A web based GIS archive for local area hazard prevention and mitigation

1. A web based GIS archive for local area hazard prevention and mitigation E. Costamagna Department of Electronics,University of Pavia, Italy

2. Outline • Introduction • Motivations of the project • Objectives • Web-based GIS archive • Examples of data analysis • Future implementations • Conclusions

3. Data fusion over urban environments • Advantages • more information available • fusion at different levels • more precise characterization • "intelligent" analysis • Problems • what is relevant to what? • different resolution • different noise • different (in)accuracy • Challenges • efficient and robust algorithms • (semi)automatic analysis • self-adapting systems • "intelligent" analysis

4. Data analysis for local area hazard mitigation • The use of images and Geographic Information Systems (GIS) for disaster management is now an extremely interesting topic. • We may use aerial images, LIDAR data, but also satellite images to monitor floods, earthquakes and other events. • By this way, it is possible to obtain a complete view of the phenomena, with a clear idea of the interested area.

5. Motivations of the project • The use of images and Geographic Information Systems (GIS) for disaster management is now an extremely interesting topic: • to fuse data coming from different sources, • for the capacity to build systems able to cope with catastrophic events efficiently and in short time. • Different events correspond to different spatial and temporal scales, with a suitable approach even if based on the same (or at least very similar) information.

6. The town of Pavia, Italy • Pavia, Northern Italy, is crossed by Ticino river and not far from the Po, the major Italian river. • The city of Pavia can be inundated by Ticino floods or, more often, by Po backwaters, since Pavia is located not far away from the confluence of the two rivers. • During the last decade Pavia was partially flooded four times: these floods caused a few casualties and relevant damages to bridges and other important buildings.

7. Objectives • The aims of this research work are: • a detailed analysis of already happened catastrophic events by means of satellite images to define a database of the damages areas or buildings, and to develop suitable risk maps; • the definition and realization of a Geographic Information System for the storage of all these information (and future ones also), based on the analysis of images of the same zone; • some preliminary results of algorithms devoted to data fusion with respect to different sensors, and also different sources of spatial and temporal information; • a first definition of a support system for aid in case of catastrophic events.

8. Possible synergies • The project aims • to define and realize a synergy among the different competencies in remote sensing data analysis already present in the University of Pavia • to strengthen the collaboration between these teams and the civil protection. • This project tries to define a common framework, with the definition of what each research unit is able to provide and the possible methodologies for the interaction. Its impact and its importance, however, want to be related practically to the development of an integrated GIS and a public available web site. It is clear to all the advantage that this result will bring in terms of a better efficiency in information spreading and accessibility.

9. The web-based archive • Data sets are deposited in a distributed archive on different machines, while the central database management section, based on the map server already described, maintains a repository of metadata regarding each set. • The metadata contains information about the geographical area covered by the image, data characteristics (in terms for instance of sensor type, data quality, ground resolution, data type, …).

10. Available data sets • Cartographic sources (1:10000, 1:2000, 1:500) • LIDAR data (two sets) • Aerial photographs • AIRSAR polarimetric SAR images • SIR-C/X-SAR radar images (from Shuttle) • ERS data (radar from satellite) • KVR-1000 images (visible from satellite) • SRTM data • LANDSAT images • ENVISAT SAR and optical data

11. LIDAR data • A first LIDAR data set has been acquired on the town of Pavia and its immediate neighborhood in mid-November 1999 with the Toposys sensor, able to acquire, approximately five points per square meter. • A second LIDAR data set is available, obtained during a second flight campaign in December 1999, and acquired by an Optech ALTM 1210 sensor, able to measure, for each emitted laser pulse, the first pulse, the last pulse and also their intensities.

12. LIDAR data characteristics Toposys Optech

13. The map server • We used Autodesk MapGuide, rel. 4: • it is able to serve on the net vector and raster graphic data, as well as database data linked with them; • it is able to read directly raster data format, such as TIFF, GeoTIFF, JPG, BMP, PNG and GIF; • they can be georeferenced by means of a, so-called, world file (for GeoTIFF file the world file is not necessary, of course). • it is equipped with quite a universal format converter, able to read the main GIS formats such as: Intergraph DGN, ESRI Shape (SHP) and coverage, MapInfo MIF/MID, Autocad 14 DXF and DWG.

14. System capabilities • We may obtain • a few information about the town of Pavia and its neighborhood; • the recent history of the town in term of disasters and hydro-geological problems related with the site; • a description of the different data sets contained in the digital archive; • some applications and researches already carried on by the groups referring to this project using part of the archive; • the archive portal.

15. Mapserver capabilities • Access limitation by user or users’ group • Visualization of all the available data sets • Visualization of a unique name to individuate each sub-set for subsequent retrieval • Database examples retrieval • Spatial query of the database • Query by application

16. LIDAR and optical data joint analysis • DTM generation from laser scanning data implies essentially that laser echoes generated by natural objects not belonging to the ground, such as trees, are eliminated; at the same time it is also necessary to filter out echoes coming from man-made objects, such as buildings. • The detection and classification capabilities of the optical measurements may be improved by exploiting the higher ground resolution of LIDAR measurements, especially if both the first and the last pulse are available.

17. Some results over Pavia • The aerial image provides more details, allowing to discriminate between garden paths and green areas at the terrain level, while LIDAR data is extremely useful to separate the buildings from the background. • The roof of the major building (Collegio Borromeo), due to the different position of its parts with respect to the sun, is differently classified if the aerial data alone is considered. This was fixed using LIDAR data.

18. Challenges • The actual structure of the site lacks a few critical issues, that need to be addressed in the near future. • First of all, due to different data politics among all the structures that provided data to the common GIS, it is necessary to amalgamate the viewpoints and try to define a common playground for actors working on the political, research and civil protection sides. • Second, more of the “a priori” knowledge about data importance and usefulness for specific application should be translated into the database, to promptly and timely guide the user to the information he/she is looking for (or, at least, the data from which extract these info).

19. Conclusions and future implementations • This work shows the tremendous possibilities provided by a GIS archive of remote sensed data. • Future implementation will take into account the possibility to provide interactively the data sets referring to a given location, taking into account the “a priori” knowledge of the experts belonging to the project to give a sort of pre-selection among all the data. • Many analyses on the data will also be considered, starting from three-dimensional urban structure extraction.