Introduction
Beja is a generally flat area with some gently undulating hill regions in the north. Beja falls within the Alentejo province which has been recognised by experts to be an area of high land degradation risk (Seixas 2000). Alentejo is an important regional economic area, with current mining activities extracting copper, silver, lead and zinc. However the Alentejo is predominantly an agricultural area, yielding over 80% of Portugal's total wheat production (Gouveia and Trigo 2008). Annual crops include winter wheat, barley, maize and sunflower. Annual crops are rotated with fallow ground and stock pasturing (Seixas 2000). The region also supports large areas of permanent crops, na mely olives, cork oaks and grapes. Many of the permanent cork and olive groves are mixed with annual cropping.
Much of the land in Alentejo has recently been bought over by Spanish land owners with the intention of converting land that is traditionally used for annual cropping to permanent crop cover. Extensive olive and grape plantations have replaced much of the wheat, maize, sunflower and barley crops. Additionally, there has been a vast increase in the amount of irrigation (both legitimate and illegal) applied to crops, aiming to increase productivity. Cork forests are native to the country and are economically valuable to the region, as Portugal is the largest producer of cork used for wine bottling in the world (Bugge 2008). Cork (Quercus suber) trees are also an important barrier to desertification on the Iberian Peninsula (Bugge 2008). Holm oaks (Quercus rotundifolia) are another major native forest constituent, while the remaining forest is comprised of eucalyptus and Maritime pine timber plantations (PortugalWeb 2009). Both cork and Holm oak forests have very open canopies, and in some areas could be considered woodland areas rather than forest, as the trees are very sparsely distributed with grassy understories. On the other hand, pine and eucalypt plantations have nearly closed canopies and are generally monocultures.
Temperature
The Alentejo experiences typically Mediterranean climate and is generally warmer than the rest of the country. Temperatures can reach 40°C in the summer, usually during July and August. The winter is quite mild with minimum temperatures around 5°C.
Precipitation
The mainland of the Iberian Peninsula (Portugal and Spain) experiences two main precipitation types which are strongly linked to seasonality: convective in the summer and frontal in the winter (Serrano, Garcia et al. 1999). The region of Alentejo receives less rainfall than the national average for Portugal. The mean annual rainfall of the area is approximately 580 mm (Seixas 2000), with the highest amount of rain falling in December. The wet season is between the months of October and April, and 85% of the total annual rainfall occurs during this period.
The yearly mean ratio between rainfall and potential evapotranspiration is 0.42; which decreases to 0.05 in the spring, indicating serious hydrological stress conditions for vegetation growth (Seixas 2000).
Open specifications for web-based GIS
The open specification provides information about a given specification as well as specific programming rules and advice for implementing the interfaces and/or protocols that enable interoperability between systems (Moreno-Sanchez et al. 2007).
The Open Geospatial Consortium, Inc. (OGC) is a non-profit, international, voluntary consensus standards organization that is leading the development of standards for geospatial and location based services.
OpenGIS is a Registered
Trademark of the OGC and is the brand name associated with the Specifications and documents produced by the OGC. OpenGIS Specifications support interoperable solutions that “geo-enable” the Web, wireless and location-based services, and mainstream IT. The specifications empower technology developers
to make complex spatial information and services accessible and useful with all kinds of applications.
Most of the OGC standards are based on a generalized architecture captured in a set of documents collectively called the Abstract Specification, which describes a basic data model for geographic features to be represented. Atop the Abstract Specification are a growing number of specifications, or standards, that have been (or are being) developed to serve specific needs for interoperable location and geospatial technology, including GIS. Most of well-known specifications are the Web Map Service (WMS), the Web Feature Service (WFS), and the Web Coverage Service (WCS). Figure 2 indicates the relationships among some specifications provided by OGC.
WMS provides a simple HTTP interface for requesting geo-registered map images from one or more distributed geospatial databases. A WMS request defines the geographic layer(s) and area of interest to be processed. The response to the request is one or more geo-registered map images (returned as JPEG, PNG, etc) that can be displayed in a browser application. The interface also supports the ability to specify whether the returned images should be transparent so that layers from multiple servers can be combined or not. Therefore, it allows for a smooth integration of different (raster or vector) maps in web mapping applications over the Internet (Schütze 2007).
Open source software for web-based GIS
Open source software are programs whose licenses give users the freedom to run the program for any purpose, to modify the program, and to freely redistribute either the original or modified program without further limitations or royalty payments. There are many open source software available to develop the webbased GIS. The descriptions on software below are some of them selected to be used in the prototype.
Geoserver
GeoServer is an open source software server written in Java that allows users to share and edit geospatial data. Designed for interoperability, it publishes data from any major spatial data source using open standards. GeoServer is the reference implementation of the WFS and WCS standards, as well as a high performance certified compliant WMS. GeoServer forms a core component of the Geospatial Web. Compared to the MapServer, GeoServer supports the most of GIS functions rather than only publish spatial data. In order to make sure the extendibility of the prototype, the GeoServer is preferred, though limited GIS functions are needed now.
Maps are relatively static, and do not change very often. As most mapping clients render WMS data every time they are queried, this can result in unnecessary processing and increased waiting time. GeoWebCache optimizes this experience by caching map tiles as they are requested, in effect acting as a proxy between
client such as OpenLayers and server such as GeoServer, or any WMS-compliant server. As new maps and tiles are requested, GeoWebCache intercepts these calls and returns pre-rendered tiles if stored, or calls the server to render new tiles as necessary. Thus, once tiles are stored, the speed of map rendering increases many times, making for a more seamless user experience. The primary purpose to use GeoWebCache is to reduce the response time of the prototype.
PostgreSQL
often simplyPostgres, is anobject-relational database management system(ORDBMS).It is released under aBSD-style licenseand is thusfree and open source software. As with many otheropen sourceprograms, PostgreSQL is not controlled by any single company, but has a global community of developers and companies to develop it.(Wikipedia.org)
