>We have digitized many high resolutions maps of scale 1: 600
>The width of the map is 1300 feet and the height 900 feet.
>After the raster has been registered in non earth feet, the
>on screen measurement of the raster and vector is 1300/900.
>
>But when we take a print out in the same scale 1: 600 on a
>HP 750C Designjet Plotter and measure the same with a scale
>(that is measuring on the paper the conversion comes to
>1297/905) and moreover this measurement is different for
>different maps. Sometimes increasing sometimes decreasing.
>But onscreen measurement is always correct.
>
>Can any one explain this behaviour ?
Sounds like your plotter may need a belt and/or some gears
changed. Over time they wear and cause distortion.
There are a couple of methods for determining if the plotter is
at fault or not. One is to plot one map/image, rotate it 90°,
and then plot it again. Measure both plots and see if the
compression axis changes (map is shorter across the width or
the height than it should be).
If the the plot is compressing left and right (relative to the print
head), the long belt & gears which move the print head across
are worn and need replacing.
If plot is compressing along the long axis, the paper feed gears
are worn and need to be replaced.
It's been a long time since I used the 750, so my memory is
fuzzy, but there should be an accuracy or calibration plot setting
under the Utilities menu (via front panel on plotter). One of these
will plot an E sized grid pattern, which you then load into the
plotter so it can attempt to recalibrate itself. If the belts & gears
are not too worn, the plotter can probably adjust for the the wear.
In a normal setting, the plotter should be recalibrated every X
number of plots or once every month or two (basically:
periodically measure the plots and recalibrate when necessary).
My advice is to try and recalibrate the plotter. If that does not
work, get an HP technician in to service the plotter and carefully
watch what s/he does. Ask them questions and get them to
explain. Before s/he leaves, buy an extra belt kit and their high
quality moly grease. This way you should only have to call them
in every second or third year instead of every year.
cheers,
-matt
----------------------------------------------------------------------
To unsubscribe from this list, send e-mail to [EMAIL PROTECTED] and put
"unsubscribe MAPINFO-L" in the message body, or contact [EMAIL PROTECTED]
