Wolfgang Niemeier

Evaluation of InSAR and TomoSAR for Monitoring Deformations Caused by Mining in a Mountainous Area with High Resolution Satellite-Based SAR

Interferometric Synthetic Aperture Radar (InSAR) and Differential Interferometric Synthetic Aperture Radar (DInSAR) have shown numerous applications for subsidence monitoring. In the past 10 years, the Persistent Scatterer InSAR (PSI) and Small BAseline Subset (SBAS) approaches were developed to overcome the problem of decorrelation and atmospheric effects, which are common in interferograms. However, DInSAR or PSI applications in rural areas, especially in mountainous regions, can be extremely challenging. In this study we have employed a combined technique, i.e., SBAS-DInSAR, to a mountainous area that is severely affected by mining activities. In addition, L-band (ALOS) and C-band (ENVISAT) data sets, 21 TerraSAR-X images provided by German Aerospace Center (DLR) with a high resolution have been used. In order to evaluate the ability of TerraSAR-X for mining monitoring, we present a case study of TerraSAR-X SAR images for Subsidence Hazard Boundary (SHB) extraction. The resulting data analysis gives an initial evaluation of InSAR applications within a mountainous region where fast movements and big phase gradients are common. Moreover, the experiment of four-dimension (4-D) Tomography SAR (TomoSAR) for structure monitoring inside the mining area indicates a potential near all-wave monitoring, which is an extension of conventional InSAR.

The upgraded PTB 600 m baseline: a high-accuracy reference for the calibration and the development of long distance measurement devices

The calibration and verification of high-precision electronic distance meters (EDMs) requires well-characterized and calibrated geodetic baselines. As the length measurements are performed typically over several hundred metres in air, a thorough understanding of the environmental conditions is necessary. In the course of a major refurbishment, the 600 m baseline of the Physikalisch-Technische Bundesanstalt at Braunschweig, Germany, was equipped with a dense environmental sensor network. This paper presents the characterization of this novel reference baseline, including the calibration of the inter-pillar distances, and identifies the major sources of uncertainty for such a length standard. A preliminary expanded standard uncertainty (k = 2) of is deduced for single-slope distance comparisons on the baseline. In the course of a full calibration, the additive constant cEDM of an EDM can currently be determined with an expanded uncertainty of U(cEDM)k = 2 = 6.1 × 10−5 m, and its scale correction sEDM with an expanded uncertainty of U(sEDM)k = 2 = 8.2 × 10−7. As an example, a femtosecond laser-based distance measurement over 600 m on this baseline is presented.

Structure from motion (SfM) processing of UAV images and combination with terrestrial laser scanning, applied for a 3D-documentation in a hazardous situation

ABSTRACT The integration of Terrestrial Laser Scanning (TLS) and Structure from Motion and MultiView Stereo techniques allows to obtain comprehensive models of complex objects by using each technique in contexts presenting the optimal operating conditions, as widely reported in bibliographic references. A different situation occurs for emergency surveys. In this case, time and security act as constraining factors, requiring the use of these techniques also in the most unfavourable conditions. In the case of photogrammetry, these include areas where the object surfaces are not perpendicular to the camera axis, and in the case of TLS, they include areas where laser beams are almost tangent to the surveyed object surfaces. These situations are anyway necessary for safely carrying out these surveys in the minimum possible time and cost. Although this kind of survey results locally in lower precision levels than those obtainable by these techniques in ideal conditions, it entails the possibility of obtaining complete models, e.g. including vertical external walls in inaccessible buildings, with controlled precision.

The SCAR GPS Campaigns: Accurate Geodetic Reference in Antarctica

During the XXIII Meeting of the Scientific Committee on Antarctic Research (SCAR) held in Rome in 1994 the Working Group on Geodesy and Geographic Information (SCAR WG-GGI) established a working program for the next two years. It was decided that SCAR Epoch GPS Campaigns should be organized as a continuation of former Epoch Campaigns.

The Project Corbas — Determination of Recent Crustal Movements in Costa Rica

The centralamerican country Costa Rica is located in a tectonically active area with interactions between the Cocos an Caribbean plate and the so-called Panama Block (see Fig. 1). The project CorBas (Niemeier et al, 1990) was inaugurated to develop a geodetic network for Costa Rica by use at the Global Positioning System (GPS). Repeated measurements of this network should provide direct information on actual plate motions and intraplate deformations.

Long Term Subsidence Analysis and Soil Fracturing Zonation Based on InSAR Time Series Modelling in Northern Zona Metropolitana del Valle de Mexico

In this study deformation processes in northern Zona Metropolitana del Valle de Mexico (ZMVM) are evaluated by means of advanced multi-temporal interferometry. ERS and ENVISAT time series, covering approximately an 11-year period (between 1999 and 2010), were produced showing mainly linear subsidence behaviour for almost the entire area under study, but increasing rates that reach up to 285 mm/yr. Important non-linear deformation was identified in certain areas, presumably suggesting interaction between subsidence and other processes. Thus, a methodology for identification of probable fracturing zones based on discrimination and modelling of the non-linear (quadratic function) component is presented. This component was mapped and temporal subsidence evolution profiles were constructed across areas where notable acceleration (maximum of 8 mm/yr2) or deceleration (maximum of −9 mm/yr2) is found. This methodology enables location of potential soil fractures that could impact relevant infrastructure such as the Tunel Emisor Oriente (TEO) (along the structure rates exceed 200 mm/yr). Additionally, subsidence behaviour during wet and dry seasons is tackled in partially urbanized areas. This paper provides useful information for geological risk assessment in the area.

Uncertainty assessment in geodetic network adjustment by combining GUM and Monte-Carlo-simulations

Abstract In this article first ideas are presented to extend the classical concept of geodetic network adjustment by introducing a new method for uncertainty assessment as two-step analysis. In the first step the raw data and possible influencing factors are analyzed using uncertainty modeling according to GUM (Guidelines to the Expression of Uncertainty in Measurements). This approach is well established in metrology, but rarely adapted within Geodesy. The second step consists of Monte-Carlo-Simulations (MC-simulations) for the complete processing chain from raw input data and pre-processing to adjustment computations and quality assessment. To perform these simulations, possible realizations of raw data and the influencing factors are generated, using probability distributions for all variables and the established concept of pseudo-random number generators. Final result is a point cloud which represents the uncertainty of the estimated coordinates; a confidence region can be assigned to these point clouds, as well. This concept may replace the common concept of variance propagation and the quality assessment of adjustment parameters by using their covariance matrix. It allows a new way for uncertainty assessment in accordance with the GUM concept for uncertainty modelling and propagation. As practical example the local tie network in “Metsähovi Fundamental Station”, Finland is used, where classical geodetic observations are combined with GNSS data.

Concept for a New Monitoring System for the Arch Dam Esch/Sauer

In this paper some ideas are presented and discussed in order to develop a completely new geodetic monitoring system for an existing arch dam. Taking into account the available knowledge on displacements of the structure and critical areas, it was possible to define requirements for the new monitoring system.

Monitoring von Hangrutschungen

In diesem Beitrag wird dargestellt, dass ein umfassendes geometrisches Monitoring von Hangen, Boschungen und Felsgraten mit den heutigen Sensoren und Verfahren der Ingenieurgeodasie realisiert werden kann. Sowohl fur das grosraumige Erkennen von bewegungsaktiven Zonen und das langfristige Monitoring risikobehafteter Bereiche als auch fur das kontinuierliche Verfolgen von abbruchgefahrdeten Sektoren sind leistungsfahige Konzepte und Methoden vorhanden.