Autodesk 15606-011408-9320 User Guide - Page 172

key An alphanumeric character string or an integer used to uniquely identify a map feature or a record in an attribute table. You can form explicit or implicit links between spatial features in an SDF file and records in an attribute table using a common key. See also primary key. latitude/longitude coordinate system A global coordinate system in which locations are expressed by geographical coordinates (the geodetic latitude and longitude) that depict angular measurements relative to the Earth's ellipsoid. These coordinates are often expressed in decimal degrees or degrees° minutes' seconds". layer See map layer. layer group A collection of related map layers. You create layer groups in Autodesk MapGuide Author. legend A key to or an explanation of the symbols in a map, and their meaning or values. In the Autodesk MapGuide Author View tab and in Autodesk MapGuide Viewer, you can use the legend to turn layers on and off so that the map features they contain are no longer visible or selectable. line A drawing entity with start and end coordinates connected by a single straight line. Lines typically represent the shape of map features too narrow to be displayed as an area at the given scale (contours, street centerlines, or streams), or linear features with no area (county boundary lines). line spacing ratio The ratio of the distance between lines of text to text character height. For example, if the distance between lines of text is 10 mm, and the line spacing ratio is 0.5, the font height is 20 mm. linetype A property of a line that defines its appearance. Examples of linetypes include continuous, dashed, and dotted. linked table or database A table or database linked to a layer using Autodesk MapGuide Author. The records in the table are linked to the spatial features in the layer via common keys. map An abstract representation of the physical features of a portion of the Earth's surface graphically displayed on a planar surface. Maps display signs, symbols, and spatial relationships among the features. They typically emphasize, generalize, and omit certain features from the display to meet design objectives. For example, railroad features might be included in a transportation map but excluded from a highway map. map feature Any spatial feature on a map. In the Autodesk MapGuide products, map features can be points, polylines, polygons or text. Although raster images are technically not map features, you can display them in raster layers. map layer A grouping of map features that are stored and displayed together. Individual map layers can be turned on and off to show or hide the features they contain. When all map layers are displayed, they overlap like transparencies and show all features in the map. map projection The representation of the Earth, which is curved, on a flat map surface. A map projection defines the units and characteristics of a coordinate system. The three basic types of map projections are azimuthal, conical, and cylindrical. 172 | Glossary