EP7 - Earth Observation


Aims

DThe sub-project Earth Observation investigates the ground displacements in Thuringian Basin for the purpose of retrieving general information on surface dynamics, i.e. gaining knowledge on the active processes taking place in the basin. In order to derive the spatio-temporal evolution of the surface dynamics, differential interferometric synthetic aperture radar (dInSAR) is utilized which allows the detection of displacements rates in the mm per year range. Special emphasis is put on surface movements created by ground water level changes as well as subrosion or mining-induced subsidence. For this purpose, multi-sensor radar data covering different seasons, weather conditions and ground water levels are interferometrically analyzed.

Working area

Erfurt: Analysis of periodic ground water level changes

Bad Salzungen: ground water + subrosion subsidence

Schmalkalden: ground water + subrosion subsidence

Sondershausen: mining induced subsidence

Methods

An advanced dInSAR technique of Persistent Scatter Interferometry (PSI) is the method of choice for long term monitoring of the study sites. First the radar scenes covering one research area will be put in a stack coregistered with a very high accuracy. Pixels with a stable signal of both phase and amplitude over time will be selected as persistent scatterers (PS). Multi-step iteration of the stack will reduce atmospheric disturbances while reconstructing the phase signal of the PS, thus allowing deducing the motion of the single pixels relative to a reference point. The resulting data can be compared / completed with data from ground water level gauges or land surveying networks.

Method

Results

Urban areas and sealed surfaces can be monitored with PS analysis particularly good. Long, continuous time series with a short revisit time are crucial for obtaining high accuracy results. Over Erfurt the same trends can be observed in the results of radar interferometry as well as in the ground water level measurements, further investigation is promising. In the Sondershausen area, mining induced subsidence areas have been identified and their subsidence rates derived with mm accuracy (see Figure 1 for the rates measured in the period of 2004-2010 by the satellite Envisat-ASAR). A successful analysis of multi-sensor data over a timespan more than 15 years (see Figure 2) demonstrates the potentials of PSI for long term monitoring of the displacement.

2_ASAR_PS_Vertical_DeformationRate_Map_scissored-klein

Figure 1: Results of ASAR data over Sondershausen. In the center of the village sink rates of up to 12 mm / year can be observed.


temporal_coverage_sensors_Sondershausen

Figure 2: Overview of the coverage of different sensors over Sondershausen area.

Team

Members of the Team EP7 you will find here