Bertrand Merminod

High-precision satellite positioning system as a new tool to study the biomechanics of human locomotion.

New Global Positioning System (GPS) receivers allow now to measure a location on earth at high frequency (5Hz) with a centimetric precision using phase differential positioning method. We studied whether such technique was accurate enough to retrieve basic parameters of human locomotion. Eight subjects walked on an athletics track at four different imposed step frequencies (70-130steps/min) plus a run at free pace. Differential carrier phase localization between a fixed base station and the mobile antenna mounted on the walking person was calculated. In parallel, a triaxial accelerometer, attached to the low back, recorded body accelerations. The different parameters were averaged for 150 consecutive steps of each run for each subject (total of 6000 steps analyzed). We observed a perfect correlation between average step duration measured by accelerometer and by GPS (r=0.9998, N=40). Two important parameters for the calculation of the external work of walking were also analyzed, namely the vertical lift of the trunk and the velocity variation per step. For an average walking speed of 4.0km/h, average vertical lift and velocity variation were, respectively, 4.8cm and 0.60km/h. The average intra-individual step-to-step variability at a constant speed, which includes GPS errors and the biological gait style variation, were found to be 24. 5% (coefficient of variation) for vertical lift and 44.5% for velocity variation. It is concluded that GPS technique can provide useful biomechanical parameters for the analysis of an unlimited number of strides in an unconstrained free-living environment.

Measurement of the mechanical power of walking by satellite positioning system (GPS).

PURPOSE This descriptive article illustrates the application of Global Positioning System (GPS) professional receivers in the field of locomotion studies. The technological challenge was to assess the external mechanical work in outdoor walking. METHODS Five subjects walked five times during 5 min on an athletic track at different imposed stride frequency (from 70-130 steps x min(-1)). A differential GPS system (carrier phase analysis) measured the variation of the position of the trunk at 5 Hz. A portable indirect calorimeter recorded breath-by-breath energy expenditure. RESULTS For a walking speed of 1.05 +/- 0.11 m x s(-1), the vertical lift of the trunk (43 +/- 14 mm) induced a power of 46.0 +/- 20.4 W. The average speed variation per step (0.15 +/- 0.03 m x s(-1)) produced a kinetic power of 16.9 +/- 7.2 W. As compared with commonly admitted values, the energy exchange (recovery) between the two energy components was low (39.1 +/- 10.0%), which induced an overestimated mechanical power (38.9 +/- 18.3 W or 0.60 W x kg(-1) body mass) and a high net mechanical efficiency (26.9 +/- 5.8%). CONCLUSION We assumed that the cause of the overestimation was an unwanted oscillation of the GPS antenna. It is concluded that GPS (in phase mode) is now able to record small body movements during human locomotion, and constitutes a promising tool for gait analysis of outdoor unrestrained walking. However, the design of the receiver and the antenna must be adapted to human experiments and a thorough validation study remains to be conducted.

UWB and MEMS Based Indoor Navigation

Thanks to its physical characteristics, Ultra-wideband (UWB) is one of the most promising technologies for indoor pedestrian navigation. UWB radio localisation systems however experience multipath phenomena that decrease the precision and the reliability of the users location. To cope with complex indoor environments, UWB radio signals are coupled with inertial measurements from Micro Electro Mechanical Sensors (MEMS) in an extended Kalman filter. Improved performances of the filter are presented and compared with reference trajectories and with pure inertial solutions. Only specific selection methods enable this improvement by detecting and removing outliers in the raw localisation data.

On foot navigation : When GPS alone is not enough

Integration of GPS/INS navigation systems is a common topic for aeronautical and road applications. The use of these technologies for personal localisation requires more than just portable sensors and a change of ergonomics; it requires a totally different approach for dead reckoning algorithms. This paper will focus on different human applications and reveals the particular problem encountered.

Improving pedestrian dynamics modelling using fuzzy logic

The complementary nature of MEMS based pedestrian dead-reckoning (PDR) navigation and GNSS (Global Navigation Satellite System) has long been recognized. The advantages are quite clear for those applications requiring indoor positioning and that, for one reason or another, cannot rely on short-range infrastructure-based positioning systems (e.g. WiFi, UWB) to cope with the lack of availability of GNSS indoors. One such example of application is firemen coordination during emergency interventions.

Direct Georeferencing of a Pushbroom, Lightweight Hyperspectral System for Mini-UAV Applications

Hyperspectral imagery has proven its potential in many research applications, especially in the field of environmental sciences. Currently, hyperspectral imaging is generally performed by satellite or aircraft platforms, but mini-UAV (Unmanned Aerial Vehicle) platforms (<20 kg) are now emerging. On such platforms, payload restrictions are critical, so sensors must be selected according to stringent specifications. This article presents the integration of a light pushbroom hyperspectral sensor onboard a multirotor UAV, which we have called Hyper-DRELIO (Hyperspectral DRone for Environmental and LIttoral Observations). This article depicts the system design: the UAV platform, the imaging module, the navigation module, and the interfacing between the different elements. Pushbroom sensors offer a better combination of spatial and spectral resolution than full-frame cameras. Nevertheless, data georectification has to be performed line by line, the quality of direct georeferencing being limited by mechanical stability, good timing accuracy, and the resolution and accuracy of the proprioceptive sensors. A georegistration procedure is proposed for geometrical pre-processing of hyperspectral data. The specifications of Hyper-DRELIO surveys are described through two examples of surveys above coastal or inland waters, with different flight altitudes. This system can collect hyperspectral data in VNIR (Visible and Near InfraRed) domain above small study sites (up to about 4 ha) with both high spatial resolution (<10 cm) and high spectral resolution (1.85 nm) and with georectification accuracy on the order of 1 to 2 m.

Leman-Baikal: Remote sensing of lakes using an ultralight plane

The Leman-Baikal project constitutes an international Swiss-Russian collaborative research initiative in the field of physical limnology. The three-year framework involves the development and deployment of a novel multispectral and hyperspectral remote sensing platform optimised for the sensing of land and water surfaces from an ultralight aircraft. In this paper we discuss the developed remote sensing methodology and the initial obtained results.

Icy lakes extraction and water-ice classification using Landsat 8 OLI multispectral data

ABSTRACT We present an algorithm discriminating ice from open water on icy lakes using multispectral data from Landsat 8. Lakes are first extracted from the images using a new radiometric index coined ILI (Icy Lakes Index) which uses the stability of the reflectance of water and ice in the shortwave infrared bands. Quantitative comparisons to state-of-the-art indexes such as the Modified Normalised Difference Water Index (MNDWI) or the Water Ratio Index (WRI) show the ILI separates mixed ice/water bodies from land better than the current indexes, consistently achieving kappa coefficients () above 0.93 with manually labelled reference data. Additionally, these results suggest that the ILI has a very high optimal threshold stability, compared to other indexes. In the delineated lake area, we perform a supervised classification with a decision tree using radiometric properties, but also texture properties such as the local standard deviations and average gradients in each band. A key feature of this classification is the Water-Ice Classification Index (WICI), also texture-based, which discriminates shallow water from ice efficiently. We prove the robustness of our classification algorithm by comparing its results to manually digitised reference data, but also to concurrent Sentinel-1 Synthetic Aperture Radar (SAR) data in the case of Lake Ladoga. In both cases, the comparison leads to ranging from 0.84 to 0.97.

Linking a rural sanctuary with ancient metallurgy at Kataliondas Kourvellos (Cyprus)

Kataliondas Kourvellos is located at the base of an unusual rock knob, in the lower Troodos foothills, about 20 kilometers south of Nicosia. Recent excavations by the University of Geneva revealed that the site was occupied both in the Pre-Pottery Neolithic period, at the end of the 8 th millennium BCE, and in the Cypro-Classical period, in the 4 th century BCE. During the Cypro-Classical period, the site seems to have functioned as a rural sanctuary, but the purpose of its location there is not clear: among other explanations, one could be its link with the mining, smelting, and/or trade of metal resources (the lower Troodos foothills have been exploited since the Bronze Age for their copper and other mineralogical resources).

Welcome to Switzerland

On behalf of the Swiss Institute of Navigation (ION-CH) and the Ecole Polytechnique de Lausanne (EPFL), the pleasure is mine to welcome each of you to the European Navigation Conference. Organised annually under the umbrella of the European Group of Institutes of Navigation (EUGIN), ENC 2017 is the twenty-fifth conference in the series, and the second one in Switzerland following Geneva in 2007.