ASI-SRV GATEWAY: AN INTEGRATED TOOL TO SUPPORT THE MONITORING ACTIVITIES

M. Silvestri a, *, M. Musacchio a, M.F. Buongiorno a, S. Zoffoli b, ASI-SRV Team a

a Istituto Nazionale di Geofisica e Vulcanologia,Via di Vigna Murata 605, 00143 Rome, Italy - (malvina.silvestri,

massimo.musacchio, fabrizia.buongiorno)@ingv.it b Agenzia Spaziale Italiana, Viale Liegi 26, 00198,Rome, Italy – simona.zoffoli@asi.it

KEY WORDS: Remote sensing, volcanoes monitoring, webgis, integrated system ABSTRACT: The ASI-SRV (Sistema Rischio Vulcanico) project is devoted to the development of an integrated system based on EO and Non EO data to respond to specific needs of the Italian Civil Protection Department (DPC). ASI-SRV provides the capability to import many different EO and Non EO data into the system, it maintains a repository in which the acquired data are stored and generates selected products which will be functional to the different volcanic activity phases. The processing modules for Radar and EO Optical sensors data allow to estimate a number of parameters which include: surface thermal proprieties, gas, aerosol and ash emissions and to characterize the volcanic products in terms of composition and geometry, surface deformations in terms of displacements and velocity. All the generated products are related to Italian actives volcanoes and three test sites have been chosen to demonstrate the capability of this integrated system: Vesuvio, Campi Flegrei (Campania region) and Etna (Sicilia region), all in Italy. The produced results have been disseminated through a WEB-GIS interface which allows the Italian Department of Civil Protection to overview and assimilate the products in a compatible format respect to their local monitoring system in order to have an immediate use of the provided information. In this paper some results obtained by means of modules developed within the ASI-SRV project and dedicated to the processing of EO data of the last Etna eruption of 15th May 2008 and the short event in the night between 12th and 13th January 2011 are presented.

* Corresponding author.

1. INTRODUCTION

The ASI-Sistema Rischio Vulcanico (SRV) project is started in January 2007 and is devoted to the development of a pre-operative integrated system based on Earth Observed (EO) and Non EO data to respond to specific needs of the Italian Civil Protection Department (DPC) and to improve the monitoring of Italian active volcanoes. The ASI-SRV provides support to the following volcanic activity phases addressed by the DPC: 1) Surveillance and early warning, 2) Sin-eruption phase, 3) Post-eruption phase

ASI-SRV project provides the capability to manage the import many different EO and Non EO data into the system, it maintains a repository in which the acquired data are stored and generates selected products which could be functional to the phases described above. All technical choices and development of ASI-SRV are based on flexible and scalable modules which have take into account also the new coming space sensor and new processing algorithms considering the national and international scenario in the space technologies. An important step of the project development regards the technical and scientific feasibility of the provided products. In fact the technical feasibility depends on the data availability, accuracy algorithms and models used in the processing and of course the possibility to validate the results by means of comparison with other independent measurements (EO and non-EO). The EO data (ASTER, HYPERION) are furnished by external providers as NASA, ESA by means of CAT 1 protocol or acquired systematically. Moreover NOAA-AVHRR and MODIS data are acquired by the system owned and directly managed by Istituto Nazionale di Geofisica e Vulcanologia (INGV). The EO data

used in the ASI-SRV project have different format, are not calibrated and typically acquired in “sensor geometry”. All data are ingested into SRV system and are available to the processing functionality installed into main ASI-SRV infrastructure.

Together Optical data, ASI-SRV has generated also products coming from the analysis of Radar data (ERS, ENVISAT, COSMO-SkyMed, ALOS, RADARSAT). Example of main results will be reported in this paper.

2. ASI-SRV ARCHITECTURE

2.1 The production chain

The ASI-SRV architecture is based on a distributed client/server architecture which implies that different processors need to ingest data set characterized by a constant and common structure.

The ASI-SRV production chain generates three levels of products and the modules are dedicated to the generation of all the L1 and to the L2D products. (Figure 1). The processors implemented in the ASI-SRV system are able to run in parallel more than one parallel instance and the processing modules for EO Optical sensors data, are based on procedures mainly developed by INGV and “University of Modena and Reggio Emilia”. These procedures allow to estimate a number of parameters which include: surface thermal proprieties, gas, aerosol and ash emissions and to characterize the volcanic products in terms of composition and geometry.

Figure 1. ASI-SRV production chain. The EO Radar sensor data have been used in order to obtain ground deformation measurement via Differential Interferometric SAR (DInSAR) techniques by using ERS/ ENVISAT SAR data and COSMO-SkyMed data via the application of the Small BAseline Subset (SBAS) technique developed by IREA. In order to standardize the EO data in HDF format including all attributes needed by each different processor and then the publication of the results, pre-processing modules have been considered to the production of all Level 1 dataset (Figure 1). These modules allow to publish the EO added value derived data by means of dedicated webGis interface. The pre-processing package starts with the radiometric Calibration, the georeferencing, the cut-mosaiking and Atmospheric Correction Tool (CIRILLO) (Teggi et al., 2005, Bertacchini et al., 2007) and after the core process represented by scientific algorithm dedicated to the extraction of added value products and end with the publication of the vector layer via GIS Tool Analyst (GTA) via a dedicated WEB-GIS tool. The test sites considered (Etna and Vesuvio-Campi Flegrei, both in Italy) have well developed ground monitoring network that ensure a suitable validation for the retrieved products.

3. WEB GIS

3.1 Dissemination (DIS) tool

This tool allows the users to overview and assimilate the products in a compatible format respect to their local monitoring system in order to have an immediate use of the provided information. Through a web link, the users access to the dissemination (DIS) tool to visualize the different products organized in three different phases and different sites, interrogate the product in order to obtain main information and download the data in ESRI shape format in order to visualize on ARCGIS or other different product visualizations software. Because shapefiles do not have the processing overhead of a topological data structure, they have advantages over other data sources such as faster drawing speed and edit ability. They also typically require less disk space and are easier to read and write using a variety of free and non-free programs. The DIS tool provides a Web GIS application to let User access SRV data and parameters through: navigable maps, graphics and charts (as maps drill-down on data), a customizable

dashboard with an aggregate of the relevant parameters for “at-a-glance” visibility of early & warning situation. Taking advantage of the OGC Catalog service , that defines common interfaces to discover, browse, and query metadata about data, services, and other potential resources, this web GIS publish data using OGC protocols and practices, especially for what concerns maps visualization, layer management and drill-down data retrieval. The web GIS is able, on one side, to provide SRV results on demand (data-browsing scenario) and on the other hand to provide an alerting capability to catch DPC attention when some of the monitored parameters approach a (configurable) threshold value (monitoring scenario). 3.2 Data-browsing scenario

In the data-browsing scenario, the web GIS gives some basic GIS-like tools for the correct interpretation of data and results presented. For example: time filter on data, map layers management, drill-down on data. Moreover in the data-browsing scenario the opportunity to download data is offered to the user. 3.3 Monitoring scenario

In the monitoring scenario, the web interface presents a sort of panel or dashboard with gauges and indicators. The indicators represent the status of relevant parameters and information in a early & warning phase. The goal of the indicators is to represent graphically, in an effective way, the overall “status” of the site of interest in terms of its volcanic activity. Indicators graphically facilitate the “at-a-glance” monitoring of the site. The DIS tool allows a deep customization of the dashboard in terms of type of indicators to use parameters to represents and threshold values. The web interface in the monitoring scenario has been arranged according to the following hierarchy: - first hierarchical level: test sites - second hierarchical level: monitoring phases So, for each test site, the system shows a section for each of the following 3 main phases: Pre-eruptive phase, Sin-eruptive phase and Post-eruptive phase. When logging into the system the user first chooses the test site and successively chooses the monitoring phase. According to this selection, the user accesses to the related subset of products The user selection of the monitoring phase is independent on the actual status of the test site. In other words, regardless of the phase in which actually a certain test site is, the user still has the possibility to choose any phase. For example, even during a sin-eruptive phase, the user has the possibility of exploring the data produced during the pre-eruptive phase (e.g. for investigation purposes) and so on. In fact the generation of products, performed by the SRV operator using the SRV processing modules, depends on the eruptive phase, but the user data access via the WebGIS is independent on this. The transition between one phase and another (for example between pre-eruptive and sin-eruptive) is formally decided by the DPC. Nevertheless, for configuration control purposes there is no direct link allowing the DPC user to automatically switch the SRV system from one phase to another. So, in line with the current existing protocol, the phase transition will be communicated by the DPC to the SRV system operators via independent means (e.g. telephone, fax, etc.) and it will be responsibility of the operator to switch the system operations accordingly.

Together with shape format, product files have been also written according to a standard format GML or Geography Markup Language which is an XML based encoding standard for geographic information developed by the OpenGIS Consortium (OGC). Note that the concept of feature in GML is a very general one and includes not only conventional "vector" or discrete objects, but also coverages and sensor data GML encodes the GML geometries, or geometric characteristics, of geographic objects as elements within GML documents. The geometries of those objects may describe, for example, roads, rivers, and bridges. 3.4 DIS tool architecture: Server and client

The DIS tool general architecture is composed of following elements: DIS Server and DIS Client. The DIS Server is a part of the web application server mainly composed by a number of web services that offer core functionalities to the DIS Client. The main services offered by the DIS Server are:

• Mapping (based on the Web Map Service and Web Feature Service specifications by OGC)

• Data serving (based on the Web Feature Service and Web Coverage Service specification by OGC)

• Data pushing (for the monitoring scenario)

• Authentication and Accounting Data serving service differs from Data pushing service since the first is an “on demand” serving service while the latter is a service based on a producer-consumer model to ensure a near real time response. The DIS Client is a web application client stub mainly composed of a set of HTML and Flex components that uses the DIS Server services to present data and information to the web user. The DIS Client components include:

• A map navigation component with selection, zoom and pan functionalities

• A map layer management component

• A number of charting components

• A number of gauge and indicator components The map layer management component allows the user to select the map layer to visualize, according to the monitoring phase in which the selected test site is. For example, during the pre-eruptive phase of a certain test site, a number of products are generated (e.g.: deformation maps, surface temperature, etc.). Starting from an initial pre-defined configuration, the user may choose to switch on/off certain layers. The DIS client is the access point for the users for receiving the products generated by the SRV system operators. As such the client will not allow the user to directly perform any processing operation on the system, but only to query, visualize and analyse the product available on the system.

4. DISCUSSION AND MONITORING ACTIVITIES

SRV project offers an active contribute of the Italian DPC in order to meet the requirement requested especially regarding the delivery time of the products in the Crisis Phase during the volcanic eruptions. An almost persistent volcanic activity of Etna volcano has allowed the generation of products related to the sin-eruptive and post-eruptive phase, whilst Vesuvio and

Campi Flegrei volcanoes have been representative to quiescent phase products analysis, especially regarding the surface deformation map. In this work we have decided to showed two different example of how ASI-SRV system works: the eruption of Mt. Etna in May 2008 and the last short eruptive event of the same volcano in January 2011. In the next, example of different products generated in the three phase are reported. 4.1 ASI-SRV: surveillance phase and early warning

In order to monitor volcanoes in constant and continuous way, it is important to use systems retrieving physical-chemical parameter of the volcanoes analyzing each variation. For this reason all data coming from satellites having different resolution in terms of space and time can be considered together with the ground networks. For the analysis of the surface thermal characteristics, the available algorithms (Gillespie et al., 1998, Realmuto, 1990) allow to extract information useful to detect small changes in the retrieved parameters. The thermal analysis is directed to the early identification of temperature variation on volcanic structure which may indicate a change in the volcanic activity state. At the moment the only sensor that presents good technical characteristics for the prevention phase is the ASTER sensor (90 m pixel) on NASA satellite TERRA, even if this parameter has been retrieved also using AVHRR and MODIS data. The surface temperature has been analysed considering the pre-eruptive phase (1st of May 2008) and crisis phase 13th of May Unfortunately the bad weather condition have prevented a reliable estimation of surface temperature during the eruption. Figure 2 shows the maximum temperatures near lava flow considering the three sensors.

Figure 2. comparison of surface temperature measured by MODIS (blue cross), AVHRR(red circle), ASTER (yellow star) It is important to consider that results obtained using low resolution (MODIS and AVHRR) are comparable. The high value of temperature obtained with ASTER is due to the high resolution of this sensor with respect to the MODIS and AVHRR (90mt vs 1km) and for this reason it can considered the best sensor for this product. Another important product is the multi-parametric analysis that gives a probability index of an eruption. It is mainly based on a Bayesian procedure and it relies on the fuzzy approach to manage monitoring data. The method deals with short- and long-term forecasting, therefore it can be useful in many practical aspects, as land use planning, and during volcanic emergencies. Typically the probability index is very low for a quiescent phase (Figure 3) and it increases when the activity starts in terms of ground deformation or physical–chemical parameters.

Figure 3. Multiparametric analysis during the quiescent phase. During the last short eruptive event on 12th and 13th January 2011, this product has detected several days before the event an increase of the eruption probability (Figure 4).

Figure 4. few days before the erution event of 12th and 13th January 2011 of Etna site

Together with these products information on the estimation of concentration and flux of sulphur dioxide (SO2) (Pugnaghi et al., 2006), water vapour and volcanic aerosol optical thickness (Spinetti et al., 2007) are given. The deformation velocity map and the displacement time series (Figure 5) by SAR data using the SBAS technique (Berardino et al., 2002) complete the surveillance phase and early warning products.

Figure 5. Deformation velocity map and the displacement time series of

Etna site

4.2 ASI-SRV: Crisis phase

When an eruption starts, the crisis phase begins and the products generated are characterized by higher update frequency by means of low spatial resolution optical sensors (MODIS and AVHRR) which beside the products generated starting from higher spatial resolution sensors (ASTER and HYPERION). These products contribute to help the DPC activities to the decision of emergency plan giving information on the evolution of volcanic crisis. The products regarding this phase are divided in two classes: - The first class is mainly finalized to the estimation of the

effusion rate for active lava flows (Lombardo et al., 2004). (Figure 6 and Figure 8)

Figure 6. Active lava flow measured with AVHRR and thermal flux

statistics Middle sized data, like HYPERION, yield to an estimation of the fractional area of the hottest part of thermal anomalies (e.g molten core), and the temperature of the cooler component (e.g crust) (Figure 7). Unfortunately the low temporal resolution of these data, every 16 days, does not allow a monitoring of volcanoes activities, but obviously can be used to validate the extension of the anomaly taking advantage of its 30 m spatial resolution.

Figure 7. Active lava flow with HYPERION

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Figure 8. Effusion rate obtained using AVHRR (red) and MODIS (blue) data from 1st of June 2008 to 14th of October 2009 - The second class of algorithms regards the analysis of

degassing plumes and eruptive clouds aimed to the estimation of concentration and flux of sulphur dioxide

(SO2), water vapour and volcanic aerosol optical thickness and if present ash content in volcanic plume (Figure 9 and Figure 10)

Figure 9. SO2 Map with MODIS

Figure 10. Aerosol optical Thickness Map with ASTER

Figure 11 shows the SO2 flux obtained with ASTER and MODIS and compared with the COSPEC network for what concerns the 2008 event. The not correspondence of satellite data and ground network is due to different time acquisition and different bands of computation and different speed wind during the acquisitions. Anyway the SO2 results retrieved by EO data can be considered comparable with the NON EO data.

Figure 11. SO2 flux measured with ASTER(cyan box), ASTER (green

triangle) and COSPEC network (red cross)

4.3 ASI-SRV: Post crisis phase

ASI-SRV foresees the generation of significant information also for the definition of the new lava and ash cover distribution after the end of an eruption (Figure 12).

Figure 12. Lava distribution Map

Together with these products the deformation map by using SAR data has been produced . 4.4 ASI-SRV products validation

The generation of the products obtained by these algorithms is validated through ground networks of instruments which contribute to their validation. Main data are the GPS data, levelling network and SO2 flux (Caltabiano et al., 1994) (Figure 13,Figure 14, Figure 15).

All the validated ASI-SRV products generated by the data processor software are stored in the ASI-SRV main database, in order to be published on the dedicated WebGIS and then made available to the user

Figure 13. Levelling network

Figure 14. GPS, in red, and SO2 station, in green

Figure 15. Deformation velocity map (down) and the validation with GPS station (Campi Flegrei –Vesuvio site) (up)

5. CONCLUSION

The SRV Project, funded by the Italian Space Agency (ASI) in the frame of the National Space Plan 2003-2005 under the Earth Observations section for natural risks management, is devoted to the development of an integrated system based on EO and NON EO data to respond to specific needs of the Italian DPC and improve the monitoring of Italian active volcanoes during all the risk phases (Pre Crisis, Crisis and Post Crisis).

In this work main results obtained during the lifetime of ASI-SRV project have been showed. All the validated ASI-SRV products generated by the data processor software have been stored in the ASI-SRV main database, in order to be published on the dedicated WebGIS and then made available to the user.

5.1 References

Berardino P., Fornaro G., Lanari R., Sansosti E., “A new Algorithm for Surface Deformation Monitoring based on Small Baseline Differential SAR Interferograms”, IEEE Transactions on Geoscience and Remote Sensing, Vol. 40, No. 11, pp. 2375-2383, November 2002 Bertacchini E., Teggi S., Musacchio M., Buongiorno M.F. Correzioni Atmosferiche e Topografiche di immagini satellitari nell’ambito del progetto Sistema Rischio Vulcanico Atti 11a Conferenza Nazionale ASITA 2007 Caltabiano T., Romano R., Budetta G.,” SO2 flux measurements at Mount Etna (Sicily)”. Jour. Geoph. Res., 99, D6, 12.809-12.819, 1994. Gillespie A., Rokugawa S., Matsunaga T., Cothern JS, Hook S., and Kahle AB., “ A temperature and emissivity separation

algorithm for Advanced Spaceborne Thermal Emission and reflection Radiometer (ASTER) images”, IEEE Trans. Geosci. Remote Sens., 36: 1113-1126., 1998 Lombardo V., Buongiorno M.F., Merucci L., Pieri D.C., “Differences in Landsat TM derived lava flow thermal structure during summit and flank eruption at Mount Etna”, Journal of Volcanology and Geothermal Research, 134/1-2:15-34, 2004 Pugnaghi S., Gangale G., Corradini S., Buongiorno M.F. (2006), Mt Etna sulfur dioxide flux monitoring using ASTER-TIR data and atmospheric observations, Journal of Volcanology and Geothermal Research, 152, 74–90 Realmuto V.J.,”Separating the effects of temperature and emissivity: emissivity spectrum normalization”, in Proc. 2nd TIMS Workshop, JPL Publication, 90-55, Jet Propulsion Lab., Pasadena, CA.,1990 Spinetti C. and M.F. Buongiorno,.”Volcanic Aerosol Optical Characteristics of Mt. Etna Tropospheric Plume Retrieved by Means of Airborne Multispectral Images”. Journal of Atmospheric and Solar-Terrestrial Physics Volume 69, Issue 9, pp. 981-994 doi:10.1016/j.jastp.2007.03.014, 2007 Teggi S., Musacchio M., Buongiorno M. F., Procedura con interfaccia-utente grafica per le correzioni atmosferiche di immagini satellitari, Atti della 9a conferenza nazionale ASITA 2005 5.2 Acknowledgements

This study was supported by Agenzia Spaziale Italiana Progetto Sistema Rischio Vulcanico project (ASI-SRV ref ASI I/091/06/0). Many colleagues have contributed with useful comments, punctual information and in data treatment. Their list would be simply too long but they are not less important for this project and for the Italian research.