[gdal-dev] S57 dataset boundary issue
s duclos
sylvain_duclos at yahoo.com
Wed Oct 10 08:13:37 PDT 2012
Hi Nikhil,
> Based on the code which you have sent we could find out CW and CCW, but not
> outer/inner
The outer ring of OGRGeometryH poly is the ring 0 (zero).
In C code the OGR call:
guint nRingCount = OGR_G_GetGeometryCount(hGeom);
will give you the number of rings in a poly.
Say there is 2 rings for this hGeom. Then the outer ring is
OGRGeometryH *hGeomRef_outter = OGR_G_GetGeometryRef(hGeom, 0);
and the inner ring is
OGRGeometryH *hGeomRef_inner = OGR_G_GetGeometryRef(hGeom, 1);
> Please have a look at that data set once and let me know.
There is nothing in attachment
rgds,
Sylvain.
----- Original Message -----
> From: Nikhil Sai Parupalli <nikhil.parupalli at iictechnologies.com>
> To: s duclos <sylvain_duclos at yahoo.com>; Frank Warmerdam <warmerdam at pobox.com>
> Cc: "gdal-dev at lists.osgeo.org" <gdal-dev at lists.osgeo.org>
> Sent: Wednesday, October 10, 2012 10:40:27 AM
> Subject: RE: [gdal-dev] S57 dataset boundary issue
>
> Hey Sylvain,
>
> Thanks for trying the data which I have sent.
>
> Could you be helping me how this works like outer boundary and inner boundary.
>
>
>
> Based on the code which you have sent we could find out CW and CCW, but not
> outer/inner
> Please have a look at that data set once and let me know.
> Or if you have any sample data with simple representation of outer and inner
> boundaries please do share with me.
>
>
>
>
> Thanks and Regards
> Nikhil Sai Parupalli
>
>
>
> Note: Do not print this email until and unless it is really required. Save paper
> , stay Green
>
> ________________________________________
> From: s duclos [sylvain_duclos at yahoo.com]
> Sent: Wednesday, October 10, 2012 7:59 PM
> To: Nikhil Sai Parupalli; Frank Warmerdam
> Cc: gdal-dev at lists.osgeo.org
> Subject: Re: [gdal-dev] S57 dataset boundary issue
>
> Hi Nikhil,
>
> I loaded US1GC09M//US1GC09M.000 .. it's huge :)
>
> It's the Gulf of Mexico .. now where should I look ?
>
>
>
> About the inner / outer ring. As I said before, I just assume that OGR
> send me the outer ring first. And, up to now, my code is working fine.
>
>
> rgds,
>
> Sylvain.
>
>
>
>
> ----- Original Message -----
>> From: Nikhil Sai Parupalli <nikhil.parupalli at iictechnologies.com>
>> To: s duclos <sylvain_duclos at yahoo.com>; Frank Warmerdam
> <warmerdam at pobox.com>
>> Cc: "gdal-dev at lists.osgeo.org" <gdal-dev at lists.osgeo.org>
>> Sent: Wednesday, October 10, 2012 9:40:54 AM
>> Subject: RE: [gdal-dev] S57 dataset boundary issue
>>
>> Could you try on this data set please
>>
>> Thanks and Regards
>> Nikhil Sai Parupalli
>>
>>
>>
>> Note: Do not print this email until and unless it is really required. Save
> paper
>> , stay Green
>>
>> ________________________________________
>> From: s duclos [sylvain_duclos at yahoo.com]
>> Sent: Wednesday, October 10, 2012 7:02 PM
>> To: Nikhil Sai Parupalli; Frank Warmerdam
>> Cc: gdal-dev at lists.osgeo.org
>> Subject: Re: [gdal-dev] S57 dataset boundary issue
>>
>> Nikhil,
>>
>> I loaded your ENC.
>>
>> I see a number of depth area (DEPARE) and anchor zone area (ACHARE).
>>
>> But no inner ring!
>>
>> Is there an inner rings somewhere I should see?
>>
>>
>>
>> rgds,
>>
>> Sylvain.
>>
>>
>>
>> ----- Original Message -----
>>> From: Nikhil Sai Parupalli
> <nikhil.parupalli at iictechnologies.com>
>>> To: s duclos <sylvain_duclos at yahoo.com>; Frank Warmerdam
>> <warmerdam at pobox.com>
>>> Cc: "gdal-dev at lists.osgeo.org"
> <gdal-dev at lists.osgeo.org>
>>> Sent: Wednesday, October 10, 2012 8:00:41 AM
>>> Subject: RE: [gdal-dev] S57 dataset boundary issue
>>>
>>> Duclos,
>>>
>>> Please see this sample data attached.
>>> So as per the code given by you we have tried and got result i.e able
> to
>> find
>>> out area
>>>
>>> some times it shows area<0 and some times area>0 hence we get
> CW and
>> CCW.
>>> But how do we classify in layer which is outer boundary and which is
> inner
>>> boundary
>>>
>>>
>>>
>>>
>>> Geometry testgeo = geomLAKARE.GetBoundary();
>>> double area = 0;
>>> for (int l = 0; l <
>>> testgeo.GetPointCount() - 1; l++)
>>> {
>>> double x1 = testgeo.GetX(l);
>>> double y1 = testgeo.GetY(l);
>>> double x2 = testgeo.GetX(l +
> 1);
>>> double y2 = testgeo.GetY(l +
> 1);
>>> area += (x1 * y2) - (x2 * y1);
>>> }
>>>
>>> Thanks and Regards
>>> Nikhil Sai Parupalli
>>>
>>>
>>>
>>> Note: Do not print this email until and unless it is really required.
> Save
>> paper
>>> , stay Green
>>>
>>> ________________________________________
>>> From: s duclos [sylvain_duclos at yahoo.com]
>>> Sent: Tuesday, October 09, 2012 11:58 PM
>>> To: Frank Warmerdam; Nikhil Sai Parupalli
>>> Cc: gdal-dev at lists.osgeo.org
>>> Subject: Re: [gdal-dev] S57 dataset boundary issue
>>>
>>> Frank & Nikhil,
>>>
>>>
>>> Frank asked:
>>>
>>>> are, I'm not sure what I or others can do about
>>>> the performance cost of checking.
>>>
>>>
>>> If I understand the problem, then it cost nothing!
>>>
>>> You have to check the winding while loading a OGRGeometryH
>>> like so:
>>> double area = 0;
>>> for (unsigned int i=0; i<vert_count-1; i++) {
>>> double x1 = OGR_G_GetX(hRing, i);
>>> double y1 = OGR_G_GetY(hRing, i);
>>> double x2 = OGR_G_GetX(hRing, i+1);
>>> double y2 = OGR_G_GetY(hRing, i+1);
>>> area += (x1*y2) - (x2*y1);
>>> }
>>>
>>>
>>> If the area < 0 then it is CW (clockwise) and > 0 is CCW
> (Counter
>> CW).
>>>
>>> Note that in S57 the exterior ring must be CW and
>>> interior ring are CCW.
>>>
>>> But in S57 there is no order between rings. So interior ring
>>> might come first. I think WKT fix this. In my code I assume
>>> that OGR place the exterior ring first.
>>>
>>>
>>> We have been trough this before. At the time the question
>>>
>>> was if S57 allow for many exterior ring for the same poly.
>>>
>>> I guess it all depend on HO and how they encode the data.
>>>
>>> I'm using mostly Canadian ENC and found no problem.
>>>
>>> But other HO might encode ENC differently ..
>>>
>>>
>>>
>>>
>>> rdgs,
>>>
>>>
>>> Sylvain Duclos.
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>> ________________________________
>>>> From: Frank Warmerdam <warmerdam at pobox.com>
>>>> To: Nikhil Sai Parupalli
> <nikhil.parupalli at iictechnologies.com>
>>>> Cc: "gdal-dev at lists.osgeo.org"
>> <gdal-dev at lists.osgeo.org>
>>>> Sent: Tuesday, October 9, 2012 12:25:29 PM
>>>> Subject: Re: [gdal-dev] S57 dataset boundary issue
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> On Mon, Oct 8, 2012 at 10:28 PM, Nikhil Sai Parupalli
>>> <nikhil.parupalli at iictechnologies.com> wrote:
>>>>
>>>> HI All,
>>>>> ,
>>>>>
>>>>> Thanks for the reply in below data
>>>>>
>>>>> 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)
>>>>>
>>>>> RCID 691 ORNT has 2 and USAG is 1 based on this data we
> could
>> identify
>>> that RCID 691 is of exterior boundary with reverse direction.
>>>>>
>>>>> So if I have 1000 RCID in NAME_RCID which is vise versa for
> the
>> above
>>> condition I need to display that RCIDS list as errors.
>>>>> So it makes 1000 conditional checks hence reducing
> performance.
>>>>>
>>>>> Please let us know further.
>>>>
>>>>
>>>> Nikhil,
>>>>
>>>>
>>>> I'm afraid I don't follow your point. Are you trying to
>>>> do some sort of ring orientation validation and identify
>>>> ones that don't match your expectations? And you
>>>> are concerned about the performance cost?
>>>>
>>>>
>>>> I don't know why you are doing this, and if you
>>>> are, I'm not sure what I or others can do about
>>>> the performance cost of checking.
>>>>
>>>>
>>>> Best regards,--
>>>>
>>
> ---------------------------------------+--------------------------------------
>>>> 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 | Geospatial Software
> Developer
>>>>
>>>>
>>>> _______________________________________________
>>>> gdal-dev mailing list
>>>> gdal-dev at lists.osgeo.org
>>>> http://lists.osgeo.org/mailman/listinfo/gdal-dev
>>>>
>>>>
>>>
>>
>
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