3 Replies Latest reply: Oct 5, 2012 12:21 AM by Simon Greener RSS

    determination the Direction and Borders problem

      hi all

      I Have Problem in How to determination the Direction And the neighbor For polygon As in the picture.

      picture in (http://www.4shared.com/photo/CQhYa1LV/1_online.html?)

      I Want determination :

      From north : polygon with object Id=.....
      From south : streets with object Id=.....
      From east :streets with object Id=.....
      From west : polygon with object Id=.....

      I have Started and I Identified the Directions I get line of land with line 29 meters is the North
      and line with 25.4 is south ......

      Now how I can Determination the border of land ?
      manes :
      north ... land with number 2
      south ... street with 15 meters width

      Can eny one Help Or have Good idea ?
        • 1. Re: determination the Direction and Borders problem
          Ying Hu-Oracle
          Not sure that I fully understand your problem.
          Here are some functions (or operator) you may be able to use:

          1) sdo_geom.relate( geom1, 'touch', geom2, tolerance) (or operator sdo_touch()) to get neighbors
          2) for each neighbor, bnd := sdo_geom.sdo_intersection(geom1, geom2, tolerance) to get the common boundary
          3) compare sdo_geom.sdo_centroid(geom1, tolerance) and sdo_geom.sdo_centroid(bnd, tolerance) to decide the direction
          • 2. Re: determination the Direction and Borders problem
            Luc Van Linden

            In addition for the direction you can have a look at an older contribution :

            Re: Query based on direction

            • 3. Re: determination the Direction and Borders problem
              Simon Greener
              Some real data (ie the sdo_geometry of the polygon in the image) would be useful.

              The main issue here is not so much the writing of the bearings and distances against the line segments,
              but determining which segments should be so labelled.

              I have dealt with the basics of extracting and marking polygon segments in in articles like this http://www.spatialdbadvisor.com/oracle_spatial_tips_tricks/74/spatial-pipelining before.

              But this is roughly how I would go about removing those shared boundary segments so that I only had those segments that front a street:
              select T_Vector(va.vector_id, va.element_id, va.subelement_id, va.startCoord, va.endCoord).AsSdoGeometry(null) as geom,
                           codesys.Cogo.Bearing (va.startCoord.x,va.startCoord.y,va.endCoord.x,va.endCoord.y) * (180/codesys.Constants.PI) ) AS bearing,
                     ROUND(codesys.Cogo.Distance(va.startCoord.x,va.startCoord.y,va.endCoord.x,va.endCoord.y),2) AS distance
                from source_table a,
                     table(ST_Vectorize(a.geom)) va,
                     source_table b
               where a.<primary key> = <value>
                 and sdo_covers(c.geom,
                                T_Vector(va.vector_id, va.element_id, va.subelement_id, va.startCoord, va.endCoord).AsSdoGeometry(null)) = 'TRUE'
                 and c.<primary key> <> a.<primary key>;
              The COGO and GEOM package and the T_Vector object are available for download from my website.

              In short you:

              1. Take the base polygon;
              2. Break it into 2 vertex segments;
              3. Use each segment to find a polygon in the original table it lies on;
              4. Ensure that the found polygon is not the same as the source of the segments;
              5. Generate the bearing and distance.