ok - got zoom to work - another question

[Joseph Norris]

Thanks Eric - so as I understand you:

MAP
  NAME CalMap
  STATUS ON
  EXTENT 5890870.385 -192053.200 8943310.847 3226086.749
  IMAGETYPE GIF
  SIZE 600 600
  SHAPEPATH
"/usr/local/apache/htdocs/mco.communityservers.com/htdocs/maps/teacher/tdata
"
  IMAGECOLOR 255 255 255
  TEMPLATEPATTERN "map"

  SYMBOL
    NAME 'circle'
    TYPE ELLIPSE
    POINTS 1 1 END
    FILLED TRUE
  END


  LAYER
    NAME "cal_zp_st"
    TYPE POLYGON
    DATA "cal_zp_st"
    STATUS DEFAULT
    CLASSITEM "ZCTA"

    CLASS
        EXPRESSION
/94087|90408|94107|95118|94530|74580|95404|93711|94904|92030|94121|91042|961
01|94523|95548|95658|92057|92503/
      STYLE
        SYMBOL 'circle'
        SIZE 2
        COLOR 255 102 102
      END

    END

    CLASS
      EXPRESSION /./
      OUTLINECOLOR 204 204 204
    END
  END
  LAYER
    NAME "poly_minscale"
    TYPE POLYGON
    DATA "cal_zp_st"
    STATUS DEFAULT
    MINSCALE ????
    CLASS
     SYMBOL 'circle'
      SIZE 2
      COLOR 255 102 102
     END
  END
     LAYER
    NAME "poly_maxscale"
    TYPE POLYGON
    DATA "cal_zp_st"
    STATUS DEFAULT
    MAXSCALE????
 I don't know what the class would be if any
  END


END # end map from header

How do I determine the minscale and maxscale?

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);

-----Original Message-----
From: UMN MapServer Users List [mailto:MAPSERVER-USERS at lists.umn.edu]On
Behalf Of Eric Bridger
Sent: Monday, November 22, 2004 9:53 AM
To: MAPSERVER-USERS at lists.umn.edu
Subject: Re: [UMN_MAPSERVER-USERS] ok - got zoom to work - another question

At 08:39 AM 11/22/2004 -0800, Joseph Norris wrote:
>Everyone,
>
>I have my zoom working but now I would like to tackle something else.  I am
>putting an ellipse in the zip polygons if there is a 1-more teachers there.
>For each zip there maybe a max of 10 teachers.  I would like an ellipse or
>symbol for each one so that when the user zooms into the polygon they can
>see a symbol for each teacher. Can I do this within the class?  If so how
or
>would be the best way to handle this?


You can do this in the map file by creating two layers and using MAXSCALE,
MINSCALE.
Layer 1 has one ellipse per zip wherever there are 1-10 teachers.
MINSCALE is set so that it won't appear when you are zoomed in.
Layer 2 has one ellipse for each teacher and has MAXSCALE set so that it
turns on when Layer 1 is turned off.

Of course if you are using Perl Mapscript you will need to calculate the
scale yourself and turn on and off the layers yourself.
Here's and example:

my $current_scale = calculateScale($map, $imgext[0], $imgext[2]);
# From mapserver3.6.4: mapscale.c msCalculateScale().  This is not a
precision thing. We don't worry about
# msAdjustExtent() since in all our maps, image SIZE has same aspect ratio
as the map EXTENT.
# $minx and $maxx are optional in which case the current extent of the map
is used.

# Be careful about the current map's extent. zoomMap() changes the extents.

sub calculateScale{
    my ($map, $minx, $maxx) = @_;
    if(!$minx){
        $minx = $map->{extent}->{minx};
        $maxx = $map->{extent}->{maxx};
    }
    my @inchesPerUnit = (1, 12, 63360.0, 39.3701, 39370.1, 4374754);
    my $width = $map->{width};
    my $units = $map->{units}; # index into unitsPerUnit array
    my $resolution = $map->{resolution};
    my $md = $width / ($resolution * $inchesPerUnit[$units]);
    my $gd = $maxx - $minx;
    return($gd/$md);
}

Eric