Digitization is the process of converting features on a spatial map into digital format. To digitizing, the map must be attached to a digitizing table (digitizer. Before entering data through the digitization process, to consider any information contained on the map and for what purpose the construction of a data base that will be prepared, for the subsequent separation of the data in layers.
With the concept of grouping information or coverage of this layer has a great significance in the management of data bases :
- Assist in organizing features that relate.
- Minimize the number of attributes associated with each feature.
- Facilitate the repair and maintenance of maps, as commonly available data sources are different for each layer.
- Simplifying the map, because the features that relate easily described, labeled (ID) and symbolized.
- Facilitate the process of spatial analysis.
For the purposes of rapid Engineering, which is caused by some data Autocad format (*. Dwg) in addition to the ability of Autocad in editing much faster than the Arc / Info is the use of technology consultant Computer Aided Design (CAD) through AutoCAD MAP and then converted into the format Arc / Info. The results of this digitization has no attribute directly as a representation type of theme elements of geography. This data is just a collection of Object Graphics 2 or 3-D, which is a point (point), line (line / arc), polygon (area) and annotation (text).
To represent the types of themes, elements and sub-element of the actual appearance of geography, as well as to facilitate data management, then the digitized objects are grouped by type of sub-elements and the types of Object Graphics. In the majority of CAD software sub-element of each group is stored in the Topographic Layer Name Layer using a numerical code.
Objects can contain one or more set of elements that form the vertex position of the object geometry of the line. Each vertex has a 2D Cartesian coordinates (X, Y) or 3D (X, Y, Z) or the Geographic Coordinates (φ, λ, h), depending on the input. On this job, almost all results have cartesian coordinates, except for the elements of topography, elevation points and control points / GPS bundle.