As it was mentioned in chapter 62 “Import of data in DXF format” DXF file is a text file of a special format which contains data about features of AutoCAD draft: names of layers, spatial categories of features and descriptions of features themselves. Besides, a string value can be linked with every feature. From the point of view of ObjectLand this value can be considered as a field value of the table linked with features of the present type. Thus, DXF file can contain not only spatial data, but some table data as well. Detailed description of DXF file format is given in manuals on AutoCAD system.
Essential difference of draft structure of AutoCAD from the structure of ObjectLand map is that in AutoCAD there is no notion of a feature type. A draft is made up of arbitrary number of layers, and every layer can contain features of all spatial categories without differentiation to feature types which is the case in ObjectLand.
A layer of AutoCAD draft can also contain blocks. A block is graphics composed of different graphic elements which can be inserted into the draft in several places with indication of a block name, binding point, slope angle and scale. ObjectLand does not have a similar structure, however point features can serve as a kind of analogy to blocks, that is why the possibility of exporting point features of ObjectLand map as blocks of DXF file is provided.
File of DXF format cannot contain image features, that is why image features of ObjectLand map are not exported to DXF format.
To set correspondence between feature types in ObjectLand map layers on the one hand and spatial categories of features and blocks of DXF file layers on the other hand it is necessary to perform export setting.
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