IMPLEMENTATION OF A GIS DEDICATED TO MARINE GEOLOGY

Alexandra Helena Morgado

Hidrographic institute - Portuguese Navy - Marine Geology Division (PT)

Looking back, into the past
The Marine Geology Division (MGD) of the Hydrographic Institute (HI) of the Portuguese Navy, as a long background of scientific work (mainly on the last 40 years), but the data collected during that period of time as not been yet organized on a database, and most of it still remains on analogical format.
Thus, until nowadays, all the data acquired was gathered in books, portfolios, dossiers, diskettes and CDRom, and stored on shelves on warehouses of data.
With the new developments perceived on data acquisition technologies and with the growth of the size and type of files acquired with those technologies, as well as the increasing need of relate, validate and exchange data between different research groups, the difficulties that always existed on organizing data for storing and future sharing, started to be unbearable. Something had to be done and quickly!

Living the present
In the last three years the IHPT has made a considerable effort, financial and scientific, on the acquisition and development of a Geographic Information System (GIS), which can answer the needs of an organization with so many areas of interest and responsibilities on the ocean, river and estuary study and cartography. The modelling, construction and feeding of an oracle database and the planning and building of a GIS specially address for MGD, has started only in December of 2002.
Knowing that those are long term projects, due mainly to the enormous amount of data to be processed, it was agreed that old data and new acquired one would be worked on, simultaneously.
The development of new technologies and information systems associated with cartography, mainly the evolution of GIS functionalities on that area of study, lead the Marine Geology Division, to evaluate and determine the eventual GIS benefits associated with the conception, construction and edition of digital sedimentary charts on the Portuguese Continental Shelf.

General studies and visualization on the Continental shelf
Thus, and as a first approach, the MGD started an experimental project with the elaboration of the digital sediment chart of the Portuguese continental shelf between the estuaries of the Tagus river and Sado river (Figure 1). The planning of this Chart started with the definition of the three main objectives to pursuit:

1. to elaborate the digital sediment chart of the chosen area of study;
2. to integrate data from different nature and origin, obtained during several surveys (e.g.: CTD and nefelometry profiles )
3. and finally, to determine if a GIS is, in fact, a useful tool to elaborate digital sediment cartography.

The sedimentological data, as well as the CTD and nefelometry profiles were sampled on six scientific cruises, between July'1993 and December'1995.
During the field work, samples of unconsolidated superficial sediments were collected. In laboratory grain-size analysis were performed and samples were classified. In order to measure the temperature, density, salinity and turbidity along the water depth, some CTD and nefelometry vertical profiles were performed.
All this data was then organized on a database and imported into the GIS software. The data was work upon with the use of the available GIS functionalities, which allowed its full integration and 3D visualization (Figure 1).
The elaboration of this chart was enlightening on GIS capabilities for sedimentological cartography, especially in what concerns:

• the automatization of compilation and organizational procedures;
• the benefits of digital storing of all data and information;
• the easy visualization and manipulation of individual data as well as integrated data on a geographic scenario or a database;
• the fastness and effectiveness on updating, integration and modelling operations of data and/or information with different origins, formats and coordinate systems.

Figure 1 - Digital sediment chart of the continental shelf between the estuaries of the Tagus river and Sado river

Multidisciplinary studies and visualization on the littoral dynamics
Another important scientific work that has been developed in the last year on the MGD, regards the impact of a harbour (builded in a natural cape) in the longshore sediment transport. The case study is the Sines Cape (southwest of Portugal). Due to its complexity, processes were analysed based on a multidisciplinary approach which include different type of data acquisition. Thus, during the planning of the project, some important aspects concerning the type of data to collect, time and place of sampling and the best formats for storing and manipulate data on the GIS, were considered:

a) The sets of data collected involved multibeam scanning for bottom morphology analysis, sediment sampling for granulometric and composition determinations, current measurements and meteorological data;

b) The different kinds of data were collected in the same period of time. Sampling was carried out on Winter, Spring and Summer of 2003;

c) Four different areas of study were chosen: one located north of Sines Cape, one on the Sines Cape and two located south of that Cape. The sample locations are distributed along a cross shelf profile from the inner shelf and adjacent beach during the months of January, March and September of 2003 and only at beach on June of 2003;
d) Although different types of data were colleted in different formats (different software's of acquisition), the final result was a set of files with formats readable by the GIS software.

The GIS platform (Figure 2), which integrates the information allows systematic updates whenever there is new data to attach and turns into a useful tool for planning new campaigns and/or projects on that area.

Walking forward, towards the future
For all that as been described, it is obvious the importance of GIS capabilities and functionalities on marine scientific maters. Although, we are still at the beginning of a long journey, the importance of this tools is fully recognized. There is a true willing to discover and achieve new and larger objectives specially when there is a huge amount of data to be processed in parallel with the new incoming one.
The next step to unveiling and perceive the benefits of GIS on this and other scientific subjects will necessarily involve the use of remote sensing data, related radar and laser scanning.

Figure 2: Study areas of the project "Influence of the Sines Cape on the littoral sediment transport"