[gdal-dev] S57 dataset boundary issue
s duclos
sylvain_duclos at yahoo.com
Thu Oct 11 08:19:35 PDT 2012
Nikhil,
>If I have a polygon how to find out edges of it programmatic do we have any function to get all the edges of polygon(area)
OGR is modelled on the OpenGIS simple features data model,
http://www.gdal.org/ogr/ogr_arch.html
In this model there is no notion of edge like in S-57
You did use the OGR internal representation using RETURN_LINKAGES=ON
But that is for debugging .. it's not part of OGR official interface as I can see.
But RETURN_LINKAGES=ON give you a fighting chance if you need to find edge
and also to will need to hack the source code of OGR as it limit the output to 80 char.
rgds,
Sylvain.
>________________________________
> From: Nikhil Sai Parupalli <nikhil.parupalli at iictechnologies.com>
>To: s duclos <sylvain_duclos at yahoo.com>
>Cc: "gdal-dev at lists.osgeo.org" <gdal-dev at lists.osgeo.org>
>Sent: Thursday, October 11, 2012 1:26:47 AM
>Subject: RE: [gdal-dev] S57 dataset boundary issue
>
>Hey Sylvain,
>
>Thanks for your inputs, we have successfully implemented the same in our project .
>I have one more question i.e
>If I have a polygon how to find out edges of it programmatic do we have any function to get all the edges of polygon(area)
>
>
>Thanks and Regards
>Nikhil Sai Parupalli
>
>
>
>Note: Do not print this email until and unless it is really required. Save paper , stay Green
>
>________________________________________
>From: Nikhil Sai Parupalli
>Sent: Wednesday, October 10, 2012 9:07 PM
>To: s duclos
>Subject: RE: [gdal-dev] S57 dataset boundary issue
>
>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 8:43 PM
>To: Nikhil Sai Parupalli; Frank Warmerdam
>Cc: gdal-dev at lists.osgeo.org
>Subject: Re: [gdal-dev] S57 dataset boundary issue
>
>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
>>>>>
>>>>>
>>>>
>>>
>>
>
>
>
More information about the gdal-dev
mailing list