Despite
the
very widespread false idea according to which the geodatabases
file
( .gdb ) cannot be read and modified using
tools
within the Esri ArcGIS platform, recent versions of GDAL (and therefore using
applications such GDAL- queQGIS ) are capable
of, effectively, read and extract information from the geodatabases
file
. The geodatabase file format has become
a very common format for storing and exchanging data space
, in particular since it allows the storage
of multiple data layers and that allows the storage of data layers exceeding
the limits of others specifications .
ArcGIS
users, regularly, use geodatabases
file
when the attribute tables exceed the storage capacity
of
a shapefile attribute table ( a DBF file is limited to ~ 2 GB
in size ).
The GDAL users who work with
geodatabases file should
know that GDAL includes henceforward a
very robust open source, read- only driver for the geodatabase format
file
: OpenFileGDB . The specifications
indicate that this driver is
able to, efficiently, read the contents of databases with a large number of
fields, without any dependent proprietary software.
An additional option
allowing
to interact with geodatabases file
using
GDAL is the FileGDB.FileGDB driver dependant on Esri’s File
Geodatabase SDK , but it provides
reading and writing access to geodatabases file. However,
internal tests at geospatial @ UCLA said that for read-only geodatabase
file operations, FileGDB driver can
be
many
orders
of magnitude slower than the OpenFileGDB driver .
Therefore those users who have
to edit, regularly, geodatabases file
should
install and use the FileGDB driver, while users who need
only
to convert the contents of the geodatabase file to
other formats should use the OpenFileGDB
driver.
The QGIS users can read
geodatabases file by
draging
geodatabases, ending with extension.gdb directly in
the layers window. The geodatabase
can
appear
as
a
folder and cannot be selected using the Add vector layers tool in
QGIS. The contents of the geodatabase file
appear
in the layers window , and each layer
can
be
exported
to
another format with the writing support in GDAL, including the
shapefile format.
For large geodatabases
whose
content exceeds the limits of the shapefile specification we
recommend using GDAL ogr2ogr command
line interface to copy the content of a geodatabase
file
directly
to a PostGIS database. Use the following command,
by replacing the bracketed text with appropriate values for
your configuration (the brackets should not be included
in
your
order
):
ogr2ogr-progress – overwrite –
skipfailures -f “PostgreSQL” PG: ” host = localhost user =
dbname [ postgres ] = [ dbname ] password = [password]” “[
pathtofilegdb ]. gdb ” “[ tablename ]”
