The Experts below are selected from a list of 3213 Experts worldwide ranked by ideXlab platform
Harry Lahrmann - One of the best experts on this subject based on the ideXlab platform.
-
Reliability of Bluetooth Technology for Travel Time Estimation
Journal of Intelligent Transportation Systems: Technology Planning and Operations, 2015Co-Authors: Bahar Namaki Araghi, Rajesh Krishnan, Jonas Hammershøj Olesen, Lars Tørholm Christensen, Harry LahrmannAbstract:Abstract A unique Bluetooth-enabled device may be detected several times or not at all when it passes a sensor location. This depends mainly on the strength and speed of a transmitting device, discovery procedure, location of the device relative to the Bluetooth sensor, the Bluetooth sensor's ping cycle (0.1 seconds), the size and shape of the sensor's Detection Zone, and the time span that the Bluetooth-enabled device is within the Detection Zone. The influences of size of Bluetooth sensor Detection Zones and Bluetooth discovery procedure on multiple Detection events have been mentioned in previous research. However, their corresponding impacts on accuracy and reliability of estimated travel time have not been evaluated. In this study, a controlled field experiment is conducted to collect both Bluetooth and GPS data for 1000 trips to be used as the basis for evaluation. Data obtained by GPS logger is used to calculate actual travel time, referred to as ground truth, and to geo-code the Bluetooth Detection events. In this setting, reliability is defined as the percentage of devices captured per trip during the experiment. It is found that, on average, Bluetooth-enabled devices will be detected 80% of the time while passing a sensor location. The impact of location ambiguity caused by size of Detection Zone is evaluated using geo-coded Bluetooth data. Results show that more than 80% of the Detection events are recorded within the range of 100 meters from the sensor centre line. It is also shown that short-range antennae detect Bluetooth-enabled devices in a closer location to the sensor, thus providing a more accurate travel time estimate. However, the smaller the size of the Detection Zone, the lower the penetration rate, which could itself influence the accuracy of estimates. Therefore, there has to be a trade-off between acceptable level of location ambiguity and penetration rate for configuration and coverage of the antennae.\nAbstract A unique Bluetooth-enabled device may be detected several times or not at all when it passes a sensor location. This depends mainly on the strength and speed of a transmitting device, discovery procedure, location of the device relative to the Bluetooth sensor, the Bluetooth sensor's ping cycle (0.1 seconds), the size and shape of the sensor's Detection Zone, and the time span that the Bluetooth-enabled device is within the Detection Zone. The influences of size of Bluetooth sensor Detection Zones and Bluetooth discovery procedure on multiple Detection events have been mentioned in previous research. However, their corresponding impacts on accuracy and reliability of estimated travel time have not been evaluated. In this study, a controlled field experiment is conducted to collect both Bluetooth and GPS data for 1000 trips to be used as the basis for evaluation. Data obtained by GPS logger is used to calculate actual travel time, referred to as ground truth, and to geo-code the Bluetooth Detection events. In this setting, reliability is defined as the percentage of devices captured per trip during the experiment. It is found that, on average, Bluetooth-enabled devices will be detected 80% of the time while passing a sensor location. The impact of location ambiguity caused by size of Detection Zone is evaluated using geo-coded Bluetooth data. Results show that more than 80% of the Detection events are recorded within the range of 100 meters from the sensor centre line. It is also shown that short-range antennae detect Bluetooth-enabled devices in a closer location to the sensor, thus providing a more accurate travel time estimate. However, the smaller the size of the Detection Zone, the lower the penetration rate, which could itself influence the accuracy of estimates. Therefore, there has to be a trade-off between acceptable level of location ambiguity and penetration rate for configuration and coverage of the antennae.
-
Reliability of Bluetooth Technology for Travel Time Estimation
Journal of Intelligent Transportation Systems, 2014Co-Authors: Bahar Namaki Araghi, Rajesh Krishnan, L.t. Christensen, Jonas Hammershoj Olesen, Harry LahrmannAbstract:A unique Bluetooth-enabled device may be detected several times or not at all when it passes a sensor location. This depends mainly on the strength and speed of a transmitting device, discovery procedure, location of the device relative to the Bluetooth sensor, the Bluetooth sensor's ping cycle (0.1 s), the size and shape of the sensor's Detection Zone, and the time span for which the Bluetooth-enabled device is within the Detection Zone. The influences of size of Bluetooth sensor Detection Zones and Bluetooth discovery procedure on multiple Detection events have been mentioned in previous research. However, their corresponding impacts on accuracy and reliability of estimated travel time have not been evaluated. In this study, a controlled field experiment is conducted to collect both Bluetooth and global positioning system (GPS) data for 1000 trips to be used as the basis for evaluation. Data obtained by GPS logger are used to calculate actual travel time, referred to as ground truth, and to geo-code the...
-
Use of low-level sensor data to improve the accuracy of bluetooth-based travel time estimation
Transportation Research Record, 2013Co-Authors: Bahar Namaki Araghi, L.t. Christensen, Jonas Hammershoj Olesen, R. Krishnan, Harry LahrmannAbstract:Bluetooth sensors have a large Detection Zone compared with other static vehicle reidentification systems. A larger Detection Zone increases the probability of detecting a Bluetooth-enabled device in a fast-moving vehicle, yet increases the probability of multiple Detection events being triggered by a single device. The latter situation could lead to location ambiguity and could reduce the accuracy of travel time estimation. Therefore, the accuracy of travel time estimation by Bluetooth technology depends on how location ambiguity is handled by the estimation method. The issue of multiple Detection events in the context of travel time estimation by Bluetooth technology has been considered by various researchers. However, treatment of this issue has been simplistic. Most previous studies have used the first Detection event (enter-enter) as the best estimate. No systematic analysis has been conducted to explore the most accurate method of travel time estimation with multiple Detection events. In this study, different aspects of the Bluetooth Detection Zone, including size and impact on the accuracy of travel time estimation, were discussed. Four methods were applied to estimate travel time: enter-enter, leave-leave, peak-peak, and combined. These methods were developed on the basis of various technical considerations related to multiple Detection events. A controlled field experiment was conducted to evaluate the accuracy of the methods through comparison with the ground truth travel time data measured by Global Positioning System technology. The results showed that the accuracy of the combined and peak-peak methods was higher than that of the other methods and that the employment of the first Detection event did not necessarily yield the best travel time estimation.
-
Use of {Low}-{Level} {Sensor} {Data} to {Improve} the {Accuracy} of {Bluetooth}-{Based} {Travel} {Time} {Estimation}
Transportation Research Record, 2013Co-Authors: Bahar Namaki Araghi, Rajesh Krishnan, L.t. Christensen, Jonas Hammershoj Olesen, Harry LahrmannAbstract:Bluetooth sensors have a large Detection Zone compared with other static vehicle reidentification systems. A larger Detection Zone increases the probability of detecting a Bluetooth-enabled device in a fast-moving vehicle, yet increases the probability of multiple Detection events being triggered by a single device. The latter situation could lead to location ambiguity and could reduce the accuracy of travel time estimation. Therefore, the accuracy of travel time estimation by Bluetooth technology depends on how location ambiguity is handled by the estimation method. The issue of multiple Detection events in the context of travel time estimation by Bluetooth technology has been considered by various researchers. However, treatment of this issue has been simplistic. Most previous studies have used the first Detection event (enter enter) as the best estimate. No systematic analysis has been conducted to explore the most accurate method of travel time estimation with multiple Detection events. In this study, different aspects of the Bluetooth Detection Zone, including size and impact on the accuracy of travel time estimation, were discussed. Four methods were applied to estimate travel time: enter enter, leave leave, peak peak, and combined. These methods were developed on the basis of various technical considerations related to multiple Detection events. A controlled field experiment was conducted to evaluate the accuracy of the methods through comparison with the ground truth travel time data measured by Global Positioning System technology. The results showed that the accuracy of the combined and peak peak methods was higher than that of the other methods and that the employment of the first Detection event did not necessarily yield the best travel time estimation.
Bahar Namaki Araghi - One of the best experts on this subject based on the ideXlab platform.
-
Reliability of Bluetooth Technology for Travel Time Estimation
Journal of Intelligent Transportation Systems: Technology Planning and Operations, 2015Co-Authors: Bahar Namaki Araghi, Rajesh Krishnan, Jonas Hammershøj Olesen, Lars Tørholm Christensen, Harry LahrmannAbstract:Abstract A unique Bluetooth-enabled device may be detected several times or not at all when it passes a sensor location. This depends mainly on the strength and speed of a transmitting device, discovery procedure, location of the device relative to the Bluetooth sensor, the Bluetooth sensor's ping cycle (0.1 seconds), the size and shape of the sensor's Detection Zone, and the time span that the Bluetooth-enabled device is within the Detection Zone. The influences of size of Bluetooth sensor Detection Zones and Bluetooth discovery procedure on multiple Detection events have been mentioned in previous research. However, their corresponding impacts on accuracy and reliability of estimated travel time have not been evaluated. In this study, a controlled field experiment is conducted to collect both Bluetooth and GPS data for 1000 trips to be used as the basis for evaluation. Data obtained by GPS logger is used to calculate actual travel time, referred to as ground truth, and to geo-code the Bluetooth Detection events. In this setting, reliability is defined as the percentage of devices captured per trip during the experiment. It is found that, on average, Bluetooth-enabled devices will be detected 80% of the time while passing a sensor location. The impact of location ambiguity caused by size of Detection Zone is evaluated using geo-coded Bluetooth data. Results show that more than 80% of the Detection events are recorded within the range of 100 meters from the sensor centre line. It is also shown that short-range antennae detect Bluetooth-enabled devices in a closer location to the sensor, thus providing a more accurate travel time estimate. However, the smaller the size of the Detection Zone, the lower the penetration rate, which could itself influence the accuracy of estimates. Therefore, there has to be a trade-off between acceptable level of location ambiguity and penetration rate for configuration and coverage of the antennae.\nAbstract A unique Bluetooth-enabled device may be detected several times or not at all when it passes a sensor location. This depends mainly on the strength and speed of a transmitting device, discovery procedure, location of the device relative to the Bluetooth sensor, the Bluetooth sensor's ping cycle (0.1 seconds), the size and shape of the sensor's Detection Zone, and the time span that the Bluetooth-enabled device is within the Detection Zone. The influences of size of Bluetooth sensor Detection Zones and Bluetooth discovery procedure on multiple Detection events have been mentioned in previous research. However, their corresponding impacts on accuracy and reliability of estimated travel time have not been evaluated. In this study, a controlled field experiment is conducted to collect both Bluetooth and GPS data for 1000 trips to be used as the basis for evaluation. Data obtained by GPS logger is used to calculate actual travel time, referred to as ground truth, and to geo-code the Bluetooth Detection events. In this setting, reliability is defined as the percentage of devices captured per trip during the experiment. It is found that, on average, Bluetooth-enabled devices will be detected 80% of the time while passing a sensor location. The impact of location ambiguity caused by size of Detection Zone is evaluated using geo-coded Bluetooth data. Results show that more than 80% of the Detection events are recorded within the range of 100 meters from the sensor centre line. It is also shown that short-range antennae detect Bluetooth-enabled devices in a closer location to the sensor, thus providing a more accurate travel time estimate. However, the smaller the size of the Detection Zone, the lower the penetration rate, which could itself influence the accuracy of estimates. Therefore, there has to be a trade-off between acceptable level of location ambiguity and penetration rate for configuration and coverage of the antennae.
-
Reliability of Bluetooth Technology for Travel Time Estimation
Journal of Intelligent Transportation Systems, 2014Co-Authors: Bahar Namaki Araghi, Rajesh Krishnan, L.t. Christensen, Jonas Hammershoj Olesen, Harry LahrmannAbstract:A unique Bluetooth-enabled device may be detected several times or not at all when it passes a sensor location. This depends mainly on the strength and speed of a transmitting device, discovery procedure, location of the device relative to the Bluetooth sensor, the Bluetooth sensor's ping cycle (0.1 s), the size and shape of the sensor's Detection Zone, and the time span for which the Bluetooth-enabled device is within the Detection Zone. The influences of size of Bluetooth sensor Detection Zones and Bluetooth discovery procedure on multiple Detection events have been mentioned in previous research. However, their corresponding impacts on accuracy and reliability of estimated travel time have not been evaluated. In this study, a controlled field experiment is conducted to collect both Bluetooth and global positioning system (GPS) data for 1000 trips to be used as the basis for evaluation. Data obtained by GPS logger are used to calculate actual travel time, referred to as ground truth, and to geo-code the...
-
Use of low-level sensor data to improve the accuracy of bluetooth-based travel time estimation
Transportation Research Record, 2013Co-Authors: Bahar Namaki Araghi, L.t. Christensen, Jonas Hammershoj Olesen, R. Krishnan, Harry LahrmannAbstract:Bluetooth sensors have a large Detection Zone compared with other static vehicle reidentification systems. A larger Detection Zone increases the probability of detecting a Bluetooth-enabled device in a fast-moving vehicle, yet increases the probability of multiple Detection events being triggered by a single device. The latter situation could lead to location ambiguity and could reduce the accuracy of travel time estimation. Therefore, the accuracy of travel time estimation by Bluetooth technology depends on how location ambiguity is handled by the estimation method. The issue of multiple Detection events in the context of travel time estimation by Bluetooth technology has been considered by various researchers. However, treatment of this issue has been simplistic. Most previous studies have used the first Detection event (enter-enter) as the best estimate. No systematic analysis has been conducted to explore the most accurate method of travel time estimation with multiple Detection events. In this study, different aspects of the Bluetooth Detection Zone, including size and impact on the accuracy of travel time estimation, were discussed. Four methods were applied to estimate travel time: enter-enter, leave-leave, peak-peak, and combined. These methods were developed on the basis of various technical considerations related to multiple Detection events. A controlled field experiment was conducted to evaluate the accuracy of the methods through comparison with the ground truth travel time data measured by Global Positioning System technology. The results showed that the accuracy of the combined and peak-peak methods was higher than that of the other methods and that the employment of the first Detection event did not necessarily yield the best travel time estimation.
-
Use of {Low}-{Level} {Sensor} {Data} to {Improve} the {Accuracy} of {Bluetooth}-{Based} {Travel} {Time} {Estimation}
Transportation Research Record, 2013Co-Authors: Bahar Namaki Araghi, Rajesh Krishnan, L.t. Christensen, Jonas Hammershoj Olesen, Harry LahrmannAbstract:Bluetooth sensors have a large Detection Zone compared with other static vehicle reidentification systems. A larger Detection Zone increases the probability of detecting a Bluetooth-enabled device in a fast-moving vehicle, yet increases the probability of multiple Detection events being triggered by a single device. The latter situation could lead to location ambiguity and could reduce the accuracy of travel time estimation. Therefore, the accuracy of travel time estimation by Bluetooth technology depends on how location ambiguity is handled by the estimation method. The issue of multiple Detection events in the context of travel time estimation by Bluetooth technology has been considered by various researchers. However, treatment of this issue has been simplistic. Most previous studies have used the first Detection event (enter enter) as the best estimate. No systematic analysis has been conducted to explore the most accurate method of travel time estimation with multiple Detection events. In this study, different aspects of the Bluetooth Detection Zone, including size and impact on the accuracy of travel time estimation, were discussed. Four methods were applied to estimate travel time: enter enter, leave leave, peak peak, and combined. These methods were developed on the basis of various technical considerations related to multiple Detection events. A controlled field experiment was conducted to evaluate the accuracy of the methods through comparison with the ground truth travel time data measured by Global Positioning System technology. The results showed that the accuracy of the combined and peak peak methods was higher than that of the other methods and that the employment of the first Detection event did not necessarily yield the best travel time estimation.
L.t. Christensen - One of the best experts on this subject based on the ideXlab platform.
-
Reliability of Bluetooth Technology for Travel Time Estimation
Journal of Intelligent Transportation Systems, 2014Co-Authors: Bahar Namaki Araghi, Rajesh Krishnan, L.t. Christensen, Jonas Hammershoj Olesen, Harry LahrmannAbstract:A unique Bluetooth-enabled device may be detected several times or not at all when it passes a sensor location. This depends mainly on the strength and speed of a transmitting device, discovery procedure, location of the device relative to the Bluetooth sensor, the Bluetooth sensor's ping cycle (0.1 s), the size and shape of the sensor's Detection Zone, and the time span for which the Bluetooth-enabled device is within the Detection Zone. The influences of size of Bluetooth sensor Detection Zones and Bluetooth discovery procedure on multiple Detection events have been mentioned in previous research. However, their corresponding impacts on accuracy and reliability of estimated travel time have not been evaluated. In this study, a controlled field experiment is conducted to collect both Bluetooth and global positioning system (GPS) data for 1000 trips to be used as the basis for evaluation. Data obtained by GPS logger are used to calculate actual travel time, referred to as ground truth, and to geo-code the...
-
Use of low-level sensor data to improve the accuracy of bluetooth-based travel time estimation
Transportation Research Record, 2013Co-Authors: Bahar Namaki Araghi, L.t. Christensen, Jonas Hammershoj Olesen, R. Krishnan, Harry LahrmannAbstract:Bluetooth sensors have a large Detection Zone compared with other static vehicle reidentification systems. A larger Detection Zone increases the probability of detecting a Bluetooth-enabled device in a fast-moving vehicle, yet increases the probability of multiple Detection events being triggered by a single device. The latter situation could lead to location ambiguity and could reduce the accuracy of travel time estimation. Therefore, the accuracy of travel time estimation by Bluetooth technology depends on how location ambiguity is handled by the estimation method. The issue of multiple Detection events in the context of travel time estimation by Bluetooth technology has been considered by various researchers. However, treatment of this issue has been simplistic. Most previous studies have used the first Detection event (enter-enter) as the best estimate. No systematic analysis has been conducted to explore the most accurate method of travel time estimation with multiple Detection events. In this study, different aspects of the Bluetooth Detection Zone, including size and impact on the accuracy of travel time estimation, were discussed. Four methods were applied to estimate travel time: enter-enter, leave-leave, peak-peak, and combined. These methods were developed on the basis of various technical considerations related to multiple Detection events. A controlled field experiment was conducted to evaluate the accuracy of the methods through comparison with the ground truth travel time data measured by Global Positioning System technology. The results showed that the accuracy of the combined and peak-peak methods was higher than that of the other methods and that the employment of the first Detection event did not necessarily yield the best travel time estimation.
-
Use of {Low}-{Level} {Sensor} {Data} to {Improve} the {Accuracy} of {Bluetooth}-{Based} {Travel} {Time} {Estimation}
Transportation Research Record, 2013Co-Authors: Bahar Namaki Araghi, Rajesh Krishnan, L.t. Christensen, Jonas Hammershoj Olesen, Harry LahrmannAbstract:Bluetooth sensors have a large Detection Zone compared with other static vehicle reidentification systems. A larger Detection Zone increases the probability of detecting a Bluetooth-enabled device in a fast-moving vehicle, yet increases the probability of multiple Detection events being triggered by a single device. The latter situation could lead to location ambiguity and could reduce the accuracy of travel time estimation. Therefore, the accuracy of travel time estimation by Bluetooth technology depends on how location ambiguity is handled by the estimation method. The issue of multiple Detection events in the context of travel time estimation by Bluetooth technology has been considered by various researchers. However, treatment of this issue has been simplistic. Most previous studies have used the first Detection event (enter enter) as the best estimate. No systematic analysis has been conducted to explore the most accurate method of travel time estimation with multiple Detection events. In this study, different aspects of the Bluetooth Detection Zone, including size and impact on the accuracy of travel time estimation, were discussed. Four methods were applied to estimate travel time: enter enter, leave leave, peak peak, and combined. These methods were developed on the basis of various technical considerations related to multiple Detection events. A controlled field experiment was conducted to evaluate the accuracy of the methods through comparison with the ground truth travel time data measured by Global Positioning System technology. The results showed that the accuracy of the combined and peak peak methods was higher than that of the other methods and that the employment of the first Detection event did not necessarily yield the best travel time estimation.
Jonas Hammershoj Olesen - One of the best experts on this subject based on the ideXlab platform.
-
Reliability of Bluetooth Technology for Travel Time Estimation
Journal of Intelligent Transportation Systems, 2014Co-Authors: Bahar Namaki Araghi, Rajesh Krishnan, L.t. Christensen, Jonas Hammershoj Olesen, Harry LahrmannAbstract:A unique Bluetooth-enabled device may be detected several times or not at all when it passes a sensor location. This depends mainly on the strength and speed of a transmitting device, discovery procedure, location of the device relative to the Bluetooth sensor, the Bluetooth sensor's ping cycle (0.1 s), the size and shape of the sensor's Detection Zone, and the time span for which the Bluetooth-enabled device is within the Detection Zone. The influences of size of Bluetooth sensor Detection Zones and Bluetooth discovery procedure on multiple Detection events have been mentioned in previous research. However, their corresponding impacts on accuracy and reliability of estimated travel time have not been evaluated. In this study, a controlled field experiment is conducted to collect both Bluetooth and global positioning system (GPS) data for 1000 trips to be used as the basis for evaluation. Data obtained by GPS logger are used to calculate actual travel time, referred to as ground truth, and to geo-code the...
-
Use of low-level sensor data to improve the accuracy of bluetooth-based travel time estimation
Transportation Research Record, 2013Co-Authors: Bahar Namaki Araghi, L.t. Christensen, Jonas Hammershoj Olesen, R. Krishnan, Harry LahrmannAbstract:Bluetooth sensors have a large Detection Zone compared with other static vehicle reidentification systems. A larger Detection Zone increases the probability of detecting a Bluetooth-enabled device in a fast-moving vehicle, yet increases the probability of multiple Detection events being triggered by a single device. The latter situation could lead to location ambiguity and could reduce the accuracy of travel time estimation. Therefore, the accuracy of travel time estimation by Bluetooth technology depends on how location ambiguity is handled by the estimation method. The issue of multiple Detection events in the context of travel time estimation by Bluetooth technology has been considered by various researchers. However, treatment of this issue has been simplistic. Most previous studies have used the first Detection event (enter-enter) as the best estimate. No systematic analysis has been conducted to explore the most accurate method of travel time estimation with multiple Detection events. In this study, different aspects of the Bluetooth Detection Zone, including size and impact on the accuracy of travel time estimation, were discussed. Four methods were applied to estimate travel time: enter-enter, leave-leave, peak-peak, and combined. These methods were developed on the basis of various technical considerations related to multiple Detection events. A controlled field experiment was conducted to evaluate the accuracy of the methods through comparison with the ground truth travel time data measured by Global Positioning System technology. The results showed that the accuracy of the combined and peak-peak methods was higher than that of the other methods and that the employment of the first Detection event did not necessarily yield the best travel time estimation.
-
Use of {Low}-{Level} {Sensor} {Data} to {Improve} the {Accuracy} of {Bluetooth}-{Based} {Travel} {Time} {Estimation}
Transportation Research Record, 2013Co-Authors: Bahar Namaki Araghi, Rajesh Krishnan, L.t. Christensen, Jonas Hammershoj Olesen, Harry LahrmannAbstract:Bluetooth sensors have a large Detection Zone compared with other static vehicle reidentification systems. A larger Detection Zone increases the probability of detecting a Bluetooth-enabled device in a fast-moving vehicle, yet increases the probability of multiple Detection events being triggered by a single device. The latter situation could lead to location ambiguity and could reduce the accuracy of travel time estimation. Therefore, the accuracy of travel time estimation by Bluetooth technology depends on how location ambiguity is handled by the estimation method. The issue of multiple Detection events in the context of travel time estimation by Bluetooth technology has been considered by various researchers. However, treatment of this issue has been simplistic. Most previous studies have used the first Detection event (enter enter) as the best estimate. No systematic analysis has been conducted to explore the most accurate method of travel time estimation with multiple Detection events. In this study, different aspects of the Bluetooth Detection Zone, including size and impact on the accuracy of travel time estimation, were discussed. Four methods were applied to estimate travel time: enter enter, leave leave, peak peak, and combined. These methods were developed on the basis of various technical considerations related to multiple Detection events. A controlled field experiment was conducted to evaluate the accuracy of the methods through comparison with the ground truth travel time data measured by Global Positioning System technology. The results showed that the accuracy of the combined and peak peak methods was higher than that of the other methods and that the employment of the first Detection event did not necessarily yield the best travel time estimation.
Rajesh Krishnan - One of the best experts on this subject based on the ideXlab platform.
-
Reliability of Bluetooth Technology for Travel Time Estimation
Journal of Intelligent Transportation Systems: Technology Planning and Operations, 2015Co-Authors: Bahar Namaki Araghi, Rajesh Krishnan, Jonas Hammershøj Olesen, Lars Tørholm Christensen, Harry LahrmannAbstract:Abstract A unique Bluetooth-enabled device may be detected several times or not at all when it passes a sensor location. This depends mainly on the strength and speed of a transmitting device, discovery procedure, location of the device relative to the Bluetooth sensor, the Bluetooth sensor's ping cycle (0.1 seconds), the size and shape of the sensor's Detection Zone, and the time span that the Bluetooth-enabled device is within the Detection Zone. The influences of size of Bluetooth sensor Detection Zones and Bluetooth discovery procedure on multiple Detection events have been mentioned in previous research. However, their corresponding impacts on accuracy and reliability of estimated travel time have not been evaluated. In this study, a controlled field experiment is conducted to collect both Bluetooth and GPS data for 1000 trips to be used as the basis for evaluation. Data obtained by GPS logger is used to calculate actual travel time, referred to as ground truth, and to geo-code the Bluetooth Detection events. In this setting, reliability is defined as the percentage of devices captured per trip during the experiment. It is found that, on average, Bluetooth-enabled devices will be detected 80% of the time while passing a sensor location. The impact of location ambiguity caused by size of Detection Zone is evaluated using geo-coded Bluetooth data. Results show that more than 80% of the Detection events are recorded within the range of 100 meters from the sensor centre line. It is also shown that short-range antennae detect Bluetooth-enabled devices in a closer location to the sensor, thus providing a more accurate travel time estimate. However, the smaller the size of the Detection Zone, the lower the penetration rate, which could itself influence the accuracy of estimates. Therefore, there has to be a trade-off between acceptable level of location ambiguity and penetration rate for configuration and coverage of the antennae.\nAbstract A unique Bluetooth-enabled device may be detected several times or not at all when it passes a sensor location. This depends mainly on the strength and speed of a transmitting device, discovery procedure, location of the device relative to the Bluetooth sensor, the Bluetooth sensor's ping cycle (0.1 seconds), the size and shape of the sensor's Detection Zone, and the time span that the Bluetooth-enabled device is within the Detection Zone. The influences of size of Bluetooth sensor Detection Zones and Bluetooth discovery procedure on multiple Detection events have been mentioned in previous research. However, their corresponding impacts on accuracy and reliability of estimated travel time have not been evaluated. In this study, a controlled field experiment is conducted to collect both Bluetooth and GPS data for 1000 trips to be used as the basis for evaluation. Data obtained by GPS logger is used to calculate actual travel time, referred to as ground truth, and to geo-code the Bluetooth Detection events. In this setting, reliability is defined as the percentage of devices captured per trip during the experiment. It is found that, on average, Bluetooth-enabled devices will be detected 80% of the time while passing a sensor location. The impact of location ambiguity caused by size of Detection Zone is evaluated using geo-coded Bluetooth data. Results show that more than 80% of the Detection events are recorded within the range of 100 meters from the sensor centre line. It is also shown that short-range antennae detect Bluetooth-enabled devices in a closer location to the sensor, thus providing a more accurate travel time estimate. However, the smaller the size of the Detection Zone, the lower the penetration rate, which could itself influence the accuracy of estimates. Therefore, there has to be a trade-off between acceptable level of location ambiguity and penetration rate for configuration and coverage of the antennae.
-
Reliability of Bluetooth Technology for Travel Time Estimation
Journal of Intelligent Transportation Systems, 2014Co-Authors: Bahar Namaki Araghi, Rajesh Krishnan, L.t. Christensen, Jonas Hammershoj Olesen, Harry LahrmannAbstract:A unique Bluetooth-enabled device may be detected several times or not at all when it passes a sensor location. This depends mainly on the strength and speed of a transmitting device, discovery procedure, location of the device relative to the Bluetooth sensor, the Bluetooth sensor's ping cycle (0.1 s), the size and shape of the sensor's Detection Zone, and the time span for which the Bluetooth-enabled device is within the Detection Zone. The influences of size of Bluetooth sensor Detection Zones and Bluetooth discovery procedure on multiple Detection events have been mentioned in previous research. However, their corresponding impacts on accuracy and reliability of estimated travel time have not been evaluated. In this study, a controlled field experiment is conducted to collect both Bluetooth and global positioning system (GPS) data for 1000 trips to be used as the basis for evaluation. Data obtained by GPS logger are used to calculate actual travel time, referred to as ground truth, and to geo-code the...
-
Use of {Low}-{Level} {Sensor} {Data} to {Improve} the {Accuracy} of {Bluetooth}-{Based} {Travel} {Time} {Estimation}
Transportation Research Record, 2013Co-Authors: Bahar Namaki Araghi, Rajesh Krishnan, L.t. Christensen, Jonas Hammershoj Olesen, Harry LahrmannAbstract:Bluetooth sensors have a large Detection Zone compared with other static vehicle reidentification systems. A larger Detection Zone increases the probability of detecting a Bluetooth-enabled device in a fast-moving vehicle, yet increases the probability of multiple Detection events being triggered by a single device. The latter situation could lead to location ambiguity and could reduce the accuracy of travel time estimation. Therefore, the accuracy of travel time estimation by Bluetooth technology depends on how location ambiguity is handled by the estimation method. The issue of multiple Detection events in the context of travel time estimation by Bluetooth technology has been considered by various researchers. However, treatment of this issue has been simplistic. Most previous studies have used the first Detection event (enter enter) as the best estimate. No systematic analysis has been conducted to explore the most accurate method of travel time estimation with multiple Detection events. In this study, different aspects of the Bluetooth Detection Zone, including size and impact on the accuracy of travel time estimation, were discussed. Four methods were applied to estimate travel time: enter enter, leave leave, peak peak, and combined. These methods were developed on the basis of various technical considerations related to multiple Detection events. A controlled field experiment was conducted to evaluate the accuracy of the methods through comparison with the ground truth travel time data measured by Global Positioning System technology. The results showed that the accuracy of the combined and peak peak methods was higher than that of the other methods and that the employment of the first Detection event did not necessarily yield the best travel time estimation.