FME can read and write the Swedish FF (FlyttFil) file format.
The FF file format is the export, or transfer file format for exchanging information between applications such as AutoKa-PC and BankIR.
Overview
FF files may contain both two-dimensional (2D) and three-dimensional (3D) features.
FF files store feature geometries as well as several predefined attributes. There is only one user defined attribute. There are 6 kinds of features which are separated into two groups: points, lines, and text are considered simple details, whereas polygons, groups, and clusters are compound details.
By default, FME looks for an extension of .ff for the input FF files, but will accept any FF file as input regardless of the filename or extension. FME considers an FF dataset to be a single AutoKa FF file. FF files are binary files consisting of variable-length binary records or packets which make up individual features or details.
The FF format also contains some metadata, such as the creation date of the original data, a user’s signature, scaling factors, and so forth. However, a wide variety of applications use the FF format to shuttle information back and forth, some of which cannot properly maintain this metadata. The standard solution was to store this metadata in a small partnering text file, usually with the name autoka.par when necessary. FME has adopted this convention and can automatically read and write the appropriate autoka.par parameter file when importing from or exporting to the FF format.
Terminology Notes
Some FF terminology differs from what is used in the majority of other formats. If referring to FF documentation, you may notice some difference in the terminology used in this section.
- FME documentation uses the word polygon in its mathematical definition of a closed region. FF documentation uses the word polygon to refer to an unclosed region, and the word area to refer to a closed region.
- In the FF format, the X axis increases vertically and the Y axis increases horizontally. In contrast, FME defines the X and Y directions to be consistent with mathematics and most other formats: X is the horizontal axis and Y is the vertical axis. FME automatically takes this axis switching into account where necessary, translating the data as it was intended.
Reader Overview
The FF reader simply opens the input file and immediately starts reading features and returning them to the rest of the FME for processing. If directed to do so, the FF reader will produce a partner autoka.par parameter file that contains the relevant metatext found in the FF file. The reader does not have any requirement for definition statements, as there are no user-defined attributes in the FF specification.
If the data being read contains self-intersecting polygons, the Fix self-intersecting polygons parameter in the Reader parameters can be checked (set to Yes) to break self-intersecting polygons into non-intersecting polygons.
Each feature returned has its feature type set to the geometric type of the feature, as follows:
- point
- line
- text
- polygon
- cluster
- group
The first three feature types are simple details and are processed completely by the reader itself. The last three feature types are passed to the rest of the FME with attributes (up-links and down-links) indicating how the compound features may be re-assembled from several other features, but this is not done directly by the reader.
Final processing and construction of the compound features can be done in the workspace if the user desires. By default, FME collects the pieces and construct the compound features completely, flagging any file errors it may encounter.
Writer Overview
The FF writer creates and writes feature data to the FF file specified by the Dataset parameter. Any FF file with the same name is overwritten with the new feature data. Attributes that contain character strings will be written with a fixed encoding that supports the accented characters in the Swedish alphabet (Latin-1).
Polygon Writing
It is important to mention that polygons can be written out in two different methods:
- If a polygon feature is written out with a closed area as its geometry, the topology for this feature will be computed and all the appropriate pieces will be written to the FF file automatically.
- The second method of writing out polygons is to compute the topology before hand and write out each piece separately. In this method, polygons will have no geometry, but will have the appropriate up and down links to the edges and centroid features, as necessary.