OASIS Emergency Management TC

Carl and others-
Question:
The Polygon element in targetArea is a list of lat lon pairs that represents a polygon.  However, one problem that I have noted when storing polygons in a geospatial database, or exposing to GIS tools is RingOrientation.  Notably, you normally follow the “left-hand” rule, which states that if you are walking the polygon you left hand should be pointing towards the center of the polygon area, which results in a counter-clockwise representation of points in the polygon.  If this is the case, I think our example in the DE documentation was constructed using the opposite linear ring orientation.  When validating a polygon, do we assume a certain ring orientation, or state that it can be either or, and just take the case that doesn’t span multiple hemispheres?
Don McGarry
The MITRE Corp.
Office: 315-838-2669
Cell: 315-383-1197
dmcgarry@mitre.org

Rather then "invent" a specific approach for targetArea, why not follow ISO 
19107 as the abstract model and GML as the "implementation" instance? Polygon is 
defined in the OASIS "where" draft and in the requirements document (which is 
available in the Kavi document archive). Very clearly stated. We should be 
consistent with how ISO, OMA, IETF, OGC, and others are defining polygon.
 
Cheers

Carl
 

  


                                                

					
                                                    

        
                                                
				
                                                

                                                    
                                                        
                                                        Original Message
                                                
                                                 Original Message ----- 
  
From: 
  dmcgarry@mitre.org">McGarry, Donald 
  P. 
  
To: emergency@lists.oasis-open.org 
  
  
Cc: creed@opengeospatial.org)">Carl Reed 
  (creed@opengeospatial.org) 
  
Sent: Monday, May 03, 2010 9:41 AM
  
Subject: Polygon in TargetAreaType
  


  

  
Carl and others-
  
Question:
  
The Polygon element in targetArea is a list of lat lon 
  pairs that represents a polygon.  However, one problem that I have noted 
  when storing polygons in a geospatial database, or exposing to GIS tools is 
  RingOrientation.  Notably, you normally follow the “left-hand” rule, 
  which states that if you are walking the polygon you left hand should be 
  pointing towards the center of the polygon area, which results in a 
  counter-clockwise representation of points in the polygon.  If this is 
  the case, I think our example in the DE documentation was constructed using 
  the opposite linear ring orientation.  When validating a polygon, do we 
  assume a certain ring orientation, or state that it can be either or, and just 
  take the case that doesn’t span multiple hemispheres?
  

  
Don McGarry
  
The MITRE Corp.
  
Office: 315-838-2669
  
Cell: 315-383-1197
  
dmcgarry@mitre.org
  

Carl-
What does ISO 19107 state for Exterior Ring Orientation for a polygon?  I haven’t had any problem accomplishing this in Where, because as you stated, it’s very clear how the points have to be arranged.  The problem here is that targetarea in the DE is just a string of points and I wasn’t sure if we need to specify ring orientation in the conformance document.
-Don
Office: 315-838-2669
Cell: 703-595-9375 NEW
dmcgarry@mitre.org
From: Carl Reed [mailto:creed@opengeospatial.org]
Sent: Wednesday, May 05, 2010 10:01 AM
To: McGarry, Donald P.; emergency@lists.oasis-open.org
Subject: Re: Polygon in TargetAreaType
Rather then "invent" a specific approach for targetArea, why not follow ISO 19107 as the abstract model and GML as the "implementation" instance? Polygon is defined in the OASIS "where" draft and in the requirements document (which is available in the Kavi document archive). Very clearly stated. We should be consistent with how ISO, OMA, IETF, OGC, and others are defining polygon.
 
Cheers

Carl
 


                                                

					
                                                    

        
                                                
				
                                                

                                                    
                                                        
                                                        Original Message
                                                
                                                 Original Message ----- 
From: McGarry, Donald P. 
To: emergency@lists.oasis-open.org 
Cc: Carl Reed (creed@opengeospatial.org) 
Sent: Monday, May 03, 2010 9:41 AM
Subject: Polygon in TargetAreaType
Carl and others-
Question:
The Polygon element in targetArea is a list of lat lon pairs that represents a polygon.  However, one problem that I have noted when storing polygons in a geospatial database, or exposing to GIS tools is RingOrientation.  Notably, you normally follow the “left-hand” rule, which states that if you are walking the polygon you left hand should be pointing towards the center of the polygon area, which results in a counter-clockwise representation of points in the polygon.  If this is the case, I think our example in the DE documentation was constructed using the opposite linear ring orientation.  When validating a polygon, do we assume a certain ring orientation, or state that it can be either or, and just take the case that doesn’t span multiple hemispheres?
Don McGarry
The MITRE Corp.
Office: 315-838-2669
Cell: 315-383-1197
dmcgarry@mitre.org