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Since the fall of 2003 the Louisiana Aerospace Catalyst Experiences for Students (LaACES) program has been providing university students a two semester project that culminates with the flight of a scientific balloon experiment. During the first semester students complete the Student Ballooning Course (SBC) which teaches basic skills necessary to develop a working scientific payload. The SBC consists of a series of lectures and activities providing instruction in electronics, programming, project management, balloon payload design, and introductory circuit assembly. The SBC introduces the BalloonSat, a sub-assembly designed at LSU for LaACES which contains a microcontroller, real-time clock and a four channel analog-to-digital converter. The second semester is spent on the design, development, testing and calibration of the payloads. Upon completion of the Flight Readiness Review, students travel to the NASA Columbia Scientific Balloon Facility (CSBF) in Palestine, Texas for integration, launch, recovery and science presentations. A flight capable Automatic Packet Reporting System (APRS) radio beacon armed with GPS and command capable cut down was developed to track the balloon during flight and to cut-down the payloads. Tracking vehicles are outfitted with radios tuned to APRS frequency and laptops displaying maps of the payload location. Here we describe LaACES; program development, tools and technologies, implementation, program, management issues and flight experiences.

The article presents a hardware implementation of an APRS (Automatic Packet Reporting System) based tracker for determining the location of an object in real time. It was developed and tested in the educational process at the Faculty of Physics and Engineering Technologies of University of Plovdiv “Paisii Hilendarski”. Students acquire lasting knowledge and develop skills for working with APRS trackers connected between GPS and radio stations that transmit data in the global APRS network. Combining modern microcontrollers with appropriate software and APRS technology, a device with many current applications is obtained.

Smart farms and IoT (Internet of Things) have an inseparable relationship. Sensors, gateways, servers, databases, web-based applications, are all widely used by connected smart farms. Also, the range of communication availability, the amount of power required for communication, and required equipment are differs depending on the networking technology. Hence, the decision of networking technology is very important when implementing a smart farm. While there are many networking technologies, LoRa (Long Range) is one of the most common Low Power Wide Area Network (LPWAN) in use by smart farms in the United States. Theoretically, APRS (Automatic Packet Reporting System) can communicate at greater distances than LoRa. Therefore, the study compares the feasibility of LoRa and APRS in smart farms by measuring the distance coverage of the two networking technologies. All three tests were conducted at the Purdue Agronomy Center for Research and Education where the transmitting antennas were mobile that moved via cars, and the receiving antennas were installed at the same tower. The distances were calculated by using Google Maps, where all the locations for the transmitting points were saved. From evaluating the test results, this paper concludes that LoRa is a more feasible wireless connection than APRS in the smart farm IoT system.

Automatic packet reporting system (APRS) is selected as a candidate for automatic dependent surveillance-broadcast (ADS-B) like solution for unmanned aircraft system traffic management (UTM). The APRS on-board unit (OBU) at 0.5 W radio power and a proper ground transceiver station (GTS) deployment together makes up the infrastructure for unmanned aerial vehicle (UAV) surveillance. The airborne APRS OBU, designed and built using an available LightAPRS module, and the GTS to relay received data into the UTM Cloud is developed in this study. By system integration, the APRS OBU reports position data and flight data periodically to UTM Cloud. This paper presents the development of the ADS-B like operation for UTM using APRS. To avoid communication jamming by HAMs, the adopted APRS shifts its carrying frequency from 144.64 MHz to 144.61 MHz. In addition, the data period is tuned to around 10 s to test its functional capability. The APRS OBU downlinks 90 bytes of surveillance data onto the UTM cloud using the Internet, including position and flight data from Pixhawk flight controller (FC). A series of system performance verifications are conducted to examine APRS ADS-B like reliability and continuity with coverage limit. Through 19 flight tests, the GTS collected 1330 packets of data out of 1331 transmitted from the APRS OBU. Each data packet has the complete 90 bytes for surveillance with position and six degree-of-freedom (DoF) flight data on the UTM cloud. The APRS GTS deployment, with a low rate of missing data, covers a 40 km radius at the specific frequency of 144.61 MHz. The test results verify the functional capability of APRS to support an ADS-B like for UTM in Taiwan.

A design and implementation of an Emergency Message Beacon System (EMBS) using the Automatic Position Reporting System (APRS) protocol is presented in this paper. The EMBS benefits from widely distributed radio network where modern wireless network infrastructure is unavailable such as on open seas or in the middle of jungle. The main concept of the design is that the system an immediate beacon containing current location is transmitted when activates the unit and automatically sends interval beacons to report location, system status, and an instant message. The unit works with either an existing or impromptu APRS ad-hoc networks. The system is designed to transmit low RF power and expected a minimum coverage of at least two kilometers in radius, which is the worst situation case of Line of Sight (LOS) communication. The experimental result shows that the unit can establish radio connection to another station at a range of 2.1 kms. Link budget analysis is theoretically validated the communication.

LAPAN-A2 Satellite, also known as LAPAN-ORARI, is the second satellite developed by the Indonesian National Institute of Aeronautics and Space (LAPAN), especially by Satellite Technology Center. This satellite was launched in 2015, where one of the missions is to support disaster mitigation through the Automatic Packet Reporting System (APRS). The APRS is a method of transmitting messages, status, and positions - using specially formatted AX.25 packets messages. The critical part of the APRS infrastructure is Digital Repeater (digipeater) and Internet Gateways (iGates). The digipeater is usually used to retransmit data packets for extending coverage. The APRS digipeater of LAPAN-A2 is on 145.825 MHz. The iGate is a type of gateway APRS station that functions to collect packages from the radio and feeds them into a worldwide data streams on the internet. This paper describes the design and implementation of SatGate /iGate YF1ZQA for APRS on the LAPAN-A2 Satellite.

Weather and air quality observation recently gained more public awareness. Recent advances in wireless sensor network technologies are fueled by latest advances in microcontrollers and radio transceivers. Efforts have been made to create low-cost open sourced environmental sensor stations and Internet of Things provide open standard protocol that can easily be integrated with various legacy open source systems. This paper proposes the usage of open standard wireless telemetry network based on Automatic Packet Reporting System (APRS) and Messaging Queue Telemetry Transport (MQTT). Integration of an IoT platform with legacy telemetry network is demonstrated and preliminary results show that the integrated platform solution is easy to implement.

Malang Southern Coast is one of the areas highly potential in earthquake and tsunami. An effective mitigation system is needed to manage them. Dual Mitigation System is a system combining Indonesia Tsunami Early Warning System (INA-TEWS) and Automatic Packet Reporting System (APRS). INA-TEWS is a warning system when the earthquake or tsunami takes place. APRS is a radio system to share information digitally. Radio wave can work in emergency situation. The methodology used is by analyzing earthquake data as a foundation of location determination to Dual Mitigation application system. The location of Dual Mitigation System was tested by evacuation process speed and information of APRS. The results show that this system is an effective early warning system employing INA-TEWS data and it gives evacuation process in about 4-6 minutes and 7-10 minutes faster using vehicle and without vehicle by APRS compared to the existing conventional method.

The hierarchical unmanned aerial systems (UAS) traffic management (UTM) is proposed for UAS operation in Taiwan. The proposed UTM is constructed using the similar concept of ATM from the transport category aviation system. Based on the airspace being divided by 400 feet of altitude, the RUTM (regional UTM) is managed by the local government and the NUTM (national UTM) by the Civil Aeronautical Administration (CAA). Under construction of the UTM system infrastructure, this trial tests examine the effectiveness of UAV surveillance under 400 feet using automatic dependent surveillance-broadcast (ADS-B)-like on-board units (OBU). The ground transceiver station (GTS) is designed with the adoptable systems. In these implementation tests, five long-range wide area network (LoRa) gateways and one automatic packet reporting system (APRS) I-Gate are deployed to cover the Tainan Metropolitan area. The data rates are set in different systems from 8 to 12 s to prevent from data conflict or congestion. The signal coverage, time delay, data distribution, and data variance in communication are recorded and analyzed for RUTM operation. Data streaming and Internet manipulation are verified with cloud system stability and availability. Simple operational procedures are defined with priority for detect and avoid (DAA) for unmanned aerial vehicles (UAVs). Mobile communication and Zello broadcasts are introduced and applied to establish controller-to-pilot communication (CPC) for DAA. The UAV flight tests are generally beyond visual line-of-sight (BVLOS) near suburban areas with flight distances to 8 km. On the GTS deployment, six test locations examine communication coverage and effectiveness using ADS-B like OBUs. In system verification, the proposed ADS-B like OBU works well in the UTM infrastructure. The system feasibility is proven with support of receiving data analysis and transceiver efficiency. The trial test supports RUTM in Taiwan for UAV operations.

High altitude balloons (HABs) are typically tracked via GPS data sent via real-time radio-based communication systems such as the Automated Packet Reporting System (APRS). Prefabricated APRS-compatible tracker modules have made it trivial to transmit GPS coordinates and payload parameters in compliance with the requisite AX.25 protocol. However, in order to receive and track APRS signals, conventional methodologies call for the use of a Very High Frequency (VHF) receiver to demodulate signals transmitted on the 440/144 MHz APRS frequencies, along with a compatible antenna and custom methodology for visualizing the HAB's location on a map. The entire assembly is typically costly, cumbersome, and may require an internet connection in order to obtain real-time visualization of the HAB's location. This paper describes a low-cost, handheld system based on open-source software that operates independently of an internet connection. The miniaturized system is suited to tracking done either from a vehicle or on foot, and is cost-effective enough to be within the means of nearly any HAB user. The paper also discusses preliminary test results and further applications., Comment: 12 pages, 6 figures

AX.25 protocol is the most widely used protocol in amateur packet radio network. It has existed for over 30 years and still exist today in a form of Automatic Packet Reporting System (APRS). APRS is widely used for exchanging real-time information in a shared RF environment. Conventional APRS is built on top of Bell 202 modem that is simple to implement but very inefficient regarding use of spectrum and transmitted power. LoRa modulation scheme can be implemented to extend APRS network to include LoRa based network for power constrained applications. This paper proposes using LoRa as a modem choice for APRS and the implementation of a KISS TNC based on LoRa. The prototype LoRa KISS TNC is operational and can be easily integrated with the existing APRS Internet Service network infrastructure.

In many cases in Indonesia, big disasters destroy information and communication system causing delay in emergency response. Rapid assessment for data inventory and field situation recording and reporting, is needed to assist evacuation process and aid distribution. For that purpose, a system called RAPID TIMEER is developed and designed to work in emergency situation where there is no power supply and communication network. This system consists of server and client components. Server, a web based application has a function to send instructions, basic data sets i.e. area/point of interest, maps, contacts, forms for client and receive field data observation from client. On the other hand, the client component, a mobile application based on Android platform and compatible with smartphone, has a main function to record data based on the templates that have been given and send back the results to server. For data communication, this system use independent media such as radio links, wireless sensor network, mobile base transceiver station, automatic packet reporting system. This system can transmit data text, image and voice through radio link. It is found that field observation data can be sent to server within 12km coverage distance by using radio link media communication.

Automatic Weather Station is an integrated system of measuring instruments, interfaces, and data processing and transmission capable of collecting weather data. Weather stations data can be crowd-sourced through Citizen Weather Observer Program (CWOP), powered by Automatic Packet Reporting System (APRS). To further increase the performance of the weather station, a LoRa based modem is used as the transceiver modem. This paper proposes an automatic weather station network using a LoRa-based APRS network. Preliminary results show that the prototyped weather station data can be easily integrated to APRS-IS based network infrastructure.

This chapter presents software and hardware solutions for interconnecting an existing VHF amateur packet radio infrastructure with ‘Winlink 2000' radio email network. Having in mind that a number of households, schools, and offices are equipped with Internet connections, and that many radio amateurs at such locations are active on their VHF (or UHF) digital networks on a daily basis, the connectivity between the two systems will increase the chances for citizens who suffer after disasters such as earthquakes, heavy rains and floods, followed by malfunction in commercial communicating services – to remain electronically wired with the rest of world by email. The chapter provides a tutorial on constructing, installing, and testing a simple packet radio repeater station, additionally equipped with computer programs with ‘Winlink 2000' compatibility.

To communicate with the ground station, nano satellite requires a communication system that serves in real time to regulate the procedure with ground station. One of the missions of nano satellites is the retrieval of telemetry data from sensors that transmitted using APRS technology (Automatic Packet Reporting System). We designed a prototype to monitor sensor by utilizing the APRS. Real-time sensor data was transmitted to monitor through radio using AX.25 protocol. On the transmitter side, an APRS Tracker integrated with a microprocessor ATMEGA 1284P to modulate the AFSK signal. The existence of this AFSK signal is used to transmit and receive telemetry data using handy talky. We use a computer with AGWPE software to demodulate the AFSK signal and UI-View32 to show the telemetry data. The results showed that the telemetry data can be displayed on the receiver side and acquired in real time. The accuracy of temperature sensor received by the receiver is 92.97%, and humidity sensor is 90.57%. There was a delay of 1 second for the reception of telemetry data directly.

The developed system, based on the DSP (Digital Signal Processor), provides an integrated store-and-forward APRS (Automatic Packet Reporting System) payload and OBDH (On Board Data Handling) subsystems at a very low cost and on a single board with dimensions less than 10 cm × 10 cm, thereby enabling a new level of performance for CubeSat-class spacecraft. In this paper, we consider the problem of designing a low-complexity AFSK and GMSK modems for a satellite communication link where the constraints on satellite power budget, antenna size, and data rate are such that the available transmit power, aboard the Picosatellite, is 1 Watt. To cut down the cost of the Picosatellite, we give a particular attention to software optimization due to use of small amount of 8K words Radiation Hardness ROM memory containing the application program. We have defined a methodology approach based on two design steps: algorithmic optimization, and optimal programming using Assembler language. Due to the radiation in space and the constraints of the Picosatellite, some measures regarding volume, mass, power, cost and radiation tolerance, had to be taken into consideration when the system was designed.

This paper purposed to implement the Automatic Antenna Tracking system in order to establish the communication with OSCAR (Orbiting Satellite Carry Amateur Radio) for voice (FM, SSB) and data communications (AX.25, packet radio, APRS). There are more than 5 fully operational Amateur satellites both U/V mode and CUBESAT in orbit act as repeaters or Store/ Forward. The often of the activities that came from International Space Station (ISS) sent out picture to ground station with SLOW SCAN TV(SSTV) data protocol. This research areas covered include Azimuth/Elevation Rotor Design and Schematic Controller Interface design.

The objective of the Internet-based coaxial switching system for an amateur radio station with multiple antenna was to create a system that could choose the appropriate antenna for a radio station in order to reduce the mismatch problem. That is essential because each antenna has specific operating frequency and specific radiation pattern. To control the switching mechanism, the microcontroller was an essential part of this embedded system. The system was implemented with high quality relays having good response in the amateur radio frequency range. System control could be done through personal computer or Android mobile phone. In addition, this system was integrated with a software-defined receiver. The implemented system was capable of selecting appropriate antenna as designed. The attenuation loss and signal reflection were acceptable by conventional amateur radio standards. This system has a user-friendly interface via mobile phone and personal computer. In addition to regular amateur radio setup, this work was tested with a software-defined receiver and it could operate in the similar designed conditions.

This paper presents the results obtained with a new type of spatiotemporal topological dimension implemented within a hypercube, i.e., within a multidimensional database (MDDB) structure formed by the conjunction of several thematic, spatial and temporal dimensions. Our goal is to support efficient SpatioTemporal Exploration and Analysis (STEA) in the context of Automatic Position Reporting System (APRS), the worldwide amateur radio system for position report transmission. Mobile APRS stations are equipped with GPS navigation systems to provide real-time positioning reports. Previous research about the multidimensional approach has proved good potential for spatiotemporal exploration and analysis despite a lack of explicit topological operators (spatial, temporal and spatiotemporal). Our project implemented such operators through a hierarchy of operators that are applied to pairs of instances of objects. At the top of the hierarchy, users can use simple operators such as “same place”, “same time” or “same time, same place”. As they drill down into the hierarchy, more detailed topological operators are made available such as “adjacent immediately after”, “touch during” or more detailed operators. This hierarchy is structured according to four levels of granularity based on cognitive models, generalized relationships and formal models of topological relationships. In this paper, we also describe the generic approach which allows efficient STEA within the multidimensional approach. Finally, we demonstrate that such an implementation offers query run times which permit to maintain a “train-of-thought” during exploration and analysis operations as they are compatible with Newell's cognitive band (query runtime

Highway speed and travel times are generally the standard for evaluating highway network performance. Yet these data are often costly or difficult to obtain. As such, recent research has focused on exploiting new technologies (e.g., cell phones) as cost-effective sources of speed and travel time information. Consistent with this work, a new source of data and an acquisition approach that provides both vehicle speed and travel time measurements from ad hoc probe vehicles at modest cost are presented. In this system, probe vehicles collect Global Positioning System speed, heading, and position data and transmit them over amateur radio frequencies. Frequencies are monitored by personal computers, which are used to receive and process the probe data. System output consists of records containing traveler location, speed, and the time at which data were transmitted. Moreover, these data are managed and maintained as layers of points in a geographic information system and lend themselves to use in several applications. Contrasted with the system described, most traditional speed measurement systems (e.g., loop sensors) are restricted to collecting data at fixed points along major highways where sensors are installed. However, probe data facilitate regional analysis since acquiring information from probe vehicles does not depend on fixed observation points. Some of these applications and advantages of the data are discussed, and a detailed comparison of speed data retrieved from the presented probe system and data collected by traffic loop sensors is provided. The analysis demonstrates that the described probe vehicle system is an effective transportation data source.

To provide reliable data for drift prediction models, field experiments were carried out in the coastal region off Busan port. Four different size of vessels(10, 30, 50, 90G/T ton) were deployed for the experiment. Among them G/T 50ton class vessel was equipped with instruments measuring the currents, winds, headings and trajectory data. In the rest of vessels only the position data were recorded for the purpose of target divergence study. The trajectories of each vessel were measured by DGPS(Differential Global Positioning System) and collected by APRS(Automatic Position Reporting System). The experiment was done in wind of 2~10m/s and current of 0.5~1.5m/s. The leeway was derived by subtracting surface current velocity from target drifting velocity. The leeway rate of G/T 50ton vessel was found to be about 3.6% and the computed leeway speed equation was

A balloonSat weighs up to around 4 kg and soars up to reach altitudes of 100,000 feet or higher using a high altitude balloon with its diameter of 10 to 12 feet mostly, but costs only several hundred dollars. This altitude of the stratosphere provides harsh conditions of tough and significant scientific and engineering challenges. High-altitude balloons can carry small payloads to altitudes higher than 80,000 feet into the stratosphere, in which part of space the conditions and atmosphere are quite similar to those in low-Earth orbit, so as to call it as near-space. In this balloonSat project, the payload systems are developed based upon a cubic satellite, which is equipped with a 16-bit microcontroller; wireless 2.4 GHz modem that transmits signals well to a receiver on the ground consistently upon various cosmic radiation levels in the near-space; the 9-degree sensor that collects and transmits in real time during the whole flight. In the meantime to track the BalloonSat throughout the whole flight so as to recover it safely, the GPS and Automatic Position Reporting System (APRS) are deployed with the balloonSat.

Radio communication has great history of innovations. A hobby which helped in pioneering many innovations in radio communications that we are using today is radio amateurism. Hams are radio amateur hobbyists, which use radio communication to communicate, research, and explore new radio technologies and applications, such as Automatic Packet Reporting System (APRS), which is digital communications information channel for Ham radio. Among other purposes APRS is used to report and map position of any stationary or mobile object via radio. In this paper we presented a low cost APRS client-server infrastructure using Raspberry Pi, APRSdroid, and software defined radio (SDR).

LAPAN-A2 is a 2nd generation of microsatellite developed by the Indonesian National Institute of Aeronautics and Space (LAPAN), Indonesia. This satellite has been launched on September 28, 2015, with several primary missions are: Earth observation using an RGB camera, maritime traffic monitoring using Automatic Identification System (AIS), and supporting disaster mitigation through amateur radio automatic packet reporting system (APRS) and a voice repeater. The installed camera on the satellite can provide imagery with 3.5 m spatial resolution and able to view a swath 7 km wide. This study is attempt to classify and evaluate the accuracy of land cover and land use (LCLU) map classified from the LAPAN-A2 satellite data. As a reference we used the Pleiades-1A Orthorectified imagery data with 0.5 m spatial resolution. Through visual interpretation method, we classified the LCLU into five classess as follows: water body, building, vegetation, road, and bare land. The confusion matrix was applied to evaluate the classification results for three selected area of interest (AOI). We obtained the overall accuracy, producer's accuracy, and user's accuracy are about 61.77%, 61.02%, and 83.78% respectively.

The United States Federal Communications Commission permits licensed amateur radio operators to transmit data using the 144.1 MHz - 148.0 MHz radio frequencies that comprise the amateur 2-meter band. Unfortunately, significant time is needed to transmit large files over 2-meter amateur packet radio networks because the required terminal node controllers (i.e. radio modems) transmit data at a standard rate of 1200 bps. In this paper, we evaluate the performance of the Reno variant of the transmission control protocol and the user datagram protocol when both are used to transmit medical imagery over ns-2 simulated 2-meter amateur packet radio networks. Specifically, we obtain file transmission times while varying protocol segment sizes and channel bit error rates, and find that smaller segment sizes are best for transmitting medical imagery when the bit error rate increases. We also discuss image quality measures as they relate to medical imagery transmitted using the user datagram protocol.

APRS is an abbreviation for Automatic Packet Reporting System, and is a method of broadcasting GPS positioning information in real time from packet radio-equipped stations. It was designed in the early 90’s, but it has seen growth in the last few years due to user-friendly software such as WinAPRS or UI-View, and Kenwood’s APRS enabled radio transceivers becoming available. APRS equipped stations send latitude and longitude information, as well as course, speed and altitude of mobile stations. These are commonly set up for use as Search and Rescue operations or special public events such as parades for tactical overviews. Even the International Space Station and a number of low-earth orbiting satellites have an APRS repeater on board, with amateur earth stations watching positions on their PC screens. Many stations also transmit weather data, which is collected for use by the US Weather Service.

The satellite, as small as the Cubesat concept, requires employment of limited small boards. In the modular architecture, each single subsystem has a dedicated hardware and software. The approach, which has been taken in this paper, based on two design directives: the integration of the maximum subsystems within the same unit taking into account that single subsystems can be setup without modifying the operation of the remaining subsystems, and the elimination of nonessential elements. In this paper, we will describe in details the design of integrated store-and-forward APRS (automatic packet reporting system) payload and OBDH (on board data handling) subsystems using one chip based on the fixed point DSP (digital signal processor) to design a low-cost nanosatellite. By an optimal software design that takes the maximum advantages from DSP architecture facilities, good real time experimental performances have been obtained for the APRS payload and OBDH implemented modules. Due to the environment in space and the constraints of the nanosatellite, different measures had to be taken when the system was designed.

There are several cross-country solar and electric vehicle racing events conducted around the world which demonstrate the capabilities of the cars. The vehicles travel on rural and urban highways, blending in with conventional cars. The vehicles in the event are judged on speed, range, efficiency and performance. The organizers of the events have developed several different methods to track and time the vehicles in order to determine the winner. Usage of an automated process enhances the quality of the scores, reduces the amount of vehicle management work and increases the safety of the event. The use of a Global Positioning Satellite (GPS) system with amateur radio communications is one approach in automating the scoring process. Organizers of the SunDay Challenge-an alternative energy vehicle event in Florida-have developed just such a system for their 70 mile cross-country route. Each vehicle will carry a GPS unit, a computer, a packet converter and a ham radio. Using local amateur radio repeaters, packet radio data messages will be transmitted from the start of the race to the finish, containing GPS location data and other information about each vehicle in the event.

A review of the satellite-based packet radio activities taking place in the Amateur Radio Service is presented. Five projects are discussed. The Digital Communications Experiment (DCE) on UoSAT-OSCAR-11 is a store-and-forward system that is accessed by a limited number of stations around the world designated as DCE gateways. These gateway stations retrieve and store messages forwarded to them via terrestrial packet radio networks. The Japanese FO-12 satellite is a store-and-forward system, and its user interface is much like computer bulletin boards accessed via land lines. It is available for use by all radio amateurs with the required equipment. Both UO-11 and FO-12 are in low earth orbits. The RUDAK experiment and the PACSAT project are also discussed. >

Packet radio communications provides an effective way to interconnect fixed and mobile computer resources. The ALOHA System at the University of Hawaii first introduced this capability in the context of a single-hop system using off-the-shelf RF equipment with all terminals within line of sight of the central station. The packet radio network described in this paper is 1) an extension of the basic Hawaii work to a geographically distributed system involving the use of repeaters to achieve area coverage beyond line of sight, and 2) provides added capabilities for authentication, antijam protection, and coexistence with other possibly different systems in the same band. An overview of the packet radio system concept is given in this paper.