Fwd: [MAPSERVER-USERS] Problems calculating MAXSCALES

[Stephen Woodbridge]

Rob,

Please post the new ticket number so we can follow this issue.

Thanks,
   -Steve W

Daniel Morissette wrote:
> Glad to hear that Trac prevents reopening closed tickets by default. 
> This is not a bad thing since that ticket was closed in a previous 
> release and reopening tickets usually leads to confusion.
> 
> I'd suggest you open a new ticket and refer to the original one that you 
> were trying to reopen.
> 
> Daniel
> 
> 
> Rob wrote:
>> 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
> 
>