[Gdal-dev] OGR to access s57 file

[Frank Warmerdam]

kiruba nantham wrote:
> Dear sir,
>          
>         i am trying to make one ENC file reader using c++ language. i 
> just want to know how to diffentiate objects are in the ENC file using 
> OGR library?  for example there are many wreaks in the ENC file how to 
> sepate them as a ship wreak, dangerous wreak etc.. which OGR funtions i 
> should use?  if it is possible please give some example program.

Kiruba,

My suggestion is that you review the S-57 documentation carefully to see
if there are attributes that allow you to meaningfully differentiate
different kinds of wrecks.  Once you know how it is indicated in the S-57
data model it shouldn't be too hard to get the information out of OGR.

When I dump the WRECKS layer in an S-57 dataset the features look like:

OGRFeature(WRECKS):2163
   RCID (Integer) = 2164
   PRIM (Integer) = 1
   GRUP (Integer) = 2
   OBJL (Integer) = 159
   RVER (Integer) = 1
   AGEN (Integer) = 540
   FIDN (Integer) = 2135161787
   FIDS (Integer) = 688
   LNAM (String) = 021C7F43FBBB02B0
   LNAM_REFS (StringList) = (null)
   FFPT_RIND (IntegerList) = (null)
   CATWRK (Integer) = 1
   CONRAD (Integer) = (null)
   CONVIS (Integer) = (null)
   EXPSOU (Integer) = (null)
   HEIGHT (Real) = (null)
   NOBJNM (String) = (null)
   OBJNAM (String) = (null)
   QUASOU (String) = 2
   SOUACC (Real) = (null)
   STATUS (String) = (null)
   TECSOU (String) = (null)
   VALSOU (Real) = (null)
   VERACC (Real) = (null)
   VERDAT (Integer) = (null)
   VERLEN (Real) = (null)
   WATLEV (Integer) = 3
   INFORM (String) = (null)
   NINFOM (String) = (null)
   NTXTDS (String) = (null)
   SCAMAX (Integer) = (null)
   SCAMIN (Integer) = (null)
   TXTDSC (String) = (null)
   RECDAT (String) = (null)
   RECIND (String) = (null)
   SORDAT (String) = (null)
   SORIND (String) = (null)
   POINT (61.1031909 -32.4450159)

Hmm, looking in the gdal/data/s57expectedinput.csv file I see that
the CATWRK field can have the following values:

71,1,non-dangerous wreck
71,2,dangerous wreck
71,3,distributed remains of wreck
71,4,wreck showing mast/masts
71,5,wreck showing any portion of hull or superstructure

So, I think what you need to do is fetch the CATWRK feature attribute
from WRECKS, and compare the value to the range above (1-5).   So
looking at the s57expectedinput.csv file will help you identify what
integer values for some fields correspond with what textual strings.
But generally speaking the best reference is the S-57 specification.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | President OSGeo, http://osgeo.org