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<p class=MsoNormal><st1:City w:st="on"><st1:place w:st="on"><font size=2
color=navy face=Arial><span style='font-size:10.0pt;font-family:Arial;
color:navy'>Duncan</span></font></st1:place></st1:City><font size=2
color=navy face=Arial><span style='font-size:10.0pt;font-family:Arial;
color:navy'>,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>There isn’t a limit that is specific
to GeoTIFF but computers in general have limitations in their standard floating
point representations. In the small image, the UTM projection in combination
with the small image area means that the difference between the coordinates in
adjacent pixels doesn’t show up until the tenth decimal place. This is
not a problem if double precision floating point numbers (64-bit quantities) are
used (where 17 decimal digits of precision can be accommodated), but if floats (32-bit
quantities) are used anywhere in these software products, you may see funny
behavior.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>ERDAS IMAGINE seems to display the images
OK ;-)<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Max<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>
geotiff-bounces@lists.maptools.org [mailto:geotiff-bounces@lists.maptools.org] <b><span
style='font-weight:bold'>On Behalf Of </span></b>Duncan Mercer<br>
<b><span style='font-weight:bold'>Sent:</span></b> Tuesday, July 22, 2008 8:51
PM<br>
<b><span style='font-weight:bold'>To:</span></b> geotiff@lists.maptools.org<br>
<b><span style='font-weight:bold'>Subject:</span></b> [Geotiff] Geotiff problem
with "small" images???</span></font><o:p></o:p></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Hi <br>
<br>
I'm new to the world of geotiff and I'm running<br>
into a problem when generating small area coverage<br>
geotiffs<br>
<br>
I'm collecting images using a robotic submarine (an AUV)<br>
and want to use geotiff to locate these images for use in a<br>
GIS etc. Typical footprint for the images is 1m x 1.5m<br>
<br>
If I write the geotiff tags using the correct size then the<br>
image appears badly distorted when viewed in openev and<br>
in arcgis. If however I keep everything else the same and <br>
pretend that the image is 1Km x 1.5Km the image will appear<br>
undistorted.<br>
<br>
Has anyone come across this issue before, is there some fundamental<br>
lower limit on the image size that I've not picked up on? Or can someone<br>
tell me how to search the mailing list archives for similar issues?<br>
<br>
Example images are available at.<br>
<a href="http://www-personal.acfr.usyd.edu.au/d.mercer/geotiff">http://www-personal.acfr.usyd.edu.au/d.mercer/geotiff</a><br>
Large image appears ok, but oversized. Small image is distorted<br>
(at least in openev. I haven't been able to check this one in arcgis<br>
but I have seen the issue with other images I have generated in the past)<br>
<br>
<br>
<br>
<br>
FYI.<br>
I am using libgeotiff and writing the following geotags...<br>
<br>
TIFFSetField(tif_ptr, TIFFTAG_GEOTRANSMATRIX, 16, position.transform); <br>
<br>
GTIFKeySet(gtif_ptr, GTModelTypeGeoKey, TYPE_SHORT, 1,
ModelTypeProjected);<br>
GTIFKeySet(gtif_ptr, GTRasterTypeGeoKey, TYPE_SHORT, 1,
RasterPixelIsArea);<br>
<br>
GTIFKeySet(gtif_ptr, ProjectedCSTypeGeoKey, TYPE_SHORT, 1, utm_zone);<br>
GTIFKeySet(gtif_ptr, PCSCitationGeoKey, TYPE_ASCII,
PCS_Zone.str().length(), PCS_Zone.str().c_str());<br>
<br>
<br>
Any help or suggestions gratefully received.<br>
Best regards<br>
<st1:City w:st="on"><st1:place w:st="on">Duncan</st1:place></st1:City><br>
<br>
<br>
-- <br>
Dr Duncan Mercer<br>
Australian Centre for Field Robotics<br>
The <st1:place w:st="on"><st1:PlaceName w:st="on">Rose</st1:PlaceName> <st1:PlaceName
w:st="on">Street</st1:PlaceName> <st1:PlaceType w:st="on">Building</st1:PlaceType></st1:place>,
J04<br>
The <st1:place w:st="on"><st1:PlaceType w:st="on">University</st1:PlaceType> of
<st1:PlaceName w:st="on">Sydney</st1:PlaceName></st1:place>.<br>
2006 NSW, <st1:country-region w:st="on"><st1:place w:st="on">Australia</st1:place></st1:country-region><br>
Tel: +61 (0) 2 9036 7178<br>
Fax: +61 (0) 2 9351 7474 <o:p></o:p></span></font></p>
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