1) Introduction.

lfp2pgsql is a small, commandline, application to parse a Land Form 
Panorama[1] DXF file as released by the UK Ordnance Survey under their 
Opendata program[2] and load the data into a Postgres/PostGIS database.  
The application is modelled on shp2pgsql[3] and builds upon initial work 
by Nick Whitelegg[4][5].

2) Compiling

You have probably got this code by checking out a git repository so you will
need to perform the following commands:

        autoreconf --force --install
        configure
        make
        make install

Full build documentation can be found in the INSTALL file.

3) Usage

Running the program is as simple as:

        lfp2pgsql nn00.dxf contours

This will print SQL statements to standard out which will create a new table
called contours and then insert all of the features from the DXF file into
the contour table.  You can pipe the SQL directly into the psql command, 
assuming you already have a database called opendata:

         lfp2pgsql nn00.dxf contours | psql -d opendata

lfp2pgsql accepts a number of flags to modify the SQL output.  If you want 
to delete the table and start again use the -d flag:

         lfp2pgsql -d nn00.dxf contours | psql -d opendata

The -a flag creates SQL statements to insert additional data into an existing
table, for example to load multiple files sequentially:

         lfp2pgsql nn00.dxf contours | psql -d opendata
         lfp2pgsql -a nn01.dxf contours | psql -d opendata
         lfp2pgsql -a nn02.dxf contours | psql -d opendata
         ...

The -p flag limits the SQL statements to those necessary to create the table.
You could use this to script a loop to import a large quantity of data:

         lfp2pgsql -c nn00.dxf contours | psql -d opendata
         lfp2pgsql -a nn00.dxf contours | psql -d opendata
         lfp2pgsql -a nn01.dxf contours | psql -d opendata
         lfp2pgsql -a nn02.dxf contours | psql -d opendata
         ...

The -c flag is the default option, it ouputs SQL to create the table and 
then to insert the data from the DXF file.  The following are equivalent:

         lfp2pgsql -c nn00.dxf contours | psql -d opendata
         lfp2pgsql nn00.dxf contours | psql -d opendata

The -c, -p, -a, and -d flags are mutually exclusive, if you supply more than
one lfp2pgsql will exit with an error.

The -I flag causes lfp2pgsql to create an index on the geometry column of 
the resulting table.  You can use the -I flag with any of the other flags:

         lfp2pgsql -c -I  nn00.dxf contours | psql -d opendata
         lfp2pgsql -p -I  nn00.dxf contours | psql -d opendata
         lfp2pgsql -a -I  nn00.dxf contours | psql -d opendata
         lfp2pgsql -d -I  nn00.dxf contours | psql -d opendata

4) Landform Panorama Features

The following are the features that ae contained within the Landform Panorama
DXF files.  At this time lfp2pgsql only creates SQL INSERT statements for the
following subset of features:

         G8040201       Contours
         G8040202       Lakes
         G8040203       Breakline
         G0804204       Coastline
         G8040205       Ridgelines
         G8040207       Formlines

The following are the features that are ignored by lfp2pgsql:

         G8040200       Spothights [sic]
         G8040570       Copyrightsymbol
         G8040571       Footnotes
         G8040572       Gridlinesandvalues
         G8040573       Gridvalues
         G8040575       Default

I am happy to update the parser if anyone has a good reason why the data I 
currently ignore should be handled in some way.

Keith
<keith.sharp@gmail.com>
March 2011

[1] http://www.ordnancesurvey.co.uk/oswebsite/products/landformpanorama/
[2] http://www.ordnancesurvey.co.uk/oswebsite/opendata/
[3] http://postgis.refractions.net/docs/ch04.html#shp2pgsql_usage
[4] http://lists.openstreetmap.org/pipermail/talk-gb/2011-March/011101.html
[5] http://lists.openstreetmap.org/pipermail/talk-gb/2011-March/011184.html