Just trying to get a better understanding.

[Jacob Delfos]

Joseph,

A shapefile can hold any (and only one) of three types of object: point, line or polygon. The shape objects are stored in a sequential order of some sort (normally the order in which they have been created), and the DBF file holds the attribute in the same order. So the link between the spatial object and the attribute is simply sequential. I don't think it makes use of bounding rectangles (except if you create a spatial index, correct me if I'm wrong).

If you are able to open up the DBF file in Excel, you will see it's just a table. The .shp and .shx file hold the spatial component for each row.

Hope this is what you meant.

Jacob


-----Original Message-----
From: UMN MapServer Users List [mailto:MAPSERVER-USERS at LISTS.UMN.EDU] On Behalf Of Joseph Norris
Sent: 8 December 2004 07:03
To: MAPSERVER-USERS at LISTS.UMN.EDU
Subject: [UMN_MAPSERVER-USERS] Just trying to get a better understanding.


I have this simple shapefile:

File Bounds: ( 6471392.899,  282843.628,0,0)
         to  ( 8433025.828, 2304680.124,0,0)

Shape:0 (Point)  nVertices=1, nParts=0
  Bounds:( 7750718.722, 1391592.674, 0, 0)
      to ( 7750718.722, 1391592.674, 0, 0)
     ( 7750718.722, 1391592.674, 0, 0)

Shape:1 (Point)  nVertices=1, nParts=0
  Bounds:( 6471392.899, 2304680.124, 0, 0)
      to ( 6471392.899, 2304680.124, 0, 0)
     ( 6471392.899, 2304680.124, 0, 0)

Shape:2 (Point)  nVertices=1, nParts=0
  Bounds:( 8433025.828,  282843.628, 0, 0)
      to ( 8433025.828,  282843.628, 0, 0)
     ( 8433025.828,  282843.628, 0, 0)

Shape:3 (Point)  nVertices=1, nParts=0
  Bounds:( 6862716.092, 1226032.862, 0, 0)
      to ( 6862716.092, 1226032.862, 0, 0)
     ( 6862716.092, 1226032.862, 0, 0)

Shape:4 (Point)  nVertices=1, nParts=0
  Bounds:( 7249022.321, 1677559.623, 0, 0)
      to ( 7249022.321, 1677559.623, 0, 0)
     ( 7249022.321, 1677559.623, 0, 0)

And it relates to this dbf file:

7750718.72:1391592.67:Fred Flinstone
6471392.9:2304680.12:Jeff Jackson
8433025.83:282843.63:Trueman Polygonas
6862716.09:1226032.86:Alfred Espinoza
7249022.32:1677559.62:Jim Apple

I can bring this layer into place over my main map file and I see the
points. What I do not see is the relationship between the xy coordinates in
the dbf file and the Bounds in the shape file.

Can someone give me an understanding of this?

Thanks.


#Joseph Norris (Perl - what else is there?/Linux/CGI/Mysql) print @c=map chr
$_+100,(6,17,15,16,-68,-3,10,11,16,4,1,14,-68,12,1,14,8,-68,4,-3,-1,7,1,14,-
68,-26,11,15,1,12,4,-68,-22,11,14,14,5,15,-90);
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