1.. _vector.nas:
2
3NAS - ALKIS
4===========
5
6.. shortname:: NAS
7
8.. build_dependencies:: Xerces
9
10The NAS driver reads the NAS/ALKIS format used for cadastral data in
11Germany. The format is a GML profile with fairly complex GML3 objects
12not easily read with the general OGR GML driver.
13
14This driver depends on GDAL/OGR being built with the Xerces XML parsing
15library.
16
17The driver looks for "opengis.net/gml" and one of the strings semicolon
18separated strings listed in the option **NAS_INDICATOR** (which defaults
19to "NAS-Operationen;AAA-Fachschema;aaa.xsd;aaa-suite") to determine if a
20input is a NAS file and ignores all files without any matches.
21
22In GDAL 2.3 a bunch of workarounds were removed, that caused the driver
23to remap or ignore some elements and attributes internally to avoid
24attribute conflicts (e.g. *zeigtAufExternes*). Instead it now takes the
25**NAS_GFS_TEMPLATE** option, that makes it possible to cleanly map
26element paths to feature attributes using a GFS file like in the GML
27driver. Multiple geometries per layer are also possible (eg.
28ax_flurstueck.objektkoordinaten next to the regular wkb_geometry).
29
30A `GFS
31template <https://github.com/norBIT/alkisimport/blob/master/alkis-schema.gfs>`__
32and a corresponding `PostgreSQL
33schema <https://github.com/norBIT/alkisimport/blob/master/alkis-schema.sql>`__
34of the full NAS schema are part of `norGIS
35ALKIS-Import <http://www.norbit.de/68/>`__ (also featuring a shell
36script and PyQt frontend which ease the import). The two files were
37generated using `xmi2db <https://github.com/norBIT/xmi2db/>`__ (fork of
38`xmi2db <https://github.com/pkorduan/xmi2db>`__) from the official
39application schema.
40
41New in 2.3 is also the option **NAS_NO_RELATION_LAYER** that allows
42disabling populating the table *alkis_beziehungen*. The information found
43there is redundant to the relation fields also contained in original
44elements/tables. Enabling the option also makes progress reporting
45available.
46
47This driver was implemented within the context of the `PostNAS
48project <http://trac.wheregroup.com/PostNAS>`__, which has more
49information on its use and other related projects.
50
51Driver capabilities
52-------------------
53
54.. supports_georeferencing::
55
56.. supports_virtualio::
57