The Influence of the Number of Satellites on the Accuracy of RTK GPS Positions

Lemmon, Timothy R.; Gerdan, George P.

doi:10.1080/00050351.1999.10558774

Cited by 14 publications

(5 citation statements)

References 2 publications

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“…Thirty-one ground control targets were spread throughout the scene, in order to provide independent validation of the photogrammetric measurements. Following the methods of [28], we used square targets (45 × 45 cm) for the validation. The ground control was surveyed using dual-frequency differential GPS observations, with coordinate accuracies in the range of 2-4 cm [29].…”

Section: Study Area and Datamentioning

confidence: 99%

“…Figure 3 shows an example image from our study area during the snow-covered flight. The frame images were synched to GPS time using the camera flash to send an event trigger to the GPS receiver, to which the time information was ascribed [28]. The camera was calibrated prior to flight using standard methods.…”

Section: Study Area and Datamentioning

confidence: 99%

“…The second case uses solely the perspective center coordinates (Xo, Yo, Zo) obtained from the UAS navigation solution to constrain the weighted bundle adjustment. This method is similar to the one proposed in [28] and is also known as airborne aerotriangulation or alternatively, direct georeferencing. Because there is a spatial offset between the GPS antenna and the perspective center of the camera, a lever arm offset was measured in the laboratory a priori and then applied post-flight.…”

Section: Photogrammetric Reconstructionmentioning

confidence: 99%

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Snow Depth Retrieval with UAS Using Photogrammetric Techniques

et al. 2015

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Alpine areas pose challenges for many existing remote sensing methods for snow depth retrieval, thus leading to uncertainty in water forecasting and budgeting. Herein, we present the results of a field campaign conducted in Tasmania, Australia in 2013 from which estimates of snow depth were derived using a low-cost photogrammetric approach on-board a micro unmanned aircraft system (UAS). Using commercial off-the-shelf (COTS) sensors mounted on a multi-rotor UAS and photogrammetric image processing techniques, the results demonstrate that snow depth can be accurately retrieved by differencing two surface models corresponding to the snow-free and snow-covered scenes, respectively. In addition to accurate snow depth retrieval, we show that high-resolution (50 cm) spatially continuous snow depth maps can be created using this methodology. Two types of photogrammetric bundle adjustment (BA) routines are implemented in this study to determine the optimal estimates of sensor position and orientation, in addition to 3D scene information; conventional BA (which relies on measured ground control points) and direct BA (which does not require ground control points). Error sources that affect the accuracy of the BA and subsequent snow depth reconstruction are discussed. The results indicate the UAS is capable of providing high-resolution and high-accuracy (<10 cm) estimates of snow depth over a small alpine area OPEN ACCESS Geosciences 2015, 5 265 (~0.7 ha) with significant snow accumulation (depths greater than one meter) at a fraction of the cost of full-size aerial survey approaches. The RMSE of estimated snow depths using the conventional BA approach is 9.6 cm, whereas the direct BA is characterized by larger error, with an RMSE of 18.4 cm. If a simple affine transformation is applied to the point cloud derived from the direct BA, the overall RMSE is reduced to 8.8 cm RMSE.

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Section: Study Area and Datamentioning

confidence: 99%

Section: Study Area and Datamentioning

confidence: 99%

Section: Photogrammetric Reconstructionmentioning

confidence: 99%

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Snow Depth Retrieval with UAS Using Photogrammetric Techniques

et al. 2015

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“…In the DD observations, most of the atmosphere delay can be eliminated considering the short distance between the base station and the rover station [16]. In the past, extensive research on the single GPS RTK was conducted to evaluate its performance in different situations [17][18][19]. The application of single GPS RTK may be extremely limited due to the insufficient number of satellites and the poor configuration of the constellation in hostile environments.…”

Section: Introductionmentioning

confidence: 99%

Estimation of Inter-System Biases between BDS-3/GPS/Galileo and Its Application in RTK Positioning

Zhu

Zhang

2021

Remote Sensing

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For the development of a global navigation satellite system (GNSS), the third generation of BeiDou Navigation Satellite System (BDS-3) achieved full constellation for worldwide service on 23 June 2020. The new signals, B1C and B2a of BDS-3, further enhance the compatibility and interoperability between different GNSSs. In this study, we first assessed the quality of all the signals in BDS-3/GPS/Galileo. Then, to achieve the interoperability among BDS-3/GPS/Galileo, the inter-system bias (ISB), which appears if an inter-system difference exists between two GNSSs, was estimated at overlapping frequencies. Finally, we used the estimated ISBs in real-time kinematic (RTK) positioning. The results show the higher quality of the overlapping frequency B2a/L5/E5a than B1C/L1/E1 in terms of pseudo range multipath. The ISBs are stable both in the short term for one day and in the long term for over a year, which fit a zero-mean normal distribution well when the identical type of receiver is applied. Thus, it is reasonable to ignore the ISBs in the inter-system differences. With the estimated ISBs, the inter-system double-difference RTK can be achieved, which is called a tightly combined model (TCM) RTK. Compared with the traditional intra-system double-difference RTK, which is called a loosely combined model (LCM) RTK, the TCM RTK can achieve a higher success rate (SR) in terms of ambiguity resolution and higher positioning accuracy. In addition, the higher the cutoff elevation angle set, the greater the promotion can be obtained in SR. Even with a cutoff elevation angle of 50°, the SR of TCM is over 80%. Thus, it is important to apply TCM RTK when the observation conditions are limited, such as in dense jungles or the urban canyons.

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“…The Real Time Kinematic (RTK) approach is a differential positioning technique that uses known coordinates of a reference station occupied by one receiver to determine coordinates of unknown points visited by a rover receiver [1]. Similar to static GPS the reference station is set on a point of known coordinates but the use of a data link, to transfer measurements acquired at the reference receiver to the roving receiver, permits the calculation of the rover coordinates at the time of measurement [2]. Details on RTK ambiguity resolution, data transmission and operational considerations can be found in [1].…”

Section: Introductionmentioning

confidence: 99%

Alternative Solutions for RTK-GPS Applications in Building and Road Constructions

Khalil¹

2015

OJCE

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Currently, Global Positioning System (GPS) techniques are becoming a much larger part of the surveying industry. Many companies are now using GPS in their everyday work activities. The Real Time Kinematic (RTK) positioning is an integral part of topographic surveys, road surveying, constructions and most civil engineering applications. Normally, RTK can be used to collect the positioning data successfully and quickly. The civil and construction projects are designed in ground distances while RTK measurements are done in grid coordinate system, in which the distances between points are different from ground. The RTK measurements should be converted to ground for compatibility with the designed. In this paper, the accuracy of three alternatives for converting RTK measurements to ground was studied. These alternatives are, using scale factor, using two ground reference points and using Low Distortion Projection (LDP) surface. For the accuracy investigation purpose, a traverse of 14 points elongated for a distance of about 1400 m was constructed. Its coordinates were measured using total station, then the misclosure error was computed and the coordinates were adjusted. The traverse points coordinates were measured again using RTK_GPS considering one of them as base point. The three studied alternatives were applied and the results were compared. The results show that the accuracy of the three alternatives is ranging from 2.1 to 2.9 cm in the relative position of points to the base point. For absolute position accuracy, the two ground reference points alternative is the most accurate alternative with an average error of 3.8 cm while the other two alternatives are almost the same with an average error of 12.3 cm.

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The Influence of the Number of Satellites on the Accuracy of RTK GPS Positions

Cited by 14 publications

References 2 publications

Snow Depth Retrieval with UAS Using Photogrammetric Techniques

Snow Depth Retrieval with UAS Using Photogrammetric Techniques

Estimation of Inter-System Biases between BDS-3/GPS/Galileo and Its Application in RTK Positioning

Alternative Solutions for RTK-GPS Applications in Building and Road Constructions

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