[Mapserver-users] Non-Rectangular Tiles in TILEINDEX ?

Thu May 1 12:48:54 PDT 2003

Yes, although I need to look at the code to be sure. Even with though
there are situations where
a tile may be processed when it doesn't intersect the AOI it's still
far better than no tiling in all. In
general regular shaped tiles will provide the best performance as Ed
mentions.

Steve

>>> "Ed McNierney" <ed at topozone.com> 05/01/03 01:59PM >>>
Steve -

Thanks; I didn't realize that.  So non-rectangular tiles basically end
up being treated the same as rectangular tiles (i.e. bounding boxes)
enclosing the same polygons?

	- Ed

Ed McNierney
President and Chief Mapmaker
TopoZone.com / Maps a la carte, Inc.
73 Princeton Street, Suite 305
North Chelmsford, MA  01863
ed at topozone.com 
(978) 251-4242 

-----Original Message-----
From: Steve Lime [mailto:steve.lime at dnr.state.mn.us] 
Sent: Thursday, May 01, 2003 1:56 PM
To: BBruce at gov.mb.ca; mapserver-users at lists.gis.umn.edu; Ed McNierney
Subject: RE: [Mapserver-users] Non-Rectangular Tiles in TILEINDEX ?

Actually there is no pre-requisite for tiles other than that they be
polygons. Behind the
scenes the decision to process a tile or not is based on the bounding
box of that feature
(I believe) so there are certain inefficiencies that can occur with
irregularly shaped tiles
that don't truly intersect the area of interest. I and others have use
things like counties
or landsat footprints with success in the past.

Steve

Stephen Lime
Data & Applications Manager

Minnesota DNR
500 Lafayette Road
St. Paul, MN 55155
651-297-2937

>>> "Ed McNierney" <ed at topozone.com> 04/30/03 07:26PM >>>
Bob -

Your TILEINDEX should be rectangles.  The intent of a TILEINDEX is to
allow MapServer to quickly determine whether to examine an input file
to
see if it has any visible features on the current map request.
Rectangular tiles can be very quickly examined to see if they
intersect
the map viewframe.  If so, the source is opened and any files that
REALLY intersect the view are drawn.

Supporting non-rectangular tiles would be more complex and somewhat
slower, and would probably be of rather little benefit in most
applications.  A good combination of rectangular tile indexes and
spatial indexing will produce very good performance.

            - Ed

Ed McNierney

President and Chief Mapmaker

TopoZone.com / Maps a la carte, Inc.

73 Princeton Street, Suite 305

North Chelmsford, MA  01863

Phone: (978) 251-4242  Fax: (978) 251-1396

ed at topozone.com 

-----Original Message-----
From: Bruce, Bob (CON) [mailto:BBruce at gov.mb.ca] 
Sent: Wednesday, April 30, 2003 7:54 PM
To: 'Mapserver Mailing List'
Subject: [Mapserver-users] Non-Rectangular Tiles in TILEINDEX ?

I have been experimenting with TILEINDEXs in order to evaluate their
functionality for my applications.

I have successfully displayed a TILEINDEX of 20 orthophotos in my
browser.

Next I wanted to try displaying a set of project mapping areas and
built
an index map of polygons of these areas. I included this index map as
a
TILEINDEX in my map file and do not get anything displayed, instead I
get a blank display. This leads me to wonder if this is because my
tile
polygons are non-rectangular. Does the Map Server require tiles to be
rectangular or can it work with irregularly shaped tiles? I have
successfully displayed my dataset that I'm using as a TILEINDEX as a
line file, so I know that the server will work with this file.

For your reference, I have included the definition of this layer:

LAYER # DLS Polys
  NAME "DLSPolys"
  TILEINDEX "TilesWWinnipeg_CARIS/TilesWWinnipeg"
  TILEITEM "MAPKEY"
  STATUS DEFAULT
  TYPE POLYGON
  CLASSITEM "MAPKEY"
  CLASS # Whole DLS Parcel
    STATUS ON
    NAME "WHOLE DLSPOLY"
    COLOR 255 202 149
    OUTLINECOLOR 0 0 0
  END # end of Whole DLS Parcel class object
END # end of layer object

thanks,

            Bob Bruce

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