[MAPSERVER-USERS] Problems calculating MAXSCALES

[Tamas Szekeres]

You'll have to create an OSGEO user ID and login before editing the ticket:

https://www.osgeo.org/cgi-bin/ldap_create_user.py

Best regards,

Tamas



2008/8/13 Rob <gis at vanbooth.com>:
> Sorry - didnt reply to whole list
>
>
> ---------- Forwarded message ----------
> From: Rob <gis at vanbooth.com>
> Date: 2008/8/13
> Subject: Re: [MAPSERVER-USERS] Problems calculating MAXSCALES
> To: Tamas Szekeres <szekerest at gmail.com>
>
>
> I was unable to reopen the ticket with comments - "TICKET_APPEND
> privileges are required to perform this operation"
>
> If someone else could reopen on my behalf, this is what I wrote for
> the comments -
>
> I've recently updated from 4.8.6 to 5.0.2 and fallen foul of this
> defect, where layers are not visible when I would expect them to be.
>
> I'm in OSGB Projection (epsg:27700) but I didn't include this
> information in my sample mapfiles, in case it was a projection related
> issue.  My implementation uses mapscript rather than the cgi mapserv
> process, but I have been testing using shp2img.
>
> 4.8.3 Mapfile
>
> {{{
> MAP
>  EXTENT 200000 200000 266145 266145
>  IMAGECOLOR 255 255 255
>  IMAGETYPE png
>  RESOLUTION 96.000000
>  SIZE 500 500
>  STATUS ON
>  TRANSPARENT TRUE
>  UNITS METERS
>  NAME "Base"
>  IMAGEQUALITY 75
>
>  LEGEND
>   IMAGECOLOR 255 255 255
>   KEYSIZE 20 10
>   KEYSPACING 5 5
>   LABEL
>     SIZE MEDIUM
>     TYPE BITMAP
>     BUFFER 0
>     COLOR 0 0 0
>     FORCE FALSE
>     MINDISTANCE -1
>     MINFEATURESIZE -1
>     OFFSET 0 0
>     PARTIALS TRUE
>   END
>   POSITION LL
>   STATUS OFF
>  END
>  WEB
>   IMAGEPATH "c:\tmp\"
>   IMAGEURL "/"
>   QUERYFORMAT text/html
>   LEGENDFORMAT text/html
>   BROWSEFORMAT text/html
>  END
>  LAYER
>   MAXSCALE 500000
>   MINSCALE 0
>   NAME "Land"
>   STATUS ON
>   TRANSPARENCY 100
>   TYPE RASTER
>   UNITS METERS
>   DATA "C:\Documents and Settings\Administrator\Desktop\gb\gbpng.tif"
>  END
> END
> }}}
>
>
> 5.0.2 Mapfile
>
> {{{
> MAP
>  EXTENT 200000 200000 266145 266145
>  IMAGECOLOR 255 255 255
>  IMAGETYPE png
>  RESOLUTION 96.000000
>  SIZE 500 500
>  STATUS ON
>  TRANSPARENT TRUE
>  UNITS METERS
>  NAME "Base"
>  OUTPUTFORMAT
>   NAME "png"
>   MIMETYPE "image/png"
>   DRIVER "GD/PNG"
>   EXTENSION "png"
>   IMAGEMODE "PC256"
>   TRANSPARENT TRUE
>  END
>  PROJECTION
>   "init=epsg:27700"
>  END
>  LEGEND
>   IMAGECOLOR 255 255 255
>   KEYSIZE 20 10
>   KEYSPACING 5 5
>   LABEL
>     SIZE MEDIUM
>     TYPE BITMAP
>     BUFFER 0
>     COLOR 0 0 0
>     FORCE FALSE
>     MINDISTANCE -1
>     MINFEATURESIZE -1
>     OFFSET 0 0
>     PARTIALS TRUE
>   END
>   POSITION LL
>   STATUS OFF
>  END
>  WEB
>   IMAGEPATH "c:\tmp\"
>   IMAGEURL "/"
>   QUERYFORMAT text/html
>   LEGENDFORMAT text/html
>   BROWSEFORMAT text/html
>  END
>  LAYER
>   DEBUG 5
>   MAXSCALEDENOM 500000
>   MINSCALEDENOM 0
>   NAME "Land"
>   STATUS ON
>   TRANSPARENCY 100
>   TYPE RASTER
>   UNITS METERS
>   DATA "C:\Documents and Settings\Administrator\Desktop\gb\gbpng.tif"
>  END
> END
> }}}
>
> GBPNG.TFW
>
> {{{
> 333.333333333
> 0.000
> 0.000
> -333.333333333
> 166.66666666
> 649833.33333333
> }}}
>
> Any 1000x1000 image should work.
>
> Running shp2img against 4.8.3 will produce a valid image.  Running
> shp2img against 5.0.2 does not.
>
> Code is currently
>
>
> {{{
> center_y = (extent.miny+extent.maxy)/2.0;
>  md = (width-1)/(resolution*msInchesPerUnit(units, center_y)); /*
> remember, we use a pixel-center to pixel-center extent, hence the
> width-1 */
>  gd = extent.maxx - extent.minx;
>  *scale = gd/md;
> }}}
>
> For the extents in the mapfiles, this gives a scale of 500997
>
> Previously, using (width) instead of (width-1), we would have had 499993
>
> My desktop GIS product seems to agree with the calculation to result
> in 499993, judging by the bbox it requests when zooming to 1:500,000
>
> Full mapserver-users conversation is here -
> http://www.nabble.com/Problems-calculating-MAXSCALES-td18926188.html
> _______________________________________________
> mapserver-users mailing list
> mapserver-users at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/mapserver-users
>