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Methods based on integer ambiguity determination, such as the least-squares ambiguity decorrelation adjustment (LAMBDA) method, are currently used for precise global navigation satellite system (GNSS) differential positioning. In the present paper, the author proposes an ambiguity-free method based on a dedicated mixed (stochastic/deterministic) optimization algorithm that, unlike the LAMBDA method, is capable of providing reliable and accurate results using few observation epochs (e.g., 1-cm accuracy with just two epochs), having the additional advantages of insensitivity to cycle slips and impossibility of wrong ambiguity fixation. In addition, it is demonstrated that the application of the linear (deterministic) part of this algorithm yields the correct baseline results much more easily and quickly than methods requiring integer ambiguity determination, provided the initial approximate coordinates are accurate to a few centimeters. However, the use of ambiguity-free methods requires that the integer character of the ambiguities be preserved so that they can be eliminated; therefore no ionosphere-free combination can be computed and the methods are valid only for short baselines (e.g., less than 10 km).

Methods based on integer ambiguity determination, such as the least-squares ambiguity decorrelation adjustment (LAMBDA) method, are currently used for precise global navigation satellite system (GNSS) differential positioning. In the present paper, the author proposes an ambiguity-free method based on a dedicated mixed (stochastic/deterministic) optimization algorithm that, unlike the LAMBDA method, is capable of providing reliable and accurate results using few observation epochs (e.g., 1-cm accuracy with just two epochs), having the additional advantages of insensitivity to cycle slips and impossibility of wrong ambiguity fixation. In addition, it is demonstrated that the application of the linear (deterministic) part of this algorithm yields the correct baseline results much more easily and quickly than methods requiring integer ambiguity determination, provided the initial approximate coordinates are accurate to a few centimeters. However, the use of ambiguity-free methods requires that the integer character of the ambiguities be preserved so that they can be eliminated; therefore no ionosphere-free combination can be computed and the methods are valid only for short baselines (e.g., less than 10 km).

This paper presents a sensor fusion framework that improves the localization of mobile robots with limited computational resources. It employs an event based Kalman Filter to combine the measurements of a global sensor and an inertial measurement unit (IMU) on an event based schedule, using fewer resources (execution time and bandwidth) but with similar performance when compared to the traditional methods. The event is defined to reflect the necessity of the global information, when the estimation error covariance exceeds a predefined limit. The proposed experimental platforms are based on the LEGO Mindstorm NXT, and consist of a differential wheel mobile robot navigating indoors with a zenithal camera as global sensor, and an Ackermann steering mobile robot navigating outdoors with a SBG Systems GPS accessed through an IGEP board that also serves as datalogger. The IMU in both robots is built using the NXT motor encoders along with one gyroscope, one compass and two accelerometers from Hitecnic, placed according to a particle based dynamic model of the robots. The tests performed reflect the correct performance and low execution time of the proposed framework. The robustness and stability is observed during a long walk test in both indoors and outdoors environments.

Precise point positioning (PPP) involves observations from a single global navigation satellite system (GNSS) receiver and benefits of satellite orbit and clock products obtained from the global infrastructure of permanent stations. PPP avoids the expense and logistic difficulties of deploying a network of GNSS receivers around survey areas in isolated places, such as the arctic or less populated areas. Potential accuracies are at the centimeter level for static applications and at the subdecimeter level for kinematic applications. Static and kinematic PPP based on the processing of global positioning system (GPS) observations is limited by the number of visible satellites, which is often insufficient for urban or mountain applications, or it can be partially obstructed or present multipath effects. Even if a number of GPS satellites are available, the accuracy and reliability can still be affected by poor satellite geometry. One possible way of increasing satellite signal availability and positioning reliability is to integrate GPS and GLONASS observations. This case study deals with the possibilities of combining GPS and GLONASS dual-frequency measurements on the static and kinematic PPP solution to reduce the convergence time and improve the accuracy of the solution. The results show that the addition of the GLONASS constellation does not always improve the convergence of static PPP; the kinematic results (car and walk trajectories) present better accuracy from the GPS1GLONASS solution rather than the GPS-only solution. The MagicGNSS software was used in processing of all observations

Precise point positioning (PPP) involves observations from a single global navigation satellite system (GNSS) receiver and benefits of satellite orbit and clock products obtained from the global infrastructure of permanent stations. PPP avoids the expense and logistic difficulties of deploying a network of GNSS receivers around survey areas in isolated places, such as the arctic or less populated areas. Potential accuracies are at the centimeter level for static applications and at the subdecimeter level for kinematic applications. Static and kinematic PPP based on the processing of global positioning system (GPS) observations is limited by the number of visible satellites, which is often insufficient for urban or mountain applications, or it can be partially obstructed or present multipath effects. Even if a number of GPS satellites are available, the accuracy and reliability can still be affected by poor satellite geometry. One possible way of increasing satellite signal availability and positioning reliability is to integrate GPS and GLONASS observations. This case study deals with the possibilities of combining GPS and GLONASS dual-frequency measurements on the static and kinematic PPP solution to reduce the convergence time and improve the accuracy of the solution. The results show that the addition of the GLONASS constellation does not always improve the convergence of static PPP; the kinematic results (car and walk trajectories) present better accuracy from the GPS1GLONASS solution rather than the GPS-only solution. The MagicGNSS software was used in processing of all observations

This paper presents a sensor fusion framework that improves the localization of mobile robots with limited computational resources. It employs an event based Kalman Filter to combine the measurements of a global sensor and an inertial measurement unit (IMU) on an event based schedule, using fewer resources (execution time and bandwidth) but with similar performance when compared to the traditional methods. The event is defined to reflect the necessity of the global information, when the estimation error covariance exceeds a predefined limit. The proposed experimental platforms are based on the LEGO Mindstorm NXT, and consist of a differential wheel mobile robot navigating indoors with a zenithal camera as global sensor, and an Ackermann steering mobile robot navigating outdoors with a SBG Systems GPS accessed through an IGEP board that also serves as datalogger. The IMU in both robots is built using the NXT motor encoders along with one gyroscope, one compass and two accelerometers from Hitecnic, placed according to a particle based dynamic model of the robots. The tests performed reflect the correct performance and low execution time of the proposed framework. The robustness and stability is observed during a long walk test in both indoors and outdoors environments.

[EN] In the road geometric design process, speed variation along the road segment is one of the most popular criteria to evaluate road consistency, hence the importance of estimating operating speed and its variations. Most of the estimation models are based on speed spot data collection, usually assuming some hypotheses like operating speed remains constant at curves and speed variations take place entirely at preceding tangent. This paper presents the results of the study of the deceleration phenomenon using a new methodology based on data collection by global positioning system devices. By means of this new methodology, not only new and more accurate models can be developed, but also the previous hypotheses can be checked and new studies can be carried out. Tangent-to-curve speed variations have been evaluated, comparing the 85th percentile speed differential (85V) and the differential of the 85th percentile operating speed (V85), analyzing the percentage of deceleration length that takes place at curves, and developing two deceleration models with radius of horizontal curve and parameter of transition curve as explanatory variables.

In recent years interest has increased for precise point positioning (PPP), which provides an alternative to precise relative processing because of its potential as a reliable absolute positioning technique. PPP technique takes advantage of satellite orbit and clock products obtained from the global infrastructure of permanent stations. As a result, PPP requires only one dual-frequency, carrier-phase global positioning system (GPS) receiver on the client side and, thus, avoids the expensive and logistic difficulties of deploying a network of global navigation satellite system (GNSS) receivers around survey areas or in isolated places, such as the Arctic or less populated areas. The broad question of the place of PPP in the future spectrum of space geodetic measurement techniques is addressed in this study by investigating specific aspects of PPP. These aspects involve the following: (1) the time convergence solution in coordinates and accuracy; (2) the observational time required to guarantee the absolute character of the coordinates; (3) the coordinate variations by using rapid and ultrarapid International GNSS Service (IGS) orbits and clock files compared with the final IGS files, which is a useful test for real-time or near-real-time possible users; (4) the comparison of coordinate differences obtained in the postprocessing of daily observation receiver independent exchange (RINEX) files using different software [BERNESE v5.0 along with the four programs in the Precise Point Positioning Software Centre project; Automatic Precise Positioning Service (APPS), Canadian Spatial Reference System Online Global GPS Processing Service (CSRS-PPP), GPS Analysis and Position Software (GAPS), and Magic Global Navigation Satellite System (MagicGNSS) (GMV)]; and (5) the possibilities of the GPS+GLONASS constellation to reduce the convergence time solution and to improve the accuracy of the solution. Some of these five aspects have been partially analyzed in other papers, but th

In recent years interest has increased for precise point positioning (PPP), which provides an alternative to precise relative processing because of its potential as a reliable absolute positioning technique. PPP technique takes advantage of satellite orbit and clock products obtained from the global infrastructure of permanent stations. As a result, PPP requires only one dual-frequency, carrier-phase global positioning system (GPS) receiver on the client side and, thus, avoids the expensive and logistic difficulties of deploying a network of global navigation satellite system (GNSS) receivers around survey areas or in isolated places, such as the Arctic or less populated areas. The broad question of the place of PPP in the future spectrum of space geodetic measurement techniques is addressed in this study by investigating specific aspects of PPP. These aspects involve the following: (1) the time convergence solution in coordinates and accuracy; (2) the observational time required to guarantee the absolute character of the coordinates; (3) the coordinate variations by using rapid and ultrarapid International GNSS Service (IGS) orbits and clock files compared with the final IGS files, which is a useful test for real-time or near-real-time possible users; (4) the comparison of coordinate differences obtained in the postprocessing of daily observation receiver independent exchange (RINEX) files using different software [BERNESE v5.0 along with the four programs in the Precise Point Positioning Software Centre project; Automatic Precise Positioning Service (APPS), Canadian Spatial Reference System Online Global GPS Processing Service (CSRS-PPP), GPS Analysis and Position Software (GAPS), and Magic Global Navigation Satellite System (MagicGNSS) (GMV)]; and (5) the possibilities of the GPS+GLONASS constellation to reduce the convergence time solution and to improve the accuracy of the solution. Some of these five aspects have been partially analyzed in other papers, but th

[ES] Los sistemas de control de crucero adaptativo permiten, adecuando la velocidad, realizar el seguimiento del vehículo precedente en autopistas mientras este vehículo no se detenga. Sin embargo, en áreas urbanas donde la congestión del tráfico obliga a continuas detenciones, este sistema pierde funcionalidad ya que, una vez detenido el vehículo, el conductor debe reactivar el sistema. En este artículo, se presenta un sistema de control de velocidad mediante lógica borrosa para situaciones continuadas de parada y arranque, en las que la velocidad del vehículo es inferior a diez kilómetros por hora. El sistema se ha implantado y probado en un vehículo comercial con excelentes resultados., [EN] The adaptive cruise control systems are capable of adapting the speed to the precedent car in highways as long as the car do not stop. However, in urban areas where the traffic flow can cause stop and go manoeuvres continuously, this system is not very useful due to the necessity of re-start it once the car is stopped. In this paper, an speed control based on fuzzy logic for continuous stop and go manoeuvres is presented where the speed car is up to ten kilometres per hour. The system has been tested with two Citroën C3 vehicles, one of them full automated, in the Instituto de Automática Industrial facilities with great results.

[ES] Los sistemas de control de crucero adaptativo permiten, adecuando la velocidad, realizar el seguimiento del vehículo precedente en autopistas mientras este vehículo no se detenga. Sin embargo, en áreas urbanas donde la congestión del tráfico obliga a continuas detenciones, este sistema pierde funcionalidad ya que, una vez detenido el vehículo, el conductor debe reactivar el sistema. En este artículo, se presenta un sistema de control de velocidad mediante lógica borrosa para situaciones continuadas de parada y arranque, en las que la velocidad del vehículo es inferior a diez kilómetros por hora. El sistema se ha implantado y probado en un vehículo comercial con excelentes resultados., [EN] The adaptive cruise control systems are capable of adapting the speed to the precedent car in highways as long as the car do not stop. However, in urban areas where the traffic flow can cause stop and go manoeuvres continuously, this system is not very useful due to the necessity of re-start it once the car is stopped. In this paper, an speed control based on fuzzy logic for continuous stop and go manoeuvres is presented where the speed car is up to ten kilometres per hour. The system has been tested with two Citroën C3 vehicles, one of them full automated, in the Instituto de Automática Industrial facilities with great results.

[ES] Los sistemas de control de crucero adaptativo permiten, adecuando la velocidad, realizar el seguimiento del vehículo precedente en autopistas mientras este vehículo no se detenga. Sin embargo, en áreas urbanas donde la congestión del tráfico obliga a continuas detenciones, este sistema pierde funcionalidad ya que, una vez detenido el vehículo, el conductor debe reactivar el sistema. En este artículo, se presenta un sistema de control de velocidad mediante lógica borrosa para situaciones continuadas de parada y arranque, en las que la velocidad del vehículo es inferior a diez kilómetros por hora. El sistema se ha implantado y probado en un vehículo comercial con excelentes resultados., [EN] The adaptive cruise control systems are capable of adapting the speed to the precedent car in highways as long as the car do not stop. However, in urban areas where the traffic flow can cause stop and go manoeuvres continuously, this system is not very useful due to the necessity of re-start it once the car is stopped. In this paper, an speed control based on fuzzy logic for continuous stop and go manoeuvres is presented where the speed car is up to ten kilometres per hour. The system has been tested with two Citroën C3 vehicles, one of them full automated, in the Instituto de Automática Industrial facilities with great results.

[ES] Los sistemas de control de crucero adaptativo permiten, adecuando la velocidad, realizar el seguimiento del vehículo precedente en autopistas mientras este vehículo no se detenga. Sin embargo, en áreas urbanas donde la congestión del tráfico obliga a continuas detenciones, este sistema pierde funcionalidad ya que, una vez detenido el vehículo, el conductor debe reactivar el sistema. En este artículo, se presenta un sistema de control de velocidad mediante lógica borrosa para situaciones continuadas de parada y arranque, en las que la velocidad del vehículo es inferior a diez kilómetros por hora. El sistema se ha implantado y probado en un vehículo comercial con excelentes resultados., [EN] The adaptive cruise control systems are capable of adapting the speed to the precedent car in highways as long as the car do not stop. However, in urban areas where the traffic flow can cause stop and go manoeuvres continuously, this system is not very useful due to the necessity of re-start it once the car is stopped. In this paper, an speed control based on fuzzy logic for continuous stop and go manoeuvres is presented where the speed car is up to ten kilometres per hour. The system has been tested with two Citroën C3 vehicles, one of them full automated, in the Instituto de Automática Industrial facilities with great results.

[ES] Los sistemas de control de crucero adaptativo permiten, adecuando la velocidad, realizar el seguimiento del vehículo precedente en autopistas mientras este vehículo no se detenga. Sin embargo, en áreas urbanas donde la congestión del tráfico obliga a continuas detenciones, este sistema pierde funcionalidad ya que, una vez detenido el vehículo, el conductor debe reactivar el sistema. En este artículo, se presenta un sistema de control de velocidad mediante lógica borrosa para situaciones continuadas de parada y arranque, en las que la velocidad del vehículo es inferior a diez kilómetros por hora. El sistema se ha implantado y probado en un vehículo comercial con excelentes resultados., [EN] The adaptive cruise control systems are capable of adapting the speed to the precedent car in highways as long as the car do not stop. However, in urban areas where the traffic flow can cause stop and go manoeuvres continuously, this system is not very useful due to the necessity of re-start it once the car is stopped. In this paper, an speed control based on fuzzy logic for continuous stop and go manoeuvres is presented where the speed car is up to ten kilometres per hour. The system has been tested with two Citroën C3 vehicles, one of them full automated, in the Instituto de Automática Industrial facilities with great results.

[ES] Los sistemas de control de crucero adaptativo permiten, adecuando la velocidad, realizar el seguimiento del vehículo precedente en autopistas mientras este vehículo no se detenga. Sin embargo, en áreas urbanas donde la congestión del tráfico obliga a continuas detenciones, este sistema pierde funcionalidad ya que, una vez detenido el vehículo, el conductor debe reactivar el sistema. En este artículo, se presenta un sistema de control de velocidad mediante lógica borrosa para situaciones continuadas de parada y arranque, en las que la velocidad del vehículo es inferior a diez kilómetros por hora. El sistema se ha implantado y probado en un vehículo comercial con excelentes resultados., [EN] The adaptive cruise control systems are capable of adapting the speed to the precedent car in highways as long as the car do not stop. However, in urban areas where the traffic flow can cause stop and go manoeuvres continuously, this system is not very useful due to the necessity of re-start it once the car is stopped. In this paper, an speed control based on fuzzy logic for continuous stop and go manoeuvres is presented where the speed car is up to ten kilometres per hour. The system has been tested with two Citroën C3 vehicles, one of them full automated, in the Instituto de Automática Industrial facilities with great results.

[ES] Uno de los objetivos más importantes de los Sistemas Inteligentes de Transporte (ITS) es evitar la pérdida de precisión en el posicionamiento y guiado del vehículo, debido a la disminución en la calidad de la señal del Sistema de Posicionamiento Global (GPS). En este artículo, se presenta un sistema de posicionamiento formado por la combinación de un GPS con una unidad de medida inercial ayudada por los sensores embarcados en el coche para realizar el guiado. En función de la precisión proporcionada por el GPS, el sistema discrimina entre tres posibles comportamientos: 1) Si la precisión es centimétrica, el GPS se encarga en solitario del guiado. 2) Si no se recibe la señal GPS, el control lo toma la unidad inercial. 3) Si la precisión de la señal del GPS no es centimétrica, la posición del vehículo se calcula mediante una combinación de ambas medidas. El sistema se ha instalado en un Citroën C3 Pluriel. Los resultados muestran un correcto comportamiento del vehículo en diferentes situaciones y prueban la necesidad de integrar la información sensorial para realizar un control de navegación óptimo., [EN] Loss of accuracy in automated vehicle position control systems due to Global Positioning System (GPS) signal quality is currently one of the most studied research topics in the field of Intelligent Transportation Systems (ITS). This paper presents an integrated positioning system that combines a GPS with onboard sensors and an Inertial Measurement Unit (IMU) to perform autonomous vehicle guidance. Depending on GPS precision, the system discriminates which positioning is most appropriate from three different possibilities: 1) real-time kinematic differential global positioning system (RTK-DGPS) is working at the highest positioning accuracy (1 cm). In this instance, GPS data are used as the main sensory supply; 2) total DGPS signal loss. Now, the IMU control system takes control; 3) centimeter accuracy is lost. In this instance, GPS and IMU measurements are integrated to determine the true positioning. This system has been installed in a Citroën C3 Pluriel car, where all the actuators were automated to achieve human-like driving. Experimental results show the car's behavior in diverse situations and prove that the test-bed vehicle can maintain automatic navigation even when GPS positioning is unavailable. The results also show the need to combine sensory information to obtain optimum navigation control in any circumstance.

[ES] Uno de los objetivos más importantes de los Sistemas Inteligentes de Transporte (ITS) es evitar la pérdida de precisión en el posicionamiento y guiado del vehículo, debido a la disminución en la calidad de la señal del Sistema de Posicionamiento Global (GPS). En este artículo, se presenta un sistema de posicionamiento formado por la combinación de un GPS con una unidad de medida inercial ayudada por los sensores embarcados en el coche para realizar el guiado. En función de la precisión proporcionada por el GPS, el sistema discrimina entre tres posibles comportamientos: 1) Si la precisión es centimétrica, el GPS se encarga en solitario del guiado. 2) Si no se recibe la señal GPS, el control lo toma la unidad inercial. 3) Si la precisión de la señal del GPS no es centimétrica, la posición del vehículo se calcula mediante una combinación de ambas medidas. El sistema se ha instalado en un Citroën C3 Pluriel. Los resultados muestran un correcto comportamiento del vehículo en diferentes situaciones y prueban la necesidad de integrar la información sensorial para realizar un control de navegación óptimo., [EN] Loss of accuracy in automated vehicle position control systems due to Global Positioning System (GPS) signal quality is currently one of the most studied research topics in the field of Intelligent Transportation Systems (ITS). This paper presents an integrated positioning system that combines a GPS with onboard sensors and an Inertial Measurement Unit (IMU) to perform autonomous vehicle guidance. Depending on GPS precision, the system discriminates which positioning is most appropriate from three different possibilities: 1) real-time kinematic differential global positioning system (RTK-DGPS) is working at the highest positioning accuracy (1 cm). In this instance, GPS data are used as the main sensory supply; 2) total DGPS signal loss. Now, the IMU control system takes control; 3) centimeter accuracy is lost. In this instance, GPS and IMU measurements are integrated to determine the true positioning. This system has been installed in a Citroën C3 Pluriel car, where all the actuators were automated to achieve human-like driving. Experimental results show the car's behavior in diverse situations and prove that the test-bed vehicle can maintain automatic navigation even when GPS positioning is unavailable. The results also show the need to combine sensory information to obtain optimum navigation control in any circumstance.

[ES] Uno de los objetivos más importantes de los Sistemas Inteligentes de Transporte (ITS) es evitar la pérdida de precisión en el posicionamiento y guiado del vehículo, debido a la disminución en la calidad de la señal del Sistema de Posicionamiento Global (GPS). En este artículo, se presenta un sistema de posicionamiento formado por la combinación de un GPS con una unidad de medida inercial ayudada por los sensores embarcados en el coche para realizar el guiado. En función de la precisión proporcionada por el GPS, el sistema discrimina entre tres posibles comportamientos: 1) Si la precisión es centimétrica, el GPS se encarga en solitario del guiado. 2) Si no se recibe la señal GPS, el control lo toma la unidad inercial. 3) Si la precisión de la señal del GPS no es centimétrica, la posición del vehículo se calcula mediante una combinación de ambas medidas. El sistema se ha instalado en un Citroën C3 Pluriel. Los resultados muestran un correcto comportamiento del vehículo en diferentes situaciones y prueban la necesidad de integrar la información sensorial para realizar un control de navegación óptimo., [EN] Loss of accuracy in automated vehicle position control systems due to Global Positioning System (GPS) signal quality is currently one of the most studied research topics in the field of Intelligent Transportation Systems (ITS). This paper presents an integrated positioning system that combines a GPS with onboard sensors and an Inertial Measurement Unit (IMU) to perform autonomous vehicle guidance. Depending on GPS precision, the system discriminates which positioning is most appropriate from three different possibilities: 1) real-time kinematic differential global positioning system (RTK-DGPS) is working at the highest positioning accuracy (1 cm). In this instance, GPS data are used as the main sensory supply; 2) total DGPS signal loss. Now, the IMU control system takes control; 3) centimeter accuracy is lost. In this instance, GPS and IMU measurements are integrated to determine the true positioning. This system has been installed in a Citroën C3 Pluriel car, where all the actuators were automated to achieve human-like driving. Experimental results show the car's behavior in diverse situations and prove that the test-bed vehicle can maintain automatic navigation even when GPS positioning is unavailable. The results also show the need to combine sensory information to obtain optimum navigation control in any circumstance.

[ES] Uno de los objetivos más importantes de los Sistemas Inteligentes de Transporte (ITS) es evitar la pérdida de precisión en el posicionamiento y guiado del vehículo, debido a la disminución en la calidad de la señal del Sistema de Posicionamiento Global (GPS). En este artículo, se presenta un sistema de posicionamiento formado por la combinación de un GPS con una unidad de medida inercial ayudada por los sensores embarcados en el coche para realizar el guiado. En función de la precisión proporcionada por el GPS, el sistema discrimina entre tres posibles comportamientos: 1) Si la precisión es centimétrica, el GPS se encarga en solitario del guiado. 2) Si no se recibe la señal GPS, el control lo toma la unidad inercial. 3) Si la precisión de la señal del GPS no es centimétrica, la posición del vehículo se calcula mediante una combinación de ambas medidas. El sistema se ha instalado en un Citroën C3 Pluriel. Los resultados muestran un correcto comportamiento del vehículo en diferentes situaciones y prueban la necesidad de integrar la información sensorial para realizar un control de navegación óptimo., [EN] Loss of accuracy in automated vehicle position control systems due to Global Positioning System (GPS) signal quality is currently one of the most studied research topics in the field of Intelligent Transportation Systems (ITS). This paper presents an integrated positioning system that combines a GPS with onboard sensors and an Inertial Measurement Unit (IMU) to perform autonomous vehicle guidance. Depending on GPS precision, the system discriminates which positioning is most appropriate from three different possibilities: 1) real-time kinematic differential global positioning system (RTK-DGPS) is working at the highest positioning accuracy (1 cm). In this instance, GPS data are used as the main sensory supply; 2) total DGPS signal loss. Now, the IMU control system takes control; 3) centimeter accuracy is lost. In this instance, GPS and IMU measurements are integrated to determine the true positioning. This system has been installed in a Citroën C3 Pluriel car, where all the actuators were automated to achieve human-like driving. Experimental results show the car's behavior in diverse situations and prove that the test-bed vehicle can maintain automatic navigation even when GPS positioning is unavailable. The results also show the need to combine sensory information to obtain optimum navigation control in any circumstance.

[ES] Uno de los objetivos más importantes de los Sistemas Inteligentes de Transporte (ITS) es evitar la pérdida de precisión en el posicionamiento y guiado del vehículo, debido a la disminución en la calidad de la señal del Sistema de Posicionamiento Global (GPS). En este artículo, se presenta un sistema de posicionamiento formado por la combinación de un GPS con una unidad de medida inercial ayudada por los sensores embarcados en el coche para realizar el guiado. En función de la precisión proporcionada por el GPS, el sistema discrimina entre tres posibles comportamientos: 1) Si la precisión es centimétrica, el GPS se encarga en solitario del guiado. 2) Si no se recibe la señal GPS, el control lo toma la unidad inercial. 3) Si la precisión de la señal del GPS no es centimétrica, la posición del vehículo se calcula mediante una combinación de ambas medidas. El sistema se ha instalado en un Citroën C3 Pluriel. Los resultados muestran un correcto comportamiento del vehículo en diferentes situaciones y prueban la necesidad de integrar la información sensorial para realizar un control de navegación óptimo., [EN] Loss of accuracy in automated vehicle position control systems due to Global Positioning System (GPS) signal quality is currently one of the most studied research topics in the field of Intelligent Transportation Systems (ITS). This paper presents an integrated positioning system that combines a GPS with onboard sensors and an Inertial Measurement Unit (IMU) to perform autonomous vehicle guidance. Depending on GPS precision, the system discriminates which positioning is most appropriate from three different possibilities: 1) real-time kinematic differential global positioning system (RTK-DGPS) is working at the highest positioning accuracy (1 cm). In this instance, GPS data are used as the main sensory supply; 2) total DGPS signal loss. Now, the IMU control system takes control; 3) centimeter accuracy is lost. In this instance, GPS and IMU measurements are integrated to determine the true positioning. This system has been installed in a Citroën C3 Pluriel car, where all the actuators were automated to achieve human-like driving. Experimental results show the car's behavior in diverse situations and prove that the test-bed vehicle can maintain automatic navigation even when GPS positioning is unavailable. The results also show the need to combine sensory information to obtain optimum navigation control in any circumstance.