[ gpsdrive ] making use of AIS data

[Hamish]

Doug wrote:
> AIS targets (a hack of the friends tracker code perhaps),

Guenther:
>> are these targets static or moving ones?

they are moving targets highly similar to friendsd blips.
It is real-time position and speed+direction data for ships,
which are typically traveling much faster than you are (so
static representation is dangerous).

if integrated into a NMEA stream with a multiplexer, we need to
start parsing NMEA again. an alternative is to patch/add AIS
support into GPSD (a reoccurring request on their ML AFAICT).


>> [...], I see two possibilites:
>> - using a kind of friends server to provide the data

yes please (or integrate it into/reuse friendsd display code)

>> - having an external program, that gets those data from
>>   somehwere, and inserts it into the gpsdrive database
>>   temporarily

mmmph, vulnerable to left-over cruft in the DB, etc., and relies
on our timeout loop too much.  no thanks


Doug:
> and ENC charts which are free as in beer.

Guenther:
>> are they available via wms?

yes-

Chris h:
>>> http://ocs-spatial.ncd.noaa.gov/wmsconnector/com.esri.wms.Esrimap/encdirect?
Service=WMS&Version=1.1.1&Request=GetCapabilities

but noaa's WMS renders them as rather ugly raster bitmaps and
raster navigation charts (RNCs) + gdal_slice.sh is currently the
best option here.

Chris:
>>> Now if gdal support for wms is working up to snuff, we may
>>> have a very cool solution.

We don't need GDAL support for WMS. You can give enough data 
directly in the WMS request URL to form a nice gpsdrive backdrop
tile. This is exactly what we do for the NASA LANDSAT downloads
in Options->Maps->Downloads.

FWIW for the WMS raster driver in GDAL 1.5 and newer you create
a small ~10 line XML file with the request details and it works
from that.


For ENC support in GpsDrive it is still my hope that libS52
could be used to render the data, in a similar way as Mapnik
is rendering OSM data now.

see http://apps.sourceforge.net/mediawiki/gpsdrive/index.php?title=Marine_Howto
  (please help improve the wiki page!)

http://grass.osgeo.org/wiki/BSB_data
http://grass.osgeo.org/wiki/S-57_data#libS52
http://openev.cvs.sourceforge.net/openev/contrib/S52/


In the short term, download of rasterized backdrop tiles from
NOAA's WMS could be easily added as a copy of gpsfetchmap.pl's
landsat_url() subroutine with different base URL and layer
names. (or in map_download.c, but I'd prefer to see a prototype
running in gpsfetchmap.pl first.

the very tricky bit is choosing which layers to include. the S-52
gives recommendations of which features to display based on map
scale class, I'd say reuse those. But you would have to enter
that data by hand. If someone provides a list of layernames
per scale band, I might do the rest.


Hamish