This glossary presents the meaning of relevant terms used in SavGIS©.

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A

Attribute: an attribute is a field containing values for each object belonging to a relation. The attributes are of different types. Nominal attributes contains textual or descriptive values also called categories (land use type, names…). Numerical attributes contains either real values, integers (in the case of satellite bands for example) or RGB colour values (in the case of a colour composite for instance). It is indispensable to set as a nominal attribute the field containing the keys in the Savedit module .

C

Categories: see attribute

E

External view: an external view is a set of selected relations (and eventually a set of selected attributes for each relation) which can be used in the Savane, Savedit and Savamer modules. The possibility to select a restricted number of relations is useful when working on a specific subject which does not require all the relations encompassed in the SavGIS database. The external views are set using the Savateca module.

F

Frame: in the Savane module, the frame is the rectangle visible on the page in which objects are mapped out . When the coordinates window is activated, it indicates the coordinates of the cursor through out the frame.

G

Geo-referencing: process by which the user establish the relationship between an image coordinate system (row, column of pixels) and the coordinates of the real world (e.g. longitude/latitude degrees). The geo-referencing process is performed in the Savamer module using control points. Geo-referencing is associated with another operation called rectification. The rectification is the process by which an image is geometrically transformed. Rectification typically involves rotation and scaling of pixels, and thus requires a resampling of values.

I

Integration: process by which the user adds new objects into the relations in the SavGIS database. Integration is an essential process in SavGIS© and is performed using the Savateca module. Once integrated, the data are protected and cannot be modified or deteriorated in the other modules. Nevertheless, a temporary integration of external data (Excel, Access, DBF) is possible in the Savane module so that the user is able to map out quickly his/her data.

K

Key: a key is a nominal code which identifies an object. Each object has a unique key. In some cases, isolated zones can be grouped and be assigned a unique key (multiple zone object). This is often the case for geological formations or land use maps.

M

Map: in the Savane module, a map is defined by the white page which is by default landscape oriented. The map contains between one and twelve frames. The map includes generally apart from the frame, a caption, a legend, a graphic scale, a north arrow, and sources (set by user). The map corresponds to the final layout and can be printed as it appears on screen.

Map explorer: the map explorer is the dialogue box available in all the SavGIS modules which allows the user to select objects to be mapped out according to one or more attributes available in the database or resulting from a query. The map explorer also allows to set the legend.

Mask: a mask is a geo-referenced graphic object. A mask can be created by digitising on screen or can result from a geometrical process. The most common process is the generation of a mask around objects with a constant width (also called buffer). A mask can be also generated based on a width varying according to a numerical attribute. Some more operations applied on masks are also available in the Savane module (Invert, Dilate, Crop, Skeleton, Intersection, Union, Subtract…). A mask is useful for instance to select objects (selection by location). A mask can also be converted to a relation to perform operations such as geo-aggregation, geo-belong….

Module: SavGIS© is a GIS system made of four modules. Each module is a programme which performs specific tasks. The Savateca module is meant to manage the scheme and to update the SavGIS database with new objects. The Savedit module allows digitising, graphic editing, image semi-automated vectorising and shapefile and GPS points imports. The Savamer module is designed for geo-referencing images and for integrating them into mosaics. The Savane module is intended for elaborating maps, building queries, carrying out spatial analyses, executing geo-processing and performing statistical calculations.

Mosaic: see relation.

O

Objects: objects are geometrical schematisations of geographical entities (building, road, county…). See relation.

R

Rectification: see geo-referencing.

Registration: process by which the user indicates the path and name of the folder containing the SavGIS database files. This operation conducted in the Savateca module is the prime step before being able to use a database in any module. If the SavGIS database contains several mosaic relations, every of them has to be registered separately.

Relation: a relation is a kind of “layer” or “theme” which contains objects. The objects can be location-based or not. The location-based objects are of three different types (points, lines and zones). In this category are also included the mosaics which are image relations constituted of pixels (geo-referenced pictures). The non-location-based relations are tables of values which do not include graphic features (no vector). Nevertheless, they generally contain an attribute which includes the key corresponding to a related geographical entity so that a join is always possible in order to map out values.

S

Scheme: the scheme is the structure of the database organised in relations containing objects described by their attributes. The management of the SavGIS database scheme (relation removing, attribute type setting, attribute name editing…) is achieved exclusively using the Savateca module.

Sheet: a sheet is a tile resulting from a regular division of the geographic space. In a relation, objects are indexed by sheet. A relation contains one or more sheets. The indexation allows the software to retrieve faster an object and the related values (for example, while performing a query on screen in the Savane module)

Statistics explorer: the statistics explorer is the dialogue box in the Savane module which allows the user to perform statistical calculations on the objects of the database. Note: calculations only relate to objects contained in the window - see window.

W

Window: in the Savane module, the window is a view of a given geographic area. The calculations and queries are only applied to the objects located in the window. When opening a session in Savane, the geographic window is delimited by the frame. The geographic window corresponds then to that which was defined at the time of the database creation in Savateca. Its extent generally covers all the geographic objects within a study zone. The geographic window determines the size in metres of the internal pixel. The more the geographic window covers a restricted area, the better the resolution. This has its importance because the size of the pixel directly influences the precision of certain operations (creation of mask, rasterisation, geo-aggregation, numerical stage, skeletonisation...). Note: the user can manually move the edges of the frame. This action does not modify the extent of the geographic window. The user must thus be vigilant. Indeed, by reducing for example the size of the frame, a part of the geographic objects can be hidden but the queries will still be applied to every object located in the geographic window.