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<DIV><SPAN class=029411807-22062006><FONT face=Arial color=#0000ff
size=2>Hi,</FONT></SPAN></DIV>
<DIV><SPAN class=029411807-22062006><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=029411807-22062006><FONT face=Arial color=#0000ff size=2>If
you now the dotpitch (distance between two pixels) of your screen, you
can accurately calculate the resolution and make the scale ratio
correct.</FONT></SPAN></DIV>
<DIV><SPAN class=029411807-22062006><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=029411807-22062006><FONT face=Arial color=#0000ff size=2>If
dotpitch is 0.25 mm/pixel then:</FONT></SPAN></DIV>
<DIV><SPAN class=029411807-22062006><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=029411807-22062006><FONT face=Arial color=#0000ff
size=2>resolution = 1/dotpitch = 4 pixel/mm = 40 pixel/cm = 40*2,54
pixel/inch = 101,6 pixel/inch = 101,6 dpi</FONT></SPAN></DIV>
<DIV><SPAN class=029411807-22062006><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=029411807-22062006></SPAN><SPAN class=029411807-22062006><FONT
face=Arial color=#0000ff size=2>Set this resolution in your
application.</FONT></SPAN></DIV>
<DIV><SPAN class=029411807-22062006><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=029411807-22062006><FONT face=Arial color=#0000ff size=2>TFT
screens have at native resolution an exact dotpitch that can be found in there
specifications.</FONT></SPAN></DIV>
<DIV><SPAN class=029411807-22062006><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=029411807-22062006><FONT face=Arial color=#0000ff size=2>Good
luck!</FONT></SPAN></DIV>
<DIV><SPAN class=029411807-22062006><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><FONT face=Tahoma><FONT size=2><SPAN class=029411807-22062006><FONT
face=Arial color=#0000ff>[van der Schee,
Maurits] </FONT></SPAN></FONT></DIV>
<DIV><FONT size=2><SPAN
class=029411807-22062006> </SPAN>-----Oorspronkelijk
bericht-----<BR><B>Van:</B> ka-map-users-bounces@lists.maptools.org
[mailto:ka-map-users-bounces@lists.maptools.org]<B>Namens </B>Tim
Schaub<BR><B>Verzonden:</B> woensdag 21 juni 2006 22:18<BR><B>Aan:</B>
ka-Map-users@lists.maptools.org<BR><B>Onderwerp:</B> RE: [ka-Map-users] scalebar
question 1cm = 1km?<BR><B>Urgentie:</B> Laag<BR><BR></DIV></FONT></FONT>
<BLOCKQUOTE dir=ltr style="MARGIN-RIGHT: 0px">
<DIV dir=ltr align=left><FONT face="Trebuchet MS" size=2><SPAN
class=625394919-21062006>Hey Donal-</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face="Trebuchet MS" size=2><SPAN
class=625394919-21062006></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT face="Trebuchet MS" size=2><SPAN
class=625394919-21062006>MapServer assumes a monitor resolution of 72 dpi by
default (so this is what the scale bar assumes by default). This is
seldom correct. The upshot is that the scale ratio (1:1000000) is seldom
correct. However, this doesn't really matter unless you advertise the
scale ratio and a client with a non 72 dpi monitor takes out a
ruler.</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face="Trebuchet MS" size=2><SPAN
class=625394919-21062006></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT face="Trebuchet MS" size=2><SPAN
class=625394919-21062006>There are two things that you can do if this bothers
you.</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face="Trebuchet MS" size=2><SPAN
class=625394919-21062006>1) Guess at your client's resolution and modify the
scale bar's resolution property (myScaleBar.resolution =
96).</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face="Trebuchet MS" size=2><SPAN
class=625394919-21062006>2) Don't tell anybody what the scale ratio of your
map is, and rely on the scale bar for relating display distances to map
distances.</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face="Trebuchet MS" size=2><SPAN
class=625394919-21062006></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT face="Trebuchet MS" size=2><SPAN
class=625394919-21062006>Since people always toss around numbers like 1:250000
for map scales, it might be disappointing to hear that these numbers aren't
generally accurate for monitor displays (since there is not a
reliable way for the server to know the client's screen resolution ahead
of time). This is why I think it's better to rely on a scale bar than a
numeric scale.</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face="Trebuchet MS" size=2><SPAN
class=625394919-21062006></SPAN></FONT> </DIV>
<DIV dir=ltr align=left><FONT face="Trebuchet MS" size=2><SPAN
class=625394919-21062006>Tim</SPAN></FONT></DIV>
<DIV dir=ltr align=left><FONT face="Trebuchet MS" size=2><SPAN
class=625394919-21062006></SPAN></FONT> </DIV><BR>
<BLOCKQUOTE
style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV class=OutlookMessageHeader lang=en-us dir=ltr align=left>
<HR tabIndex=-1>
<FONT face=Tahoma size=2><B>From:</B>
ka-map-users-bounces@lists.maptools.org
[mailto:ka-map-users-bounces@lists.maptools.org] <B>On Behalf Of </B>Donal
Regan<BR><B>Sent:</B> Wednesday, June 21, 2006 1:48 AM<BR><B>To:</B>
ka-Map-users@lists.maptools.org<BR><B>Subject:</B> [ka-Map-users] scalebar
question 1cm = 1km?<BR></FONT><BR></DIV>
<DIV></DIV>Hello all.<BR><BR>I am displaying a map that has amongst it's
scales 1:100000. I would expect my scalebar to show 1cm = 1km, i.e if
I physically measure the scalebar with a ruler, 1cm on the ruler would
correspond to 1km on the scalebar. However, I'm finding that 0.9cm = 1km ,
1.85cm = 2km up to 5.7cm = 6km.<BR><BR><BR> Is this just the way
it is or am I misunderstanding the way the scalebar should be
working?<BR><BR>Cheers,<BR><BR>Donal.<BR><BR>
<P>
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