Surface subsidence

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PRODUCT DESCRIPTION

Category

• Topographic information
• Impact assessment
• Change detection / continuous monitoring
• Land cover / use
• Near surface geology

• Surface deformation
• Precision ortho-images
• Terrain information
• Water quantity & quality

Uses

Challenges addressed

• Development and Operations – Ground Stability/Geotechnical
• Closure and Aftercare – Affected Stakeholders

Geo-information needs

• DO-19: Underground operations – surface subsidence
• CA-5: Demonstration of no impact on national heritage locations

Description

This product provides information on the surface subsidence during underground operations, based on the satellite-based InSAR (Interferometric Synthetic Aperture Radar) technique. It provides mm-precise measurements over large areas on a weekly-monthly basis and can serve as scanning tool for the complete area above the mine and the direct environment. Depending on the satellite, up to 100,000 measurements per km² can be obtained.

Typical mining applications of this product are monitoring the subsidence of the ground on top of an underground mine, the effects of certain backfilling or ground support approaches and the effects of the mining operation on the environment and the surrounding infrastructure. The advantages are that large areas can be monitored on a regular basis, in a fully automated manner and without human intervention, providing a spatially dense view of the effects of underground operations. Furthermore, by using satellites, a uniform data format and quality can be obtained over all mines in the portfolio.

InSAR is based on radar images, as acquired by various radar satellites. The products from these satellites differ in terms of number of measurements per km², measurement frequency, price (free vs. paid imagery) and availability. In most locations worldwide there is imagery available dating back to 2015 and for some locations even back to 1992. Therefore, it is easy to obtain a baseline of the deformations around the mining area and thereby context of what is or has been happening. By using multiple satellites, vertical as well as horizontal (in the east-west direction) movements can be tracked.

Known restrictions / limitations

The highest measurement frequency that current satellites can obtain is once per couple of days, which could be too low for certain applications. If the deformations leading up to a failure can occur in the timespan of minutes/hours rather than days, other systems for intervention are required, such as GPS or ground-based radars.

Lifecycle stage and demand

Exploration

Environmental Assessment and Permitting

Design, Construction and Operations

Mine Closure and Aftercare

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Exploration:

• Investigating fault movement for exploration purposes

Environmental Assessment & Permitting:

• Establishing a baseline measurement of movements already occurring in the area before the mine was built and taken into operation; assessment of regulator rules.

Design, Construction & Operations:

• Design: Establishing a baseline measurement of movements already occurring in the area where the mine will be built. Potential to adjust the design the strategy based on that information.
• Construction & Operations: Monitoring the surface subsidence and the effect of underground operations.

Mine Closure & Aftercare:

• Monitoring the surface subsidence after mine closure

Geographic coverage

EARSC Thematic Domain

Domain

PRODUCT SPECIFICATIONS

Input data sources

Website

Minimum Mapping Unit (MMU)

The satellite can detect very small features (~decimeters), provided that objects and/or surfaces of interest reflect well enough. Generally, solid, stable, angular objects are the best reflectors.

Accuracy / constraints

Thematic accuracy:

The technique works best on solid, stable, angular objects like infrastructure, buildings, solid rock, etc. Water cannot be measured, and vegetated surfaces are more difficult to measure.

Spatial accuracy:

Dependent on the satellite resolution. The measurement can be located on sub-pixel level, typically in the order of 1-5 meters.

Measurement accuracy:

The deformation/movement of the infrastructure can be determined with a precision of around 1 mm/yr.

Accuracy assessment approach & quality control measures

The quality is assessed by automated, thoroughly tested, quality control algorithms, delivering validated results. The quality of the product and the approach taken are described in an automatically generated report, ensuring high quality and reproducibility.

Frequency / timeliness

Observation frequency:

Depending on the satellite, varying from once per 4 to 24 days.

Timeliness of delivery:

Depending on the satellite provider, the service provider and the type of application (within 1-5 working days).

Availability

• Global coverage with free imagery, lower resolution, including archive since 2015 and in some locations since 1992.
• Global coverage on demand with paid imagery, higher resolution. Archive imagery available in some locations.

Delivery / output format

• Data via API (Application Programming Interface), as GIS file format (geopackage, shapefile, .kml, .csv, etc.) or in a webviewer.
• Triggers via API or email.
• Automated reporting in pdf.

USE CASE