session - EC GI & GIS Portal

SESSION METADATA AND CATALOGUES
Mapping agencies have a normalized symbolization system for each one of their series or products. If this
capability is made accessible to the public through an Internet Geo-service, any user – with or without
cartographic knowledge – could provide his/her maps with the standardized, normalized symbology designed
by these agencies.
The lack of a service storing, managing, structuring and providing access to this symbology has been detected.
Its existence would facilitate the provision of visually appropriate maps to a host of scientific professionals in
the fields of geology, communications, farming, environment or any other where the creation of mapping
documents is necessary.
For this reason the creation of a style repository-catalogue is proposed providing users with the symbology
corresponding to every style normalized by the different mapping agencies in their cartographic series… We
also propose that this catalogue should provide users with a searching service allowing them to locate and
select the style best suited for their needs
2. Loss of cartographic quality in maps obtained from WMS.
The numerous advantages offered by WMS in obtaining maps contrast with a great inconvenience, namely the
lack of cartographic quality of the rasterized vector maps obtained through these agencies. In order to resolve
this drawback, the possibility of application of the SLD Specification to customize maps may be taken
advantage of. Nevertheless the manual preparation of an XML document consistent with the SLD
Specification by any user involves the following obstacles:
On the one hand, the lack of knowledge about graphic semiotics. This type of knowledge deals with some
aspects of geographic information (qualitatively, quantitatively, in an ordered manner), it also deals with the
way the information is distributed (continuous, discrete) and with the visual perception of the information
(visual variables and perceptive properties thereof). In addition, it concerns other aspects external to
geographic information, such as scale, purpose and thematic type to be represented, among others. In order to
decide about symbolization of each geographic feature best suited for a particular map, all the consideration
above should be taken into account. Furthermore, symbology should be aesthetically integrated as a whole.
On the other hand, SLD document-making process turns out to be very tedious. These documents model and
assign parameters to the symbolization styles (they define colours, weights, fonts… for each symbology in a
structured way) by means of XML. WMS users needn’t have that much knowledge!
Therefore these considerations have led us to propose a style repository-catalogue providing users with the
SLD document properly built from the style normalized by a mapping agency, the particular style being
chosen by users themselves. This way you would have to simply download the style from the repository,
directly applying it on a desktop GIS-SDI or through a WMS to get the styled map.
Objective
The objective sought is the creation of a style repository-catalogue providing SDI users with the styles
normalized by the different mapping agencies which, when applied to the WMS, give rise to normalized or
regulated maps in accordance with those agencies.
The styles returned by the catalogue should be provided in several different formats (txt, sld and svg) so as to
enlarge their varied uses and applications:
� txt: For simple descriptive purposes: definition of the chosen symbology style.
� sld: For direct application to WMS to obtain maps.
� svg: Visually provides, as a legend, the style being downloaded.
The repository should act as a catalogue service that provides search and downloading services, conformant to
OGC Specifications.
Style Repository-Catalogue Characteristics
The catalogue will be made up of a Postgres database that will store in relational structured tables the data
defining each style and the agency generating it.
This geoservice (catalogue) will have the capability of interacting with the database as mentioned above in
order to carry out searches, downloading, insertions, updates and deletions. To that end a series of requests will
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