• Electronics and Telecommunications Trends
• /
• v.38 no.3
• /
• pp.11-19
• /
• 2023

Drones, which were early operated by remote control, have evolved to enable autonomous flight by combining various sensors and software tools. In particular, autonomous flight of drones was possible since the application of GNSS-RTK (global navigation satellite system with real-time kinematic positioning), a precision satellite navigation technology. For instance, unmanned drone delivery based on GNSS-RTK data was demonstrated for pizza delivery in Korea for the first time in 2021. However, the vulnerabilities of GNSS-RTK should be overcome for delivery drones to be commercialized. In particular, jamming in the navigation system and low positioning accuracy in urban areas should be addressed. Solving these two problems can lead to stable flight, takeoff, and landing of drones in urban areas, and the corresponding solutions are expected to establish a hybrid positioning technology. We discuss current trends in hybrid positioning technology that can either replace or complement GNSS-RTK for stable drone autonomous flight.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.13 no.3
• /
• pp.580-585
• /
• 2009

Real Time Locating Systems (RTLS) are used to track and identify the location of objects in real time using simple, inexpensive tags attached to or embedded in objects and readers that receive the wireless signals from these tags to determine their locations. A tag is powered an internal source such as a battery. The blink frequency of a tag affects the energy efficiency and the locating accuracy of RTLS. The mobility of a tag also affects the locating accuracy. In this paper, we introduce a RTLS tag design which improves the locating accuracy and the power efficiency. We propose an adaptive transmission-rate control algorithm using a motion sensor. By analyzing the signal pattern of the motion sensor, we can build a model to estimate the speed of the motion. Using this model, our algorithm can achieve better locating accuracy and lower power consumption than those of the conventional method. In our experiments, the number of transmission reduced as 40%, keeping similar locating accuracy.

• Journal of Astronomy and Space Sciences
• /
• v.19 no.4
• /
• pp.377-384
• /
• 2002

We have developed Real-time Phase DAta processor(RPDAP) for GPS L1 carrie. And also, we tested the RPDAP's positioning accuracy compared with results of real time kinematic(RTK) positioning. While quality of the conventional L1 RTK positioning highly depend on receiving condition, the RPDAP can gives more stable positioning result because of different set of common GPS satellites, which searched by elevation mask angle and signal strength. In this paper, we demonstrated characteristics of the RPDAP compared with the L1 RTK technique. And we discussed several improvement ways to apply the RPDAP to precise real-time positioning using low-cost GPS receiver. With correcting the discussed weak points in new future, the RPDAP will be used in the field of precise real-time application, such as precise car navigation and precise personal location services.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.20 no.1
• /
• pp.142-152
• /
• 2016

GPS is not able to be used for indoor positioning and currently most of techniques emerging to overcome the limit of GPS utilize private wireless networks. However, these methods require high costs for installation and maintenance, and they are inappropriate to be used in the place where precise positioning is needed as in indoor parking lots. This paper proposes a vehicular indoor positioning method based on QR-code recognition. The method gets an absolute coordinate through QR-code scanning, and obtain the location (an relative coordinate) of a black-box camera using the tilt and roll angle correction through affine transformation, scale transformation, and trigonometric function. Using these information of an absolute coordinate and an relative one, the precise position of a car is estimated. As a result, average error of 13.79cm is achieved and it corresponds to just 27.6% error rate in contrast to 50cm error of the recent technique based on wireless networks.

• Journal of Advanced Marine Engineering and Technology
• /
• v.41 no.4
• /
• pp.353-361
• /
• 2017

As ship-based tourism increases, safe sailing and management are necessary to prevent maritime accidents. Because external rescue support cannot arrive rapidly in the case of ship-related accidents, the initial response is very important for damage minimization. Further, for secondary damage prevention, it is necessary to accurately determine passenger positions. In this paper, considering the characteristics of a ship, the enhanced-Zigbee(e-Zigbee) position determination technology (PDT) is applied, which improved upon the Zigbee PDT by having advantages such as low power consumption and smaller size. According to user needs, a low-cost and high-precision passenger positioning tag and access point(AP) is provided. A ship testbed that yields improved positioning accuracy based on a performance evaluation is constructed.

• Journal of Korean Society for Geospatial Information Science
• /
• v.3 no.2 s.6
• /
• pp.15-28
• /
• 1995

The GPS positioning involves not only 'natural' errors associated with the satellites position errors, refraction of EM wave in the ionosphere, etc., but also 'artificial' errors associated with the operation of S/A (Selective Availability). In this paper, we present the principles, accuracies and applicabilities of our personal DGPS method, which employs the position-correction method on the GPS positionings data collected at the reference and the remote sites. The essential requirement of our DGPS method is that two GPS receivers should utilize the identical Navstar satellites at the same time. The positioning error (1 drms) of the stand-alone GPS is of an order of a few tens meters, while that of horizontal position by our DGPS method is about 1m and that of vertical position is about 2m We applied out DGPS technique in positioning moving objects, and obtained satisfactory results in tracking the trajectories of a car on the road and the those of drifters in the sea.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2009.06a
• /
• pp.597-598
• /
• 2009

• The Journal of the Korea institute of electronic communication sciences
• /
• v.7 no.2
• /
• pp.327-332
• /
• 2012

In this paper, we analyzed the influence of different observation stations distributions on satellite clock offset estimation based on the PANDA software. The result shows that, when the distance between stations is shorter than 200km, the correlation of troposphere parameter and satellite clock offset parameter is strong, the accuracy of satellite clock offset estimation will be up to 0.8ns; when the distance between stations is up to 500km, as the correction of troposphere parameter and satellite clock offset parameter is significantly reduced, and the two kinds of parameters can be distinguished.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.28 no.2
• /
• pp.289-295
• /
• 2010

Yangsan fault system is a large fault more than 170km and one of the important structures Geologically that has been create recently in the Korean Peninsula. Debates have been made incessantly and widely throughout the Yangsan fault system because it's a lot of earthquake record. In this study, GPS data that was received from Yangsan GPS station in were processed by the Precise Point Positioning and the movement velocity was calculated by the statistical process about the results, where is the fault zone. The results showed that Yangsan is moving by azimuth angle of $126^{\circ}$ and the velocity of 49mm/year. It is respected that this results will be utilized in basic data about geophysics.

• Korean Journal of Remote Sensing
• /
• v.37 no.5_1
• /
• pp.1163-1175
• /
• 2021

In autonomous driving, road markings are an essential element for object tracking, path planning and they are able to provide important information for localization. This paper presents an approach to update and measure road surface markers with HD maps as well as matching using inverse perspective mapping. The IPM removes perspective effects from the vehicle's front camera image and remaps them to the 2D domain to create a bird-view region to fit with HD map regions. In addition, letters and arrows such as stop lines, crosswalks, dotted lines, and straight lines are recognized and compared to objects on the HD map to determine whether they are updated. The localization of a newly installed object can be obtained by referring to the measurement value of the surrounding object on the HD map. Therefore, we are able to obtain high accuracy update results with very low computational costs and low-cost cameras and GNSS/INS sensors alone.