[gdal-dev] Topological pointer

[Frank Warmerdam]

On 12-10-07 10:02 PM, Nikhil Sai Parupalli wrote:
> Frank,
>
> As said I have my system variable as
>
> "RETURN_PRIMITIVES=ON,RETURN_LINKAGES=ON,LNAM_REFS=ON,
> UPDATES=APPLY,SPLIT_MULTIPOINT=ON,ADD_SOUNDG_DEPTH=ON"
>
> but still I couldn't  see TOPI field retrieved in my dataset..
> Will you elaborate and let me know.

Nikhil,

I don't know why you don't see it.  I see it fine on the "Edge"
layer which contains the linestring vector objects.

eg.

  OGRFeature(Edge):18
   RCNM (Integer) = 130
   RCID (Integer) = 19
   RVER (Integer) = 1
   RUIN (Integer) = 1
   NAME_RCNM_0 (Integer) = 120
   NAME_RCID_0 (Integer) = 21
   ORNT_0 (Integer) = 255
   USAG_0 (Integer) = 255
   TOPI_0 (Integer) = 1
   MASK_0 (Integer) = 255
   NAME_RCNM_1 (Integer) = 120
   NAME_RCID_1 (Integer) = 20
   ORNT_1 (Integer) = 255
   USAG_1 (Integer) = 255
   TOPI_1 (Integer) = 2
   MASK_1 (Integer) = 255
   LINESTRING (60.775 -32.6249972)

> I have one more question:
> How do we find  area outer boundaries are encoded clockwise based
> on Orientation or USAG.
> here when I retrieve S57 dataset I get multiple ORNT values for a single object.

I am not aware of any definition of outer ring winding direction.
I think the ORNT field values you see on polygons are indicating
which direction the edges were used in when composing the ring(s)
of the polygon.


   NAME_RCNM (IntegerList) = (7:130,130,130,130,130,130,130)
   NAME_RCID (IntegerList) = (7:691,391,690,52,1336,1503,1512)
   ORNT (IntegerList) = (7:2,2,2,2,1,1,1)
   USAG (IntegerList) = (7:1,1,1,1,1,1,1)
   MASK (IntegerList) = (7:255,255,255,255,255,255,255)

So in the above feature, RCID 691 is used with orientation "2",
usage "1" and mask "255".

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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