Our Spatial Planet

Remote sensing has been extensively used geology, mining exploration, oil, gas and pipeline planning. Recent introduction of new sensors and techniques to improve accuracy and efficiency are allowing planners to perfom virtual field trips to gather accurate information before arriving on site. From the first assessment of a project to the logistical operation, and on going monitoring, remote-sensing is an indispensable tool for all stages of any major mining project. Time and cost as well as risks can be greatly reduced through the use of Remote sensing technologies.

A range of sensors and resolutions are available for the mining industry and an accurate assessment of the most suitable data for a specific task should to be conducted to get the greatest benefit. The following list gives an overview of which data and sensors are currently used:

· Optical imagery for vegetation classification, environmental impact assessments, site rehabilitation, and operation monitoring:

o  ALOS PRISM and Spot which offer relatively large coverage with a resolution around 2.5m and very soon the Rapideye constellation with its daily coverage and 5m multispectral resolution.

o    High resolution satellites such as IKONOS, QuickBird, EROS-A/B which offer a narrow swath but 1-m and sub-metre resolution

o     Digital airborne imagery up to 5cm resolution

o    Airborne Hyper-spectral sensors with some systems collecting up to 220 bands.

Fast monitoring over a mining site

· All weather Radar data for mine subsidence, stock pile, pipeline monitoring and gold exploration:

o  TerraSAR-X, Radarsat-2, Cosmo-Skymed, for a resolution range from 100m up to 1m

o    Airborne IFSAR with sub-meter resolution (ORI from Intermap)

· Digital elevation model for planning, modelling and quantitative structural mapping:

o Spaceborne Radar interferometry data for centimetre-scale changes measurements.

o   Stereo imagery from Airborne sensors

o Stereo imagery from Spaceborne sensors such as ALOS PRISM, Spot, IKONOS, QuickBird, EROS-A/B

o   IFSAR DEM form airborne IFSAR systems such as Intermap, Fugro.

o   LiDAR

Advanced processing methodology also allows for the manipulation of basic data sets revealing features that may be of interest in geological interpretation such as the surface benath sand dunes.

ALOS PRISM DEM

Digital Elevation Model after dune removal process

All these data are usually integrated into modeling software, GIS systems and 3D-visualisation tools in addition to ground information and thus present invaluable decision level information.

Current state-of-art in commercial and research based SAR Systems.

Air-Borne Systems

Commercial – Very few purely commercial players exist in this field

1.     Intermap IFSAR – Operational X-Band single pass Interferometric System with proven track record and very large archive of proven quality data (All of USA, Europe, Britain has been mapped as well as part of Asia and Australia). Long wavelength system for foliage penetration is currently available as repeat-pass system with multi-frequency single-pass interferometric system in development.

2.     Fugro-EarthData GeoSAR – Newly operational for X-Band and P-band single pass interferometry. Available data archive is limited and data validation is not wide-spread. Theoretically should produce good quality DEM’s using P-Band but this may conflict with the X-Band results, needing reconciliation. The system is ex-NASA. The accuracy in the system is achieved by redundancy/repeat flights. A good set of samples can be obtained at the NOAA site.

3.     Orbisat InSAR – A Brazilian system with InSAR capability in X-Band and  P-band. No validation available

Research – A number of research systems exist, operated by space agencies and educational institutions. The data from these systems has limited availability and is based on research campaigns. A suitable summary is on the POLSARPRO site.

1.     AIRSAR(NASA/JPL) – The elder statesman of air-borne systems, last known campaign was in 2004.

2.     EMISAR(DCRS) – Technical University of Denmark dual-band(L/C) fully polarimetric system.

3.     ESAR(DLR) – Quad-Band(X/C/L/P) fully polarimetric system with very high quality data used for Insar, Polsar and Polinsar research. This system served as a template for the TerraSAR-X sensor.

4.     Pi-SAR(NASDA-CRL) – JAXA Airborne L-Band system, the inspiration behind JERS and ALOS-PALSAR.

5.     RAMESES/SETHI(ONERA) – Someone in France must be obsessed with Egyptian history and pharaohs, or may be it is related to the sand penetration experiments with these systems.

6.     SAR-Convair(CCRS) – Polarimetic X/C-Band system used as a test-bed for Radardat 1 and 2 sensors by the Canadians. Mainly used for ship detection research, and ocean monitoring.

Space-Borne Systems – Recent years have seen the launch of numerous SAR sensors, both civilian and military.

The following SAR satellites are those that have readily accessible data, are currently operational or will be in the near future (which can mean anytime in the next 5 years given the nature of the space industry – you can really feel the relativistic time dilation, we must be near a black hole).  Among the military ones, we can mention SARLupe-1 and 2(Germany) , YaoGan(Chinese), and many more.

Currently In-Orbit Systems – These are either old die-hard systems, long past their scheduled expiry date or recently launched top-of-the-line sensors.

1.     RADARSAT-1 – The long lived Canadian SAR system operating in C-Band HH.

2.     ENVISAT-ASAR – SAR sensor on the multi-sensor Envisat bus. The data from this sensor is accessible for research from a rolling archive over the last 15days. The sensor can operate in alternate polarization mode.

3.     ALOS-PALSAR – The first fully polarimetric L-Band space borne sensor. The data from this sensor is heavily consumed by the Kyoto and Carbon project for global forest monitoring. It collects on a fixed schedule over all land-mass. The data is highly affordable and of good quality.

4.     TerraSAR-X – Newly launched poster child of the SAR world, first commercial SAR sensor to provide up to 1m resolution. Alternate polarization mode is operational, full-polarimetry and along track interferometry are some of the research modes available.

5.     RADARSAT-2 – After long delay, it is the first fully polarimetric C-band spaceborne system and provides data to 3m resolution.

6.     Cosmo-Skymed  - 3 out of 4 satellites are currently in orbit. With a very short revisit time, this new X-band polarimetric SAR constellation is a real advantage for monitoring applications.

Planned/To-be-launched-soon systems – These are the bad boys, getting to school late or the toddlers which show great promise. Not yet in orbit but will be nice to have data from them.

1.  Sentinel-1 – Follow on to the aging ENVISAT system mentioned above, with upgrades with new technology in C-band. Unlike its predecessor, it will be a smaller and dedicated SAR bus, other optical sensors will have to find their own rides on Sentinel 2 and 3. It is due for launch in 2011

2.     TerraSAR-L(Cartwheel) and Tandem-X – The novel concept in SAR systems is a constellation, this will allow single pass along-track and cross-track interferometry.

3.     MAPSAR – An L-band joint program between INPE(Brazil) and DLR, due some time the next decade.

4.     RADARSAT Constellation – Another program due next decade or after that is designed to provide daily global coverage using SAR.

There are probably more exotic sensors, both for research and military purposes and any comments on those sensors are more than welcome.