Driven by progress in sensor technology, computer methods and data processing capabilities, 3D laser scanning has found a wide range of new application fields in recent years. Particularly, monitoring the static and dynamic behaviour of large dams has always been a topic of great importance, due to the impact these structures have on the whole landscape where they are built. The main goal of this paper is to show the relevance and novelty of the laserscanning methodology developed, which incorporates different statistical and modelling approaches not considered until now. As a result, the methods proposed in this paper have provided the measurement and monitoring of the large “Las Cogotas” dam (Avila, Spain).

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A new approach for structural monitoring of large dams with a three-dimensional laser scanner

Global navigation satellite system (GNSS) ambiguity resolution is the process of resolving the unknown cycle ambiguities of the carrier phase data as integers. The sole purpose of ambiguity resolution is to use the integer ambiguity constraints as a means of improving significantly on the precision of the remaining GNSS model parameters. In this contribution, we consider the problem of ambiguity resolution for GNSS attitude determination. We analyse the performance of a new ambiguity resolution method for GNSS attitude determination. As it will be shown, this method provides a numerically efficient, highly reliable and robust solution of the nonlinearly constrained integer least-squares GNSS compass estimators. The analyses have been done by means of a unique set of extensive experimental tests, using simulated as well as actual GNSS data and using receivers of different manufacturers and type as well as different platforms. The executed field tests cover two static land experiments, one in the Netherlands and one in Australia, and two dynamic experiments, a low-dynamics vessel experiment and high-dynamics aircraft experiment. In our analyses, we focus on stand-alone, unaided, single-frequency, single-epoch attitude determination, as this is the most challenging case of GNSS compass processing.

/pdf/testing-of-a-new-single-frequency-gnss-carrier-phase-3r13phumny.pdf

Testing of a new single-frequency GNSS carrier phase attitude determination method: land, ship and aircraft experiments

A review of vertical motion heave compensation systems

New updated! The latest book from a very famous author finally comes out. Book of automatic extraction of man made objects from aerial and space images monte verita s, as an amazing reference becomes what you need to get. What's for is this book? Are you still thinking for what the book is? Well, this is what you probably will get. You should have made proper choices for your better life. Book, as a source that may involve the facts, opinion, literature, religion, and many others are the great friends to join with.

3rd International Workshop: Automatic Extraction of Man-Made Objects from Aerial and Space Images.

Errors in velocities and displacements deduced from accelerographs: An approach based on the theory of error propagation

Current research for multiple antenna GPS attitude determination is focused on obtaining high accuracy attitude using low cost receivers and low cost antennas. Measurements from low cost sensors typically suffer from factors such as increased measurement noise, multipath, antenna phase center variation and cycle slips. This paper describes the rapid development of a low cost attitude determination system for use on an Unmanned Aerial Vehicle (UAV) that will be used as in input for georeferencing an on-board camera. The filter was developed using a plug-and-play filter design that allows combinations of measurements and states to be easily implemented in an Extended Kalman Filter. Using such an approach has the significant advantage for integrated systems where, for example, attitude measurements can also be used as measurement updates to aid inertial navigation systems (INS) in a tight coupled architecture. An overview of the plug-and-play methodology is given along with a description of the constrained LAMBDA algorithm used for ambiguity determination.

Development of a Low Cost Multiple GPS Antenna Attitude System

In this work a system is proposed which will provide carrier phase accuracy positioning and two axis attitude measurements using only three low cost, single frequency, GPS receivers. Such a system will find application on platforms where minimal cost, weight and power consumption is critical; for example the mini-unmanned aerial vehicle (UAV). The six state measurements provided by the system may be used in the georeferencing of other sensor data or in the navigation of the platform itself. This contribution aims to increase the success rate of the integer ambiguity resolution process when positioning the platform by utilising knowledge of the double differenced integer ambiguities obtained in an attitude determination system. The robustness and 'time to solution' of the system will thus be improved. It is well known that the use of baseline length or geometry constraints in the attitude determination environment may significantly increase the integer ambiguity success rate, particularly where low cost, single frequency receivers are used. It has been shown that such constraints may increase the success rate to a level approaching 100%. Such constraints have been proven to allow the low cost GPS receiver to become an effective attitude determination system. In this work a two receiver attitude determination system is used with a third base receiver to provide both two axis attitude and position measurement. Knowledge of the double differenced integer ambiguities from the attitude determination system is used to reduce the number of candidates during the search for the integer ambiguities arising when the third receiver is included. When these ambiguities are resolved the unknown baselines between the roving (attitude) receivers and base receiver may be determined and the relative position obtained. The constraint in the positioning stage reduces the effect of uncorrelated errors between the two roving receivers. The benefits of this are observed primarily when using low quality receivers with considerable Gaussian noise exacerbated by exposure to highly dynamic environments. It is likely however that in most applications the baseline length between the two roving receivers will not allow the decorrelation of the multipath error and consequently this will still have a detrimental effect. Real world performance of the algorithm is examined by comparing the low cost system to a high grade Novatel SPAN integrated GPS/INS installed on a vehicle test bed. Tests are performed in an area with good sky view and within 3 km of the base station.

Precise kinematic positioning using single frequency GPS receivers and an integer ambiguity constraint

A version of this paper was presented at ENC-GNSS 2007, Geneva. Its reproduction was kindly authorised by the ENC-GNSS 07 Paper Selection Committee.The General Lighthouse Authorities of the UK & Ireland commissioned an assessment of the impact that the integration of Global Navigation Satellite Systems (GNSS) with Inertial Navigation Systems (INS) would have on the aids to navigation (AtoN) services currently provided, and those to be provided in the future. There is concern about the vulnerability of GNSS, and the provision of complementary and backup systems is seen to be of great importance. The integration of INS could provide an independent and self-contained navigation system, for a limited time period, invulnerable to external intentional or unintentional interference, or the influences of changes in national policies. The study included an analysis of the potential use of GNSS-INS in three of the four phases of a vessel's voyage: coastal, port approach and docking. The project consisted of a technology assessment, looking at the different inertial technologies that might be suitable for each phase. This was followed by a technology proving stage, evaluating suitable equipment using simulation and field trials to prove that the claimed performance could be achieved in practice. The final stage of the project was to assess the effects of the availability of such systems on existing and planned aids to navigation services.

The Potential Impact of GNSS/INS Integration on Maritime Navigation

It is well known that GPS measurements are regularly obstructed in urban environments. Positioning accuracy in such environments is significantly degraded and in many areas, it is not possible to obtain a GPS position fix at all. There are currently two methods that can be used to improve availability in the urban environment. Firstly, GPS receivers can be augmented with dead reckoning sensors such as an INS. Alternatively, High Sensitivity GPS (HSGPS) receivers can be used which are able to acquire and track very weak signals. This paper assesses the performance obtained from a GPS and low cost INS integrated system and a HSGPS receiver in an urban environment in Nottingham, UK. The navigation systems are compared to a high accuracy integrated GPS/INS system which is used to provide a reference trajectory. It is demonstrated that the differential GPS and low cost INS system can provide horizontal positioning accuracy of better than 2·5 m RMS in real-time, and better than 1 m RMS in post-processing, whereas the non-differential HSGPS receiver provides a real-time performance of 5 m RMS. These results were obtained in an environment where, with conventional GPS receivers, a position solution is only available 48·4% of the time. Operational considerations such as initial alignment of the GPS and low cost INS are also discussed when comparing the two systems for urban positioning applications.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0373463306003936

David Park

Papers

Development of a Low Cost Multiple GPS Antenna Attitude System

Precise kinematic positioning using single frequency GPS receivers and an integer ambiguity constraint

The Potential Impact of GNSS/INS Integration on Maritime Navigation

Low Cost, High Accuracy Positioning In Urban Environments

An Investigation in the Use of GPS and INS Sensors for Structural Health Monitoring