VFK - Czech Cadastral Exchange Data Format
Driver short name
This driver reads VFK files, i.e. data in the Czech cadastral exchange data format. The VFK file is recognized as an datasource with zero or more layers.
The driver is compiled only if GDAL is built with SQLite support.
Points are represented as wkbPoints, lines and boundaries as wkbLineStrings and areas as wkbPolygons. wkbMulti* features are not used. Feature types cannot be mixed in one layer.
This driver supports georeferencing
This driver supports virtual I/O operations (/vsimem/, etc.)
Starting with GDAL 2.3, the following open options can be specified
(typically with the
-oo name=value parameters of ogrinfo or ogr2ogr):
SUPPRESS_GEOMETRY=YES/NO (defaults to NO). Setting it to YES will skip resolving geometry. All layers will be recognized with no geometry type. Mostly useful when user is interested at attributes only. Note that suppressing geometry can cause significant performance gain when reading input VFK data by the driver.
FILE_FIELD=YES/NO (defaults to NO). Setting it to YES will append new field VFK_FILENAME containing name of source VFK file to all layers.
Several configuration options are available.
The driver uses SQLite as a backend database
when reading VFK data. By default, SQLite database is created in a
directory of input VFK file (with file extension ‘.db’).
The user can define DB name with
configuration option. If
configuration option is given, the driver overwrites existing SQLite
database and stores data read from input VFK file into newly created DB.
OGR_VFK_DB_DELETE =YES configuration option is
given, the driver deletes backend SQLite database when closing the datasource.
Resolved geometries are stored also in backend
SQLite database. It means that geometries are resolved only once when
building SQLite database from VFK data. Geometries are stored in WKB
format. Note that GDAL doesn’t need to be built with SpatiaLite support.
Geometries are not stored in DB when
configuration option is given. In this case geometries are resolved when
reading data from DB on the fly.
Internal working and performance tweaking
If backend SQLite database already exists then the driver reads features directly from the database and not from input VFK file given as an input datasource. This causes significant performance gain when reading features by the driver.
The driver reads by default all data blocks from VFK
file when building backend SQLite database. When configuration option
OGR_VFK_DB_READ_ALL_BLOCKS =NO is given, the driver
reads only data blocks which are requested by the user. This can be
useful when the user want to process only part of VFK data.
Datasource name is a full path to the VFK file.
The driver supports reading files managed by VSI Virtual File System API, which include “regular” files, as well as files in the /vsizip/, /vsigzip/, and /vsicurl/ read-only domains.
Since GDAL 2.2 also a full path to the backend SQLite database can be
used as an datasource. By default, such datasource is read by SQLite
driver. If configuration option
is given, such datasource is opened by VFK driver instead.
VFK data blocks are used as layer names.
An internal SQL engine is used to evaluate the expression. Evaluation is done once when the attribute filter is set.
Bounding boxes of features stored in topology structure are used to evaluate if a features matches current spatial filter. Evaluation is done once when the spatial filter is set.