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| GeoCommunity Mailing List |
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| Mailing List Archives |
| Subject: | Re: GISList: GeoTIFF Headers |
| Date: |
04/11/2003 12:05:01 PM |
| From: |
northms .. telus.net |
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Andy,
Sorry to say, I can't shed any light on the problem you are having... I am
still kinda confused about how the AUX file works. I hope someone else can
enlighten us.
We don't have ArcInfo 8, just ArcView 8. So the CONVERTIMAGE command Toby
mentions isn't available. If I need to override the GeoTIFF header
information, I open the TIFF in an image editing program (PaintShopPro) and
resave it under a different name: this seems to eliminate the header. Then I
create a TFW, as well as defining the projection via ArcCatalog. Not very
efficient for multiple images, but I haven't found another approach without
requiring more software.
A related annoyance: ArcView 3.x would read coordinate information from an
image catalog DBF table, overriding GeoTIFF and TFW information. You can use
the same image catalog in ArcMap 8.x, but it seems to read the coordinate
information from each image's GeoTIFF header or TFW, not from the catalog table.
sarah
Quoting Toby L Welborn <tlwelbor@usgs.gov>:
>
> We had a similar problem. We, I say we because there was a whole team
> working, found that a GeoTIFF saved space over a raster format or a regular
> TIFF if it was a small image. We also found that doing a simple
> CONVERTIMAGE from the command line fixed any projection issues between
> ArcVIew 3.X and ArcGIS 8.X and did not create any size issues.
>
> Attached are two links to ESRI Help dealing with image "conversion"
>
> http://support.esri.com/search/KbDocument.asp?dbid=16192
>
> http://support.esri.com/search/KbDocument.asp?id=22490
>
> Go
>
> Toby Welborn
> tlwelbor@usgs.gov
>
>
> |---------+---------------------------->
> | | "Andy Morris" |
> | | <Andy.Morris@Merr|
> | | ick.com> |
> | | |
> | | 04/11/2003 08:39 |
> | | AM |
> | | |
> |---------+---------------------------->
>
> >-----------------------------------------------------------------------------
-------------------------------------|
> |
> |
> | To: <northms@telus.net>
> |
> | cc: <gislist@geocomm.com>
> |
> | Subject: GISList: GeoTIFF Headers
> |
>
> >-----------------------------------------------------------------------------
-------------------------------------|
>
>
>
>
> Sarah,
> I read the ESRI support pages you listed and they were informative, but I
> would like to dig a little deeper and see if you have any further insight
> into GeoTIFFs. The second document listed states that "ArcGIS does not
> provide a mechanism to alter the GeoTIFF tags that control the internal
> georeferencing of TIFF images." However, when I define spatial reference
> information for a GeoTIFF a temporary file is created that grows in size
> until it matches the original GeoTIFF image size then it is removed and the
> original GeoTIFF's modified date/time changes and the file is 1 KB larger
> than it was before I defined the spatial reference information. I can then
> delete the corresponding .aux file and still list the projection
> information through ArcCatalog-->properties for that image. At no point is
> there a world file created. This would appear to mean that you don't have
> to do the image --> grid then grid --> image manipulation after all. I dug
> this deep because we are producing GeoTiffs for the USGS and the header
> contains some custom information that I want to preserve after metadata
> creation that needs spatial reference information. Anybody really know
> what is happening?
>
> Cheers,
> Andy Morris
> GIS Supervisor
> Merrick & Company
> andy.morris@merrick.com <mailto:andy.morris@merrick.com>
>
> Original reply:
> Monica,
>
> One possible source of your problem: ArcView 8.x does not read coordinate
> system information for an image in the same way that ArcView 3.x does. For
>
> example, what if the image is a GeoTIFF file (with coordinate system
> information embedded in the TIFF file) but you also have a world file (TFW)
>
> with different coordinate system information? ArcView 3.x will read the
> TFW
> first, but ArcView 8.x will read the GeoTIFF embedded information fi
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