Institut Geographique National Research Articles

Anomaly analysis of 18 years of newly merged GPS ephemeris from four IGS data centers

The merged GPS navigation files from the International GNSS Service (IGS) data centers, i.e., the Crustal Dynamics Data Information System (CDDIS), the Bundesamt fur Kartographie und Geodasie (BKG), the Scripps Institution of Oceanography (SIO), and the Institut Geographique National (IGN) are occasionally contaminated by anomalies and inconsistent user range accuracy (URA). This contamination impairs the performance assessment of GPS service, especially the system integrity. We remerged these files starting Day of Year (DOY) 1, 2000 using all available navigation data files from IGS stations. To effectively get the upper bound URA, a frequency-dependent pattern recognition method was developed. In addition, a comprehensive comparison between the navigation data remerged by us and those provided by the four IGS data centers was performed. The compared results revealed that TGD and Issue of Data Clock (IODC) were the dominating anomalies in the merged navigation data from CDDIS and SIO for the first several years after 2000, and M0, Ω0, ω, and af0 were the dominant anomalies in the merged data from IGN. In addition to a number of missing records, many records with incorrect PRN (pseudo-random noise number), identifying a GPS satellite, were found in files from the IGS data centers. Although the number of anomalies in the merged files from CDDIS has continued to decrease in recent years, they have not disappeared and would affect system-level assessment and scientific applications to a certain extent. The results also revealed that our remerged files were more complete, clean, compact and consistent, making them more suitable for GPS system performance assessment and related research studies. Moreover, those data are now openly available.

Use of Airborne LIDAR Bathymetry for Coastal Hydrographic Surveying: The French Experience

Abstract Starting in 2005, the French Naval Hydrographic and Oceanographic Office (Service Hydrographique et Oceanographique de la Marine [SHOM]) and the French National Geographic Institute (Institut Geographique National [IGN]) began conducting a series of coastal surveys using airborne light detection and ranging (LIDAR) bathymetry (ALB) and topographic LIDAR technologies. This paper describes SHOM's experience using ALB in very shallow coastal waters and under challenging hydrographic survey conditions. The performance of ALB in comparison to multibeam echosounder (MBES) and topographic LIDAR surveys is discussed. Further, a procedure is described for integrating ALB data sets from SHOM with topographic data sets from IGN. Recommendations on conducting future survey operations are provided in this paper based on the experience gained and lessons learned. Based on these experiences, SHOM and IGN have begun a national survey project on mapping the coastal areas (sea and land) of France.

Direction Estimation Using Square Lattice and Cadastral Map Assembling

This paper proposes a technique for direction estimation by means of square grid points in order to improve the performance of cadastral map assembling technique based on Merlin-Farber (MF) algorithm. The MF algorithm requires direction normalization of the segments (of cadastral map) preceding the assembling. Proposed direction estimation technique is based on the spatial frequency analysis of autocorrelation by MF algorithm for the square grid points regularly drawn with constant intervals on the segments. Since many square grid points are drawn over entire area of the segments the direction can be estimated more accurately with those points when compared the direction is estimated with single north arrow. To assemble two adjacent segments the longest common boundary is detected by MF algorithm. Evaluation experiments are performed to compare the accuracy and the success rate of map assembling when the direction is estimated and normalized based on the square grid points and when estimated and normalized based on the north arrow. Total of 324 map segments of 47 district provided by Institut Geographique National France are used in the experiments. While the map assembling based on the north arrow tends to form inaccurate cadastral maps the proposed technique assembles the map more accurately. The results of experiments shows that the proposed technique achieves sufficient success rate and accuracy so that it effectively reduces the labor cost and time of the cadastral map assembling.

A new statistical approach to extreme wind speeds in France

To analyze all wind data available in the French meteorological stations, to elaborate a new extreme wind speeds map, an homogenization tool is developed that allow the detection and the correction of breaks due to sensor change and modification of measurement environment. Breaks are detected on annual mean wind speed series. Daily maximal wind speed values for about 150 wind speed stations have been selected using this method. The meteorological station environment influence is corrected with the help of the Danish software WAsP that takes into account the relief, the roughness of the land within a radius of 5 km as well as the near wakes in a radius of 500 m. The relief is described by the numeric model of terrain of Institut Geographique National (IGN) on a 50 m grid step and the roughness of the land, by an interpretation of the database CORINE land cover by the Geographic Information System software MapInfo, coupled with a description of environment of each station by Météo-France. The time series of the maximal daily mean wind speed built from the maximal daily peak velocity are analyzed by the method of independent storms, first proposed by Cook [1982. Towards better estimation of extreme winds. J. Wind Eng. Ind. Aerodyn. 9, 295–323] already applied for UK by Miller et al. [2001. Towards a revised base wind speed map for the United Kingdom. Wind Struct. 4(3), 197–212]. The normalized mean wind speed of 50 years return period irrespective of wind direction is obtained for each meteorological station, by fitting the cumulative distribution by a Pareto law.

Analysis of a possible future degradation in the DORIS geodetic results related to changes in the satellite constellation

Recently, several improvements were made in the DORIS data processing at the IGN/JPL (Institut Geographique National, France; Jet Propulsion Laboratory, California Institute of Technology, USA) analysis center: use of GRACE-derived gravity fields, data preprocessing and station discontinuity detection, etc. This allowed enhanced performances for ground station geodetic positioning (typically 10 mm using a week of data), as well as for polar motion (0.5–1.0 mass for daily determination). However, since the loss in 2004 of the DORIS receiver on the TOPEX/Poseidon mission, only four satellites (SPOT-2, SPOT-4, SPOT-5, and ENVISAT) are currently equipped with DORIS receivers. Furthermore, most of them are aging and some have already far exceeded their expected lifetime. The goal of this paper is to analyze how the geodetic performances could be degraded in the future if one or more of these satellites would unfortunately be lost, and to envisage which satellites are currently the most critical in the DORIS geodetic performances. We have reanalyzed 1 year of recent DORIS data (2005), processing all possible combinations of satellite constellation sub-sets. We then compared these results (station coordinates and polar motion) with those obtained in regular data processing when using DORIS data from all four available satellites in 2005. We demonstrate the importance of the SPOT-5 data, equipped with a new type of on-board DORIS receiver. The study also shows some possible weaknesses in our current ENVISAT orbit computations. Fortunately, new DORIS satellites are also expected in the near future (Jason-2, CRYOSAT-2 and AltiKa), which could improve current DORIS-derived geodetic results due to their specific type of orbit (different from the SPOT sun-synchronous orbits) and also to enhanced on-board receivers.

Twenty years of evolution for the DORIS permanent network: from its initial deployment to its renovation

The ground network is one of the major components of the DORIS system. Its deployment, managed by the French national mapping agency [Institut Geographique National, (IGN)], started in 1986 at a sustained pace that allowed it to reach 32 stations upon the launch of the first DORIS-equipped satellite (SPOT-2) in 1990. For the first generation of transmitting antennas, the installation procedures were adapted to the decimetre performance objective for the DORIS system. During the second era of the deployment of an even denser network, the antenna support layouts gradually evolved towards a better quality, thus improving the long-term stability of the antenna reference point, and a new antenna model allowed a more accurate survey. As the positioning accuracy of the DORIS system improved, it was necessary to review the antenna stability for the whole network. A first stability estimation, using criteria like antenna model and support design, was followed by a major renovation effort which started in 2000 and is now almost complete. In 6 years, through the renovation or installation of 43 stations and the implementation of new installation procedures to meet more stringent stability requirements, significant improvement in network quality was achieved. Later a more analytical approach, taking into account the characteristics of each element that support the antenna, has been taken to assess the potential stability of all DORIS occupations. IGN is also in charge of its operational maintenance, an intensive activity on account of the significant failure rate of the successive generations of equipment. Nevertheless, thanks to its unique density and homogeneity, DORIS has maintained a very good coverage rate of the satellite orbits. Through 38 well-distributed current co-locations with the Global Positioning System, Satellite Laser Ranging and Very Long Baseline Interferometry techniques in its current 56-station network, DORIS contributes significantly to the realisation of the International Terrestrial Reference System. DORIS stations in areas where no other space geodesy technique is available provide a significant contribution to the study of plate tectonics. Many stations co-located with tide gauges contribute to the monitoring of sea level changes. Although it has several advantages over similar techniques, there is still room for improvement in the DORIS network.

First results of DORIS data analysis at Geodetic Observatory Pecný

In a cooperation between the Astronomical Institute, University of Bern (AIUB), the Geodetic Observatory Pecný (GOPE), and the Institut Geographique National (IGN), DORIS data analysis capabilities were implemented into a development version of the Bernese GPS software. The DORIS Doppler observables are reformulated such that they are similar to global navigation satellite system (GNSS) carrier-phase observations, allowing the use of the same observation models and algorithms as for GNSS carrier-phase data analysis with only minor software modifications. As such, the same algorithms may be used to process DORIS carrier-phase observations. First results from the analysis of 3 weeks of DORIS data (September 2004, five DORIS-equipped satellites) at GOPE are promising and are presented here. They include the comparison of station coordinates with coordinate estimates derived by the Laboratoire d’Etudes en Geophysique et Oceanographie Spatiale/Collecte Localisation Satellites analysis centre (LCA) and the Institut Geographique National/Jet Propulsion Laboratory (IGN/JPL), and the comparison of Earth orientation parameters (EOPs) with the International Earth Rotation and Reference Frames Service (IERS) C04 model. The modified Bernese results are of a slightly lower, but comparable, quality than corresponding solutions routinely computed within the IDS (International DORIS Service). The weekly coordinate repeatability RMS is of the order of 2–3 cm for each 3D station coordinate. Comparison with corresponding estimates of station coordinates from current IDS analysis centers demonstrates similar precision. Daily pole component estimates show a mean difference from IERS-C04 of 0.6 mas in Xp and − 0.5 mas in Yp and a RMS of 0.8 mas in Xp and 0.9 mas in Yp(mean removed). An automatic analysis procedure is under development at GOPE, and routine DORIS data processing will be implemented in the near future.

Ionospheric applications of the scintillation and tomography receiver in space (CITRIS) mission when used with the DORIS radio beacon network

The scintillation and tomography receiver in space (CITRIS) instrument will orbit the Earth near 560 km altitude to detect signals from the ground-based array of more than 50 DORIS UHF/S-band radio beacons established at sites around the world by the French Centre National d‘Etudes Spatiales (CNES) and the Institut Geographique National (IGN). The CITRIS receiver is on the US Air Force Space Test Program satellite STPSAT1, which is scheduled for launch in November 2006. CITRIS will record ionospheric total electron content (TEC) and radio scintillations with a unique ground-to-space geometry. The new instrument has been developed to study the ionosphere using data obtained with the UHF and S-band radio transmissions from the DORIS beacons because ionospheric radio scintillations can seriously degrade the performance of many space-geodetic systems, including the DORIS precise satellite orbitography system and GNSS (Global Navigation Satellite Systems). The ionospheric data will be based on radio signals sampled at a rate of 200 Hz by the CITRIS receiver. Numerical models have been used to predict that the DORIS signals measured by CITRIS may have 30 dB fluctuations in amplitude and 30 rad in phase as the satellite flies over kilometer-scale ionospheric structures. The data from the space-based CITRIS receiver will help update and validate theories on the generation and effect of ionospheric irregularities known to influence radio systems. By using simultaneous beacon transmissions from DORIS on the ground and from low-Earth-orbit beacons in space, the concept of reciprocity in a non-bilateral propagation medium like the ionosphere will be tested. Computer simulations are used to predict the magnitude of amplitude and phase scintillations that are expected to be recorded with the CITRIS instrument.

Deformation actuelle de la chaine de Belledonne (massifs cristallins externes alpins, France); comparaison triangulation historique-GPS

Deformation actuelle de la chaine de Belledonne (massifs cristallins externes alpins, France); comparaison triangulation historique-GPS

Contextual Building Typification in Automated Map Generalization

Cartographic generalization aims to represent geographical information on a map whose specifications are different from those of the original database. Generalization often implies scale reduction, which generates legibility problems. To be readable at smaller scale, geographical objects often need to be enlarged, which generates problems of overlapping features or map congestion. To manage this problem with respect to buildings, we present a method of selection based on the typification principle that creates a result with fewer objects, but preserves the initial pattern of distribution. For this we use a graph of proximity on the building set, which is analysed and segmented with respect to various criteria, taken from gestalt theory. This analysis provides geographical information that is attached to each group of buildings such as the mean size of buildings, shape of the group, and density. This information is independent of scale. The information from the analysis stage is used to define methods to represent them at the target scale. The aim is to preserve the pattern as far as possible, preserve similarities and differences between the groups with regard to density, size and orientation of buildings. We present some results that have been obtained using the platform Stratege, developed in the COGIT laboratory at the Institut Geographique National, Paris.

Aurignacian Settlement Patterns in the Vézère Valley

Etude de la mobilite des groupes aurignaciens du bassin de la Vezere a partir de l'economie de la matiere premiere lithique et de la saisonnalite animale. Ces elements fournissent des donnees nouvelles sur l'extension du territoire exploite, sur le degre de sedentarisation et de saisonnalite humaine

Aurignacian Settlement Patterns in the Vézère Valley

Aurignacian Settlement Patterns in the Vézère Valley

Study of a wide-angle laser ranging system for relative positioning of ground-based benchmarks with millimeter accuracy

A wide-angle airborne laser ranging system (WA-ALRS) is developed at the Institut Geographique National (IGN), France, with the aim of providing a new geodesy technique devoted to large (100 km2) networks with a high density (1 km−2) of benchmarks. The main objective is to achieve a 1-mm accuracy in relative vertical coordinates from aircraft measurements lasting a few hours. This paper reviews the methodology and analyzes the first experimental data achieved from a specific ground-based experiment. The accuracy in relative coordinate estimates is studied with the help of numerical simulations. It is shown that strong accuracy limitations arise with a small laser beam divergence combined with short range measurements when relatively few simultaneous range data are produced. The accuracy is of a few cm in transverse coordinates and a few mm in radial coordinates. The results from ground-based experimental data are fairly compatible with these predictions. The use of a model for systematic errors in the vehicle trajectory is shown to be necessary to achieve such a high accuracy. This work yields the first complete validation of modelization and methodology of this technique. An accuracy better than 1 mm and a few mm in vertical and horizontal coordinates, respectively, is predicted for aircraft experiments.

Present-day deformation of the Dauphine Alpine and Subalpine massifs (SE France)

The positions of 20 geodetic points surveyed in 1946–1952 by the Institut Géographique National in the Grenoble area (western Alps) were remeasured in 1993–1994 using GPS. We evaluate the displacements of the common points of the networks between the two surveys, and calculate the strain-rate tensors for different sets of three adjacent points. The significant N70° shortening direction observed at the boundary of the Belledonne and Taillefer massifs suggests that the dextral strike-slip motion between the External Crystalline Massifs (ECM) and the Subalpine domain is still active. Geological evidence suggests that this deformation, which is compatible with the few focal mechanisms available for the area, occurred throughout the late Neogene. Our data also suggest a roughly 3–5 mm yr−1 active shortening concentrated at the external front of the Subalpine chains. This thrust motion results in a principal axis of compression orientated N130°, oblique to the direction of shortening observed in the ECM. This change in direction is also seen in in situ stress measurements. This motion may mark the southward continuation of the active fault observed in the Jura mountains by Jouanne, Ménard & Darmendrail (1995).

Satellite remote sensing in monitoring change of seabirds: use of Spot Image in king penguin population increase at Ile aux Cochons, Crozet Archipelago

The king penguin colony at Ile aux Cochons, Crozet Archipelago (southern Indian Ocean) is the largest in the world. The change in its surface area was investigated by means of satellite remote sensing using spot scene. The satellite picture enabled us to locate the colony and to determine that the surface area occupied by the colony has increased by 56% between 1962 and 1988. The increase in the surface area occupied by the colony was confirmed by a map realised in 1982 (by the Institut Geographique National). The high resolution system available on the spot system which allows at present at 10 m ground resolution, and 5 m in the near future, can thus be a useful tool for monitoring medium to long-term changes in marine bird populations breeding in colonies composed of birds spaced a constant distance from one another. Based on the surface area occupied by the colony and the published data on the population size on Possession Island, as well as information on the breeding frequency of the species, we estimated that the total breeding population is about 1,000,000 pairs for the whole archipelago and that about 70% of birds breed at Ile aux Cochons.

Computer‐Assisted Routing of Dangerous Goods for Haute‐Normandie

To assess the best routes for the transport of dangerous goods in an area of 600 km2 in France, software based on a geographical information system was developed to manage, treat, and represent statistical and geographical data related to the evaluation of the risk of transport on a road network. The probability of an accident and release is derived from the links in a digitized network, provided by the Institut Geographique National (IGN) on a 1/50,000 scale, according to the links' characteristics. The active, student and nonactive population figures are from the 1982 census, and are distributed among categorized (i.e., urban, industrial) areas of administrative units called communes. The intersection of this population layout with an impact zone leads to a measure of the people exposed to damage. An impact zone is a corridor along a road; the diameter of the zone depends upon the nature and quantity of dangerous materials that are being transported. Multiplication of the accident probability by the num...

Positioning results with doris on SPOT2 after first year of mission

A new space system named DORIS has been developed by the Centre National d'Etudes Spatiales in France with the collaboration of the Institut Geographique National for precise orbit determination and positioning. It is a Doppler‐based system with a worldwide ground network of transmitting beacons and an onboard receiver. The SPOT2 satellite launched in January 1990 carries DORIS as an experimental instrument. In this study, we present positioning results obtained from the analysis of the first 10 months of DORIS data through a semi‐dynamical approach (i.e. the satellite orbit is improved simultaneously with the beacon positions). External calibration with satellite laser ranging (SLR) and very long baseline interferometry (VLBI) positions indicates that DORIS accuracy from a few months of data is presently 15–20 cm rms in absolute and relative (baseline length > 1000 km) positioning. For very short baselines (< 100 km), external comparison with ground‐based geodetic measurements indicates a few cm accuracy. Month to month repeatability of both absolute and relative (baseline length > 1000 km) positioning results is in the range 10–20 cm rms. For the shortest baselines (< 100 km), the month to month repeatability is better than 5 cm in cartesian coordinates. This repeatability is only ∼ 2 cm in the north and east components whereas it is 12 cm in the vertical component, suggesting that tropospheric errors are important. It should be possible to improve these results in the future by reducing the residual orbit error, especially the atmospheric drag perturbation which was particularly troublesome in 1990, a year having very large solar activity and by improving modeling of the tropospheric correction.

Realization of the Primary Terrestrial Reference Frame

AbstractThe PTRF is based on 43 sites with 64 SSC collocation points with the optimum geographic distribution, which were selected from all stations of the ITRF89 according to the criterion of the minimum value of the errors of 7 parameters of transformation. The ITRF89 was computed by the IERS Terrestrial Frame Section in Institut Geographique National - IGN and contains 192 VLBI and SLR stations (points) with 119 collocation ones. The PTRF has been compared with the ITRF89. The errors of the 7 parameters of transformation between the PTRF and 18 individual SSC as well as the mean square errors of station coordinates are of the same order as those for the ITRF89. The transformation parameters between the ITRF89 and the PTRF are negligible and their errors are of the order of 3 mm.

TRAPU: a tool for data capture and visualisation of the urban fabric

The TRAPU system developed by the Institut Geographique National is a computer tool for the digitising and modelling of three-dimensional urban forms using photogrammetric techniques. The data structures employed allow the creation of convex polyhedra, laminae and lines in space. Topography of the ground surface may be represented by triangulated surfaces. Perspective and orthographic views can be created. Data can be exchanged with other CAD systems. Applications of the system so far have been mainly for visualising architectural projects in context, and for studying the impact of new roads and large urban developments.

Concepts and methods of the Central Bureau of the International Earth Rotation Service

The International Earth Rotation Service (IERS) was organized by the International Union of Geodesy and Geophysics and the International Astronomical Union. It started operation on 1988 January 1. Its responsabilities and activities are described in the Geodesist's Handbook (1988). The Central Bureau ofIERS is operated by a scientific team established in cooperation by Observatoire de Paris, Institut Geographique National and Bureau des Longitudes. This team was selected in 1987 on the basis of the present document which describes in some detail the concepts and methods for establishing and maintaining celestial and terrestrial reference frames for Earth orientation monitoring (polar motion, universal time, precession/nutation). The work of the Central Bureau is based on these concepts and methods, not withstanding future evolution made possible by the improvements in observations and theories.