Geology and Geomorphology

In 2003 the Italian Space Agency, supported by the Italian government, commissioned and funded the COSMO-SkyMed (COnstellation of small Satellites for the Mediterranean basin Observation) mission, an Earth Observation Dual Use System (civil and military) which represents the biggest Italian investment in the Earth Observation field. Thanks to their characteristics, the four satellites of the COSMO-SkyMed constellation can observe any part of our planet, under any weather and lighting (day/night) condition, due to the multimode high resolution and polarimetric X-band Synthetic Aperture Radar  (SAR) hosted on board, providing high resolution space images in very short times.  In the nominal configuration (four satellites equi-phased at 90° in the same orbital plane), the constellation is able to guarantee a revisit time of 12 hours (worst case) for the 100% of the Earth sites. The system,  fully operational since May 2011, is managed by a full-featured Ground Segment to exploit observation capabilities and provide SAR imaging servicing worldwide. The primary objective of COSMO-SkyMed system is the provision of services able to quickly answer the user needs in several application domains. Although the system is particularly devoted to support Emergency Management operations and Environmental Monitoring worldwide, it can be employed for the monitoring of archeological sites, as well, in order to rapidly detect damage caused by natural phenomena or human-produced. In this context COSMO-SkyMed system could be able to monitor the geometric variations of artifacts by means of change detection techniques, contribute to the measuring of disrepair and damage of archeological heritage and control the sites stability also in relation to possible bradyseism phenomena.

This paper aims to give an overview of the contribution provided by the COSMO-SkyMed mission in the framework of specific projects in which SAR data are exploited for the monitoring and the management of cultural and archeological heritage, showing some obtained results.

The mapping of natural resources in rapidly developing, commodity producing countries such as South Africa and Namibia is of vital concern for the local economy. Large arid areas with sparse vegetation in both countries make them a unique natural laboratory for the development and testing of new spaceborne-based applications for mineral exploration. However, so far either multispectral spaceborne or hyperspectral airborne data is being used for this task. Here a combined synergetic use of regional spaceborne multispectral data with local hyperspectral spaceborne data could help to cut the costs for expensive airborne hyperspectral campaigns. This can be achieved by using the increased capability of new multispectral, area-wide mapping missions such as Landsat-8 OLI and Sentinel-2 for characterizing the large iron absorption bands through new band indices in the visible and near infrared for the identification of iron oxide bearing areas. The surface mineralogy of these iron oxide bearing areas may then be characterized further on a local scale by hyperspectral spaceborne sensors such as Hyperion or EnMAP using automated mineral identification algorithms such as the EnMAP Geological Mapper (EnGeoMAP). This process facilitates the identification of areas of potential metal-sulphide oxidation and gossan formation, which are target zones for follow-up field visits in active exploration campaigns. Results from Iron Feature Depth (IFD) analysis from Sentinel-2 and Landsat-8 OLI data are shown and discussed together with EnGeoMAP results from Hyperion and simulated EnMAP data for mineral deposit sites in the lower Orange River region of South Africa and Namibia.

Subsurface geological and hydrological conditions are very important to the exploitation of subsurface resources, especially in remote and hyperarid areas where their location is not well mapped. Remote sensors, such as spaceborne and airborne optical, infrared and microwave sensors, are very efficient tools to study subsurface features in such hyperarid areas. Among these remote sensors, radar is the best for subsurface investigations because with lower frequency microwave, it has some penetration ability. Since the first unveiling of the subsurface valleys buried under a thin dry sand layer in the eastern Sahara by SIR-A’s microwave images at low frequency (e.g. 1.25GHz/24 cm, L-band) [1], the adoption of radar remote sensing to geologic analysis and groundwater exploitation in hyperarid areas has attracted a lot of interest from many hydrologists, geologists and remote sensing communities. Radar remote sensing is more and more utilised to study subsurface features (such as paleo-rivers and crater-like features [2-6]) and related geologic process, such as dune formation, flow direction and sand accumulation [7-8].

In summary, three properties of radar images have been utilised in the field of subsurface mapping, namely (1) radar backscatter (tone in SAR images), (2) InSAR derived topographic data, and (3) polarimetric SAR data. The radar backscatter signal shows the appearance of subsurface features, which is a direct indicator. The InSAR derived topographic data is especially relevant with the advent of global Digital Elevation Models (DEMs) produced at different electromagnetic wavelength ranges from spaceborne earth observations, such as microwave frequencies from SRTM (X- and C-band), TanDEM-X (X-band) and ALOS/PALSAR (L-band) as well as stereo-optical, such as ASTER or PRISM or lidars such as ICESat (the Ice, Cloud, and land Elevation Satellite). InSAR derived DEMs at L-band wavelength are assumed to penetrate deepest into sand layers, thus, ALOS/PALSAR InSAR can potentially be applied to obtaining subsurface DEMs.

Focusing on the spaceborne radar instruments to date, this paper analyses the possibility of mapping subsurface features by radar backscatter and subsurface elevation measurement by radar interferometry. Radar images over desert regions in the eastern Sahara and in the Gobi desert are studied and both their advantages and disadvantages of its application into mapping subsurface features, such as aquifers and bedrocks, are analysed. Optical and radar images are compared to show the different appearances of surface and subsurface features. Different DEMs, including ASTER DEM, SRTM DEM and an InSAR derived DEM, are compared with each other to demonstrate the penetration depth of radar signals at C-band and L-band. The results show that radar images can be acquired to date are useful for shallow subsurface researches, in favourable study areas, but they can hardly to be applied into mapping aquifers and deep buried bedrocks. To address these much deeper features, much lower frequency radars [9] need to be employed and an example of these will be shown.

This work is partially supported by the CSC and UCL through a PhD studentship at UCL-MSSL.

McCauley, J.F.; Schaber, G.G.; Breed, C.S.; Grolier, M.J.; Haynes, C.V.; Issawi, B.; Elachi, C.; Blom, R. Subsurface valleys and geoarcheology of the eastern Sahara revealed by shuttle radar. Science 1982, 218, 1004-1020.

Schaber, G.G.; McCauley, J.F.; Breed, C.S. The use of multifrequency and polarimetric SIR-C/X-SAR data in geologic studies of BirSafsaf, Egpyt. Remote Sens. Environ. 1997, 59, 337-363.

McCauley, J.F.; Breed, C.S.; Schaber, G.G.; Mchugh, W.P.; Issawi, B.; Haynes, C. V.; Grolier, M. J.; Kilani, A. E. Paleodrianges of the eastern Sahara - the radar rivers revisited (SIR-A/B implications for a mid-Tertiary trans-African drainage system). IEEE Trans. Geosci. Remote Sens. 1986, GE-24, 624-648.

Schaber, G.G.; McCauley, J.F.; Breed, C.S.; Olhoeft, G.R. Shuttle imaging radar: physical controls on signal penetration and subsurface scattering in the eastern Sahara. IEEE Trans. Geosci. Remote Sens. 1986, GE-24, 603-623.

Berlin, G.L.; Tarabzouni, M.A.; Al-Naser, A.H.; Sheikho, K.M.; Larson, R.W. SIR-B subsurface imaging of a sand-buried landscape: Al Labbah plateau, Saudi Arabia. IEEE Trans. Geosci.   remote Sens. 1986, GE-24, 595-602.

Dabbagh, A.E.; Al-Hinai, K.G.; Asif Khan, M. Detection of sand-covered geologic features in the Arabian Peninsula using SIR-C/X-SAR data. Remote Sens. Environ. 1997, 59, 375-382.

El-Baz, F.; Maingue, M.; Robinson, C. Fluvio-aeolian dynamics in the north-eastern Sahara: the relationship between fluvial/aeolian systems and ground-water concentration. J. Arid Environ. 2000, 44, 173-183.

Robinson, C.; El-Baz, F.; Ozdogan, M.; Ledwith, M.; Blanco, D.; Oakley, S.; Inzana, J. Use of radar data to delineate palaeodrainage flow directions in the Selima Sand Sheet, eastern Sahara.Photogramm. Eng. Remote Sens. 2000, 66, 745-753.

Heggy, E., Rosen, P.A., Beatty, R., Freeman, T., and Y. Gim, “Orbiting Arid Subsurface and Ice Sheet Sounder (OASIS): Exploring desert aquifers and polar ice sheets and their role in current and paleo-climate evolution,” presented at the IGARSS 2013 - 2013 IEEE International Geoscience and Remote Sensing Symposium, 2013, pp. 3483–3486.

A review of earth observation (EO) technology for onshore oil and gas activities revealed a range of challenges the industry faces, now and in the next five years, which can be addressed through integrated application of satellite EO. Current gaps in EO technology were identified, many of which could be addressed through joint program of research and development, guideline development, and training.

Conducted under the Value Added Element of the European Space Agency (ESA) Earth Observation Envelope Programme, the EO for Oil and Gas Project (EO4OG) – onshore – involved collaboration between nine companies and organizations that are active in providing services to the oil and gas industry. Consultation with industry formed a key element of the project, as well as the leading industry organization the International Oil and Gas Producers Association (IOGP).

The applied research design followed three phases: 1) industry consultation period to define industry challenges and requirements; 2) review of EO capabilities and gap analysis compared to requirements; and 3) development of a roadmap for future cooperation to advance the appropriate application of EO technology.

The industry consultation documented more than 100 geo-information challenges across seismic planning, surface geology mapping, subsidence monitoring, environmental monitoring, and logistic operations and survey planning. Ultimately, the challenges required a consolidated set of geo-information to be addressed, often through analysis and integration of different types of EO-derived information and modelling. To support the oil and gas industry to understand the products that are available and the EO industry to appropriately described available products and services, a suite of 57 products were specified using a standard product template. Of these, 16 were considered “integrated” products, which are built from a combination of EO products and modelling. The utility of each product was evaluated for each of five recognized oil and gas project lifecycle stages. Many products could be used across technical themes, creating opportunity for cost efficiency and improved decision making across the oil and gas lifecycle.

A number of case studies were if successful application of EO in the oil and gas sector, covering existing onshore projects in North and South America, Europe, Middle East, Southeast Asia, and Africa. Equally important was a systematic gap analysis of EO products, which were evaluated on: 1) capabilities; 2) demand for quality and industry drivers; and 3) current industry utilisation levels. The gap analysis revealed interesting results, identifying several gaps in utilisation – where an existing product could meet quality requirements, but utilization was low. In contrast, areas of high demand were identified that cannot be met with current EO product capabilities.

Major EO product strengths include: geographic coverage and rapid delivery; mix of available sensors and resolutions; imagery archives and open access data; and remote access to address health, and safety or security concerns. Reflective of product strengths, major opportunities for further EO product mainstreaming include: promotion as a low-cost, rapid information delivery option; improvements to vertical and horizontal accuracy for remote area projects; improvements to site monitoring and security.

A roadmap was established that identified the need to support research and development, including Joint Industry Projects (JIP), improvements to EO data archive access, including open data. Major activities were identified related to: communications across the industry; standards, guidelines and training; and integration with complimentary technologies such as Unmanned Aerial Vehicles (UAVs).

The EO4OG project outputs are freely available through the OGEO Portal (http://www.ogeo-portal.eu/), a collaborative forum for the sharing of information between the EO services industry and oil and gas operators. In the future, the results will be reviewed with the EO service sector with the aim being to update and maintain the information.

Mediterranean areas form part of a fragile ecosystem and are greatly influenced by extensive activities that imply agricultural land use affecting soil surfaces and their conditions. Monitoring soil surface changes is important, because it represents a major factor of transformation in soil landscapes.

The objective of this study is to identify and characterize the different land surface features with the main focus on bare soils that are managed for traditional rainfed cultivations using a combination of fully polarimetric RADARSAT-2 and hyperspectral data as well as a high resolution DEM.

The study area is located within central Spain in the Province of Toledo that belongs to the Autonomous Community of Castilla La Mancha. This area has a Mediterranean climate, with a continental variant that shows cool winter temperatures, and low precipitations with maximum in late autumn, winter and late spring and an outstanding minimum in summer. In the test site, a mosaic of different soil surface horizons is present: A (top soil surface), B (subsoil) and C (parent rock). There exists an extensive characterization of soil parameters and field spectroscopy measurements that have been compiled in a georeferenced database. Based on this information and using hyperspectral imagery, a map indicating the different soil surface characteristics has been generated and is used to validate the information obtained with the newly acquired RADARSAT-2 data. for

A processing chain has been developed that includes 1) multilooking of the data, 2) estimation of the polarimetric coherency matrix based on the use of bilateral filter which separates homogeneous from heterogeneous areas while preserving edges, 3) the extraction of different polarimetric parameters that are used as 4) input for a supervised classification algorithm (SVM - Support Vector Machine) and the associated the training data for the classification were generated from the existing georeferenced database as well as newly acquired field observations.

Preliminary results show that the information acquired from the RADARSAT2 data is able to distinguish different soil surface covers. These differences are mainly due to changes in the surface texture of the soil cover and where ploughing practices are implemented. The latter practices are well established between clay soils that form sizeable aggregates and sandy soils which have smooth surfaces. Furthermore, soil conditions such as humidity are also related to the different soil types and can be an important factor for distinguishing the most recent management of soil areas compared to fields that are left in fallow.