Standard GPS Receiver Research Articles

Modeling and Improving the Energy Performance of GPS Receivers for Location Services

Integrated GPS receivers have become a basic module in today’s mobile devices. While serving as the cornerstone for location based services, GPS modules have a serious battery drain problem due to high computation load. This paper aims to reveal the impact of key software parameters on GPS energy consumption, by establishing an energy model for a standard GPS receiver architecture as found in both academic and industrial designs. In particular, our measurements show that the receiver’s energy consumption is in large part linear with the number of tracked satellites as well as the length of the raw GPS signal. This leads to an energy efficient design of selective tracking algorithm with large satellite Geometric Dilution of Precision (GDOP) weight, well spatial distribution, and large signal intensity. Real experimental results on three typical scenarios show that our selective tracking algorithm provides better tradeoff between positioning accuracy and energy consumption than standard GPS receivers.

A 10-Year Comparison of Water Levels Measured with a Geodetic GPS Receiver versus a Conventional Tide Gauge

AbstractA standard geodetic GPS receiver and a conventional Aquatrak tide gauge, collocated at Friday Harbor, Washington, are used to assess the quality of 10 years of water levels estimated from GPS sea surface reflections. The GPS results are improved by accounting for (tidal) motion of the reflecting sea surface and for signal propagation delay by the troposphere. The RMS error of individual GPS water level estimates is about 12 cm. Lower water levels are measured slightly more accurately than higher water levels. Forming daily mean sea levels reduces the RMS difference with the tide gauge data to approximately 2 cm. For monthly means, the RMS difference is 1.3 cm. The GPS elevations, of course, can be automatically placed into a well-defined terrestrial reference frame. Ocean tide coefficients, determined from both the GPS and tide gauge data, are in good agreement, with absolute differences below 1 cm for all constituents save K1 and S1. The latter constituent is especially anomalous, probably owing to daily temperature-induced errors in the Aquatrak tide gauge.

Cars as a Diffuse Network of Road-Environment Monitoring Nodes

The present paper aims to describe the conceptual idea to use cars as sensors to measure and acquire data related road environment. The parameters are collected using only standard equipment commonly installed and operative on commercial cars. Real sensors and car sub-systems (e.g. thermometers, accelerometers, ABS, ESP, and GPS) together with other “implicit” sensors (e.g. fog lights, windscreen wipers) acquire and contain information. They are shared inside an in-vehicle communication network using mainly the standard CAN bus and can be collected by a simple central node. This node can also be available on the market without too expensive costs thanks to some companies which business is devoted to car fleet monitoring. All the collected data are then geolocalized using a standard GPS receiver and sent to a remote elaboration unit, exploiting mobile network technologies such as GPRS or UMTS. A large number of cars, connected together in a diffuse Wireless Sensor Network, allow the elaboration unit to realize some info-layers put at the disposal of a car driver. Traffic, state of the road and other information about the weather can be received by car drivers using an ad hoc developed mobile application for smartphone which can give punctual information related to a specific route, previously set on the mobile phone navigator. The description of some experimental activities is presented, some technical points will be addressed and some examples of applications of the network of cars “as sensors” will be given.

Application of GPS for Sag Measurement of Overhead Power Transmission Line

Overhead conductor sag may be measured by different methods. In the paper measurement of sag of 66KV power transmission line under shut down conditions at no wind load using standard handheld GPS receiver BT 359 has done. The real time direct measurement of overhead conductor sag is needed for the operation of power transmission system. The measurement of conductor tension, temperature and ambient weather conditions are not required to monitor in this method. The digital signal processing (DSP) techniques is used to get better accuracy of GPS measurements. The Least Square Parameter Estimation (LSPE) method for the error estimation of GPS measurements is also incorporated.

PRECISE REAL-TIME POSITIONING WITH A LOW COST GPS ENGINE USING NEURAL NETWORKS

Position information obtained from standard GPS receivers has time variant errors. To make effective use of GPS information in a navigation system, it is essential to model these errors. In this paper, a new approach is presented for improvement of positioning accuracy using MLP, RBF, and RNN neural networks (NNs). The NNs estimate position errors that are used as Differential GPS (DGPS) corrections in real time positioning. Method validity is verified with experimental data from an actual data collection, before and after Selective Availability (SA) error. The result is a highly effective estimation technique for accurate positioning, so that positioning accuracy is drastically improved to less than 1.10 meters with SA on and 0.70 with SA off. The experimental tests results with real data emphasize that total performance of RNN is better than RBF and MLP considering trade off between accuracy and speed for DGPS corrections prediction.

Crossroads risk assessment using GPS and inter-vehicle communications

Recent developments in inter-vehicle communications (IVC) focus on the conception of suitable hardware and communications protocols. We contribute to this effort by analysing the performance of IVC through a vehicular application approach. The study aims to measure the contribution of IVC in comparison with traditional safety sensors on an advanced driver assistance scheme (ADAS) system. We choose to study the risk assessment in crossroads approaching. The system is based on a standard 802.11 technology combined to a standard low-cost GPS receiver. The performance is analysed regarding the application showing the feasibility of the system and its integration on board our prototype LARA.

Incorporation of neural network-like processors for GPS navigation

The solution for the receiver’s position and clock bias using four or more GPS pseudorange measurements involves nonlinear quadratic equations. One of the popular techniques for linearizing the equations and solving them is the least squares (LS) scheme based on an iterative gradient approach. For real-time applications when the solution is to be obtained within a time of the order of 100 ns, a computer often cannot comply with the desired computation time, or high-end computers are too expensive. In this paper various ordinary differential equation formulation schemes, and corresponding circuits of neuron-like analog processors, will be described and several tested in order to ascertain their suitability for GPS navigation processing purposes. The circuits of simple neuron-like analog processors are employed essentially for on-line inversion of matrices, which is usually required for determining LS solutions, as well as dilution of precision (DOP) calculation in standard GPS receivers. Data from single epoch and kinematic positioning experiments will be simulated to validate the effectiveness of the proposed scheme. The properties and performance of the proposed scheme will be assessed and compared to those of the conventional method of matrix inversion.