Zooming on images
Stephen Lime
steve.lime at dnr.state.mn.us
Mon Sep 20 13:10:27 PDT 1999
Um, er... Scale calculations with DD data are broken. That is, since
x cellsize (no straight DD/in conversion) varies I didn't add the s
upport to calculate some average scale even though it's just an
approximation. I got some equations from the guys at Space Imaging
and have added scale calculation support for DD units to the new
version. With that version you'll be able to do exactly what you propose
with the layer descriptions below.
** Note **
I'm interested in users opinions on this. Should scale for DD maps
be constant at a given zoom for anywhere on the globe (i.e. based
on cellsize in the y direction) or should it vary as you pan north or
south (i.e. based on the average cellsize in the x direction), or should it
be computed as some sort of average of the computed cellsize in
both directions? I'm leaning towards just using an average x cellsize
but am open to other points of view.
** end **
The scale problem only effect the minscale/maxscale piece but
you should be able to zoom in and out. (you'll have to pick an image
to use). You might try commenting out the minscale/maxscale stuff
and turning all rasters off except for 1 and see if that helps.
Got a "get" URL I can play with?
Steve
Stephen Lime
Internet Applications Analyst
MIS Bureau - MN DNR
(651) 297-2937
steve.lime at dnr.state.mn.us
>>> ddnebert <ddnebert at usgs.gov> 09/20 2:45 PM >>>
I have now four nice TIF images that I would like to use as backdrop to
other
data. The files are as follows with wld files that let them render fine
individually
at full extent. If I try to set another extent in the GET request, I
still see the
whole world, rather than a zoomed in region.
shdrela.tif 640 x 320 TIF
shdrelb 2160 x 1080 TIF
shdrelc 4800 x 2400 TIF
shdreld 10800 x 5400 TIF
So I have two problems:
1. How do I make the registration correct? I calculated the TFW files
as attached.
2. Once I can view one of the files, I'd like to set them up as a
cascade
of a single theme, broken by MINSCALE and MAXSCALE values.
Should the following work?
LAYER
NAME shdrelief
TYPE RASTER
STATUS ON
DATA shdrela.tif
MINSCALE 5000000
OFFSITE 0
END
LAYER
NAME shdrelief
TYPE RASTER
STATUS ON
DATA shdrelb.tif
MINSCALE 3000000
MAXSCALE 5000000
OFFSITE 0
END
LAYER
NAME shdrelief
TYPE RASTER
STATUS ON
DATA shdrelc.tif
MINSCALE 1000000
MAXSCALE 3000000
OFFSITE 0
END
LAYER
NAME shdrelief
TYPE RASTER
STATUS ON
DATA shdreld.tif
MAXSCALE 1000000
OFFSITE 0
END
More information about the MapServer-users
mailing list