The IDRISI Vector Format Reader and Writer modules allow FME to read and write IDRISI vector files. IDRISI files use a published binary format. The IDRISI data and the documentation file structure are described in the IDRISI Guide to GIS and Image Processing, Volume 1.
Overview
IDRISI is a geographic information and image processing software system that is widely used by universities worldwide. It is a two-dimensional (2D) system which allows user-defined attributes stored in an Access database to be linked to its data file.
IDRISI features contain a feature geometry and an id number. An IDRISI file consists of at least two physical files, having the following filename extensions:
|
Filename Extension |
Contents |
|
.vct |
Vector data file |
|
.vdc |
Vector documentation file |
If an Access database is available, the following files should also be available:
|
Filename Extension |
Contents |
|
.vlx |
Vector link information file |
|
.mdb, .accdb |
Access database file |
|
.adc |
Attribute documentation file |
These extensions are added to the basename of the IDRISI file.
The IDRISI reader and writer support the storage of point, line, area (polygon), and text geometric data in the .vct files.
The FME considers an IDRISI dataset to be a collection of IDRISI files in a single folder.
Reader Overview
The IDRISI reader first scans the file or folder specified in the Reader Dataset parameter.
For each IDRISI file that it finds, FME checks to see if that file is requested by looking at the list of feature types specified when the workspace was created. If a match is made or no feature types were specified in the workspace, the IDRISI file is opened.
The IDRISI reader then extracts features from the file one at a time, and passes them on to the rest of the FME for further processing. If an additional Access database is available, the user-defined attributes will also be passed to the FME. When the file is exhausted, the IDRISI reader move on to the next file in the folder.
Writer Overview
The IDRISI writer creates and writes feature data to IDRISI files in the folder specified by the Writer Dataset parameter. As with the reader, the folder must exist before the translation occurs. Any old IDRISI files in the folder having the same name as files being written are overwritten with the new feature data. As features are routed to the IDRISI writer, the IDRISI writer determines the file into which the features are written to and outputs them accordingly. Many IDRISI files can be written during a single FME session.
In IDRISI, each vector file can have only one type of feature. Any feature not matching the feature type as specified in the mapping file will not be written to file. In addition, any user-defined attributes are written to the database only if an Access database is available.