehicle, real-time waypoints are sent to the aircraft from the ground. By doing so, the aircraft is linked to the terrestrial vehicle through a “virtual tether,” acting as a “mapping kite.” &lt;br&gt;&lt;br&gt; In the article, we entail the concept of mapKITE as well as the various technologies and techniques involved, from aircraft guidance and navigation based on IMU and GNSS, optical cameras for mapping and tracking, sensor orientation and calibration, etc. Moreover, we report of a new measurement introduced in mapKITE, that is, point-and-scale photogrammetric measurements [of image coordinates and scale] for optical targets of known size installed on the ground vehicle roof. By means of accurate posteriori trajectory determination of the terrestrial vehicle, mapKITE benefits then from kinematic ground control points which are photogrametrically observed by point-and-scale measures. &lt;br&gt;&lt;br&gt; Initial results for simulated configurations show that these measurements added to the usual Integrated Sensor Orientation ones reduce or even eliminate the need of conventional ground control points –therefore, lowering mission costs– and enable selfcalibration of the unmanned aircraft interior orientation parameters in corridor configurations, in contrast to the situation of traditional corridor configurations. &lt;br&gt;&lt;br&gt; Finally, we report about current developments of the first mapKITE prototype, developed under the European Union Research and Innovation programme Horizon 2020. The first mapKITE mission will be held at the BCN Drone Center (Collsuspina, Moià, Spain) in mid 2016.

scholarly journals GEOREFERENCING ACCURACY ANALYSIS OF A SINGLE WORLDVIEW-3 IMAGE COLLECTED OVER MILAN

2016 ◽  
Vol XLI-B1 ◽  
pp. 429-434 ◽  
Author(s):  
L. Barazzetti ◽  
F. Roncoroni ◽  
R. Brumana ◽  
M. Previtali
Keyword(s):  
Bias Correction ◽  
Rational Functions ◽  
The Other ◽  
Ground Control ◽  
Control Points ◽  
Accuracy Analysis ◽  
Camera Model ◽  
Ground Control Points ◽  
High Resolution Satellite Imagery ◽  
Very High

The use of rational functions has become a standard for very high-resolution satellite imagery (VHRSI). On the other hand, the overall geolocalization accuracy via direct georeferencing from on board navigation components is much worse than image ground sampling distance (predicted < 3.5 m CE90 for WorldView-3, whereas GSD = 0.31 m for panchromatic images at nadir). <br><br> This paper presents the georeferencing accuracy results obtained from a single WorldView-3 image processed with a bias compensated RPC camera model. Orientation results for an image collected over Milan are illustrated and discussed for both direct and indirect georeferencing strategies as well as different bias correction parameters estimated from a set of ground control points. Results highlight that the use of a correction based on two shift parameters is optimal for the considered dataset.

scholarly journals Corridor Mapping of Sandy Coastal Foredunes with UAS Photogrammetry and Mobile Laser Scanning

2019 ◽  
Vol 11 (11) ◽  
pp. 1352 ◽  
Author(s):  
Alphonse Nahon ◽  
Pere Molina ◽  
Marta Blázquez ◽  
Jennifer Simeon ◽  
Sylvain Capo ◽  
...  
Keyword(s):  
Laser Scanning ◽  
Management Practices ◽  
Control Point ◽  
Unmanned Aircraft ◽  
Ground Control ◽  
Scanning System ◽  
Control Points ◽  
Ground Control Points ◽  
Spatial Coverage ◽  
Mean Square Errors

Recurrent monitoring of sandy beaches and of the dunes behind them is needed to improve the scientific knowledge on their dynamics as well as to develop sustainable management practices of those valuable landforms. Unmanned Aircraft Systems (UAS) are sought as a means to fulfill this need, especially leveraged by photogrammetric and LiDAR-based mapping methods and technology. The present study compares different strategies to carry UAS photogrammetric corridor mapping over linear extensions of sandy shores. In particular, we present results on the coupling of a UAS with a mobile laser scanning system, operating simultaneously in Cap Ferret, SW France. This aerial-terrestrial tandem enables terrain reconstruction with kinematic ground control points, thus largely avoiding the deployment of surveyed ground control points on the non-stable sandy ground. Results show how these three techniques—mobile laser scanning, photogrammetry based on ground control points, and photogrammetry based on kinematic ground control points—deliver accurate (i.e., root mean square errors < 15 cm) 3D reconstruction of beach-to-dune transition areas, the latter being performed at lower survey and logistic costs, and with enhanced spatial coverage capabilities. This study opens the gate for exploring longer (hundreds of kilometers) shoreline dynamics with ground-control-point-free air and ground mapping techniques.

scholarly journals Improving the Accuracy of Aerial Photography Using Ground Control Points

2021 ◽  
Vol 15 (4) ◽  
pp. 42-47
Author(s):  
R. K. Kurbanov ◽  
N. I. Zakharova ◽  
D. M. Gorshkov
Keyword(s):  
Data Processing ◽  
Unmanned Aerial Vehicle ◽  
High Precision ◽  
Aerial Photography ◽  
Ground Control ◽  
Control Points ◽  
Post Processing ◽  
Standard Data ◽  
Ground Control Points ◽  
Aerial Vehicle

The authors showed that it is possible to quickly collect up-to-date information on the agricultural land condition using an unmanned aerial vehicle. It was noted that the use of ground control points increases the accuracy of project measurements, helps to compare the project post-processing results with the real measurements. (Research purpose) To compare the results of standard and high-precision post-processing of aerial survey data using ground control points. (Materials and methods) Aerial photography was carried out on a 1.1- hectare breeding field. The authors used DJI Matrice 200 v2 unmanned aerial vehicle with a GNSS L1/L2 receiver and a modified DJI X4S camera, five control points sized 50 × 50 centimeters and an EMLID Reach RS2 multi-frequency GNSS receiver. The results of scientific research into the use of ground control points during aerial photography were studied. (Results and discussion) It was found out that the error of georeferencing images obtained by an unmanned aerial vehicle without control points is significantly higher during the standard data processing compared to the high-precision one. The project error when using five control points is 3.9 times higher during the standard data processing. (Conclusions) It was shown that using ground control points it is possible to improve the project measurement accuracy, as well as compare the project post-processing results with the measurements on the ground. It was detected that the high-precision monitoring enables the use of fewer ground control points. It was found out that in order to obtain data with the accuracy of 2-4 centimeters in plan and height, at least 3 ground control points need to be used during the high-precision post-processing.

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