Volume 4, Issue 2

Paragliding is unpowered flight in which pilots rely on their ability to navigate rising currents of air to remain airborne. Paraglider flight performance is an important measure of the capabilities of a particular design of a canopy. Most often, the performance characteristics of a canopy are measured as horizontal velocity vs. vertical velocity for steady state flight in still air. The performance curve created using this approach neglects to take into account the effect which turning has on flight. In contrast, the performance surface created from the research carried out in this paper demonstrates the effect of turning on canopy flight; such a representation of performance is novel to the authors' knowledge. To produce this surface, a flight was conducted in which a paraglider's performance was measured for various steady state velocities and turning rates; the data were then analyzed utilizing mathematical optimization after appropriate calibration corrections were applied.

Mainly in the context of global climate change the awareness of landslide hazards has risen considerably in most mountainous regions worldwide in the last years. National and regional hazard mapping programs were set up in many countries and most of the potentially endangered sites have been identified. Although exclusive geodetic and geotechnical instrumentation is available today, due to some economical reasons only few of the identified potentially risky landslides are monitored permanently. The intention of the alpEWAS research project is to develop and to test new techniques suitable for efficient and cost-effective landslide monitoring. These techniques are combined in a geo sensor network with an enclosed geo data base and a developed software package to use the whole system for stakeholder information and early warning purposes. The core of the project is the development and testing of the three innovative measurement systems time domain reflectometry (TDR) for the detection of subsurface displacements in boreholes and reflectorless video tacheometry (VTPS) and a low cost GNSS sensor component for the determination of 3D surface movements. Essential experiences obtained during the project will be described.

Three hydrostatic displacement monitoring system applications in Switzerland are discussed; the first concerns experience gained monitoring the foundation of the Albigna dam, the second relating to the underground stability of the Swiss Light Source synchrotron and the third concerning the deformation of a bridge near the city of Lucerne. Two different principles were applied, the Hydrostatic Levelling System (HLS) using the “half-filled pipe principle” developed by the Paul Scherrer Institute and the Large Area Settlement System (LAS) using the “differential pressure principle”. With both systems ground deformations induced by tidal forces can be seen. However, high accuracy of single sensors is not sufficient. A well-designed configuration of the complete system is equally important. On the other hand there are also limits imposed by installation logistics and by the environmental conditions. An example is the bridge monitoring application, where the acceleration along the bridge due to the passage of heavy trucks limits the feasibility of using hydrostatic levelling measurements.

It is necessary to use different sensors in an integrated manner – GPS, accelerometer, inclination sensor and so on – in order to monitor and identify static, quasi-static and resonant response of tall buildings subjected to wind loading. There are some differences among these sensors with respect to data sampling rate, data quality, and their measurement accuracy. Therefore, using different sensors together for a monitoring project is important because of the complementary nature of each sensor. In this study, the behaviour of a tall reinforced concrete building (30 stories high) under wind load has been monitored using GPS and inclination sensors. This paper assesses the dynamic measurement quality and reliability of inclinometers for building monitoring applications, and discusses the strengths and weaknesses of GPS vis-a-vis the use of inclination sensors for monitoring the dynamic response of tall buildings under wind load. Data collected by these sensors have been analysed in the time and frequency domains. It was found that GPS observations were distorted by multipath caused by a reflecting surface on top of the building. From the analyses in the frequency domain, the 1 st mode natural frequencies of the building determined from both sensors agree very well with each other. The discrepancy of this measured 1 st mode natural frequency compared to that derived from FEM (Finite Element Model) prediction is 7%.