【正文】 039。239。239。039。139。139。039。039。039。UTF839。 in addition the user can visualize the effect of every change imposed on it. Geomatics is a sector that depends on images to such an extent that one could tell that images are the most valuable geodata sources. Feature extraction from a raster image is a very mon task for geographical anizations around the world. Through the bination of image information and SVG code instead of vector data, digitization can produce scalable vector data (., point, line, polyline, polygonetc. elements) or GML (Geography Markup Language) encoded data. Moreover, the need for visualization of the new ponents introduced by GML specification, such as Grid functions, requires the rendering of continuous data in XML (Antoniou and Tsoulos, 2021). Another area that will be influenced due to the evolution of open standards is interoperability. Provided that each satellite sensor stores data in its own format, the same applies to proprietary software, which also uses ‘‘closed’’ formats. The efficiency of remote sensing applications and interoperability can be enhanced with the use of open standards. By storing a raster dataset in an XMLencoded format, the information included in the dataset is conveyed intact along with the advantages that open standards bear. This paper elaborates on the technological environment, which can be utilized for the XML encoding of raster images and the extraction of information from the resulting datasets using open source methods. 2. Technological background . Extensible markup language—XML XML stands for Extensible Markup Language and it is a W3Cendorsed standard for document markup. XML describes a class of data objects called XML documents and partially describes the behavior of puter programs that process them. XML documents are made up of storage units called entities, which contain either parsed or unparsed data. Parsed data are made up of characters forming character data or markup. Markup encodes the description of the document’s storage layout and logical structure. Furthermore XML provides a mechanism to impose constraints on the storage layout and logical structure (Bray et al., 2021). XML is a metamarkup language implying that it enables the user to create his/her own tags according to the application’s needs. That means that XML does not have a fixed set of tags and elements that cover the needs of every application or user. Markup in an XML document describes the structure of the document along with the document’s semantics. XML allows the developers to define properly the elements required and to encode their associations. XML defines the syntax that markup languages of each knowledge domain, such as MusicML, MathML, GML and SVG must follow. Although it is quite flexible in the elements’ definition, it is rather strict in many other aspects. It provides grammar rules for the XML documents describing their proper structure, which allows for the development of XML parsers that can read any XML document. Documents that satisfy this grammar are considered as well formed (Elliotte and Means, 2021). . Geography markup language—GML GML is a markup language used to encode and integrate spatial information, spatial relationships and nonspatial information, especially when nonspatial data are XMLencoded. GML also aims to serve both data transport and data storage, in a widearea Inter context. GML exploits W3C standards to encode geographic information that can be readily shared in the Inter. In addition, GML provides a set of mon geographic modeling objects to enable interoperability of independently developed applications. It is designed to support interoperability and does so by providing basic geometry tags, a mon data model and a mechanism for creating and sharing application schemas. Although it is not the first metalanguage introduced to describe geographic information, it is the first that has been widely accepted by the GIS munity. An important characteristic of GML inherited from the XML specification is that it separates spatial and nonspatial content from presentation (Galdos, 2021). . Scalable vector graphics—SVG SVG stands for Scalable Vector Graphics, an XML grammar for stylable graphics used as an XML namespace. SVG is a language for the description of twodimensional graphics in XML and allows for the encoding of three types of objects: vector graphics, images and text. Graphic objects can be grouped, styled, transformed and posed into previously rendered objects. The feature set includes nested transformations, clipping paths, alpha masks, filter effects and template objects, which are applied during rendering. In general, SVG drawings can be interactive and dynamic. Animations can be defined and triggered either declaratively or via scripting (Ferraiolo, 2021). SVG graphics are scalable to different display resolutions. The same SVG graphic can be displayed at different sizes on the same Web page and reused at different sizes on different pages. SVG graphics are scalable because the same SVG content can be a standalone graphic or can be referenced or included in other SVG graphics, thereby allowing a plex illustration to be built up in parts, perhaps by several people. During rendering SVG also provides clientside raster filter effects so that moving to a vector format does not result to the loss of popular effects such as soft drop shadows (Ferraiolo, 2021). Other characteristics of SVG include a smaller file size and searchable text information. An SVG file—utilizing the elements provided by the specification—is usually smaller than a raster file for the same map resolution and thus can be transferred across the Inter more quickly. Text information inside SVG is still text and