Re: AVIATIONTOOLBOX: How do you like your maps stitched?

Maybe I'm missing something -- I'll quickly walk you through what I do in
Oziexlporer:
After launching Oziexplorer, I go to the "file" menu, and select "load and
calibrate map image"
This loads the image, but requires that I supply additional data in order to
calibrate the image.

There is an additional menu option to "import map", however, GeoTIFF isn't
an option.

The help screens indicate the following:
*******************help text*****************************
Geotiff
OziExplorer can extract the georeference information from Geotiff files but
it only knows how to decode the information if it is from a known source. At
this stage only the georeference information in the USA USGS DRG Geotiffs
can be decoded.

The ability to decode other sources of georeference information in Geotiff
files will be added on an as need basis where it is possible to do so.


Converting Geotiff Image Files

Some Geotiff Image files are in the 24 bit color format. OziExplorer can
read 24 bit color TIFF files but must load them fully into RAM instead of
paging them from disk as it does with 8 bit color TIFF mages. For large
images this requires a lot of RAM.

If you convert these files to 8 bit color the Geotiff georeference
information is lost.

This document describes a technique to save the georeference information and
to then put it back into the file.

You need

Software to convert the Geotiff image from 24 bit to 8 bit color. Paint Shop
Pro (www.jasc.com) works well.

The Tiff Utilities available from the Utilities section of the OziExplorer
web site (www.oziexplorer.com).

**************end of help text********************

Perhaps the developer of Oziexplorer needs to add these types of files to
its list of "known" types.  I will e-mail them.


"Kyler Laird" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> "Tom Jackson" <[EMAIL PROTECTED]> writes:
>
> >> What do you mean exactly by "After geo-referencing the map files"?
>
> >Well, maybe my terminology is inaccurate, but what I meant to say was, I
> >load, and calibrate the map image.
>
> Nope, your terminology is dead on.
>
> >Basically, I load the map projection
> >information into the program (i.e., Lambert Conformal Conic, with the
> >appropriate lat/lon info.) I got this information from one of the HTML
files
> >related to the specific map TIFF.
>
> Stop doing that!  The sectionals are already GeoTIFFs.  The FAA has
already
> done all of that work for us.  (They guarantee 2 pixels RMS error, but
I've
> found distortions much greater than that.)
>
> I'm also working on making more easily-digested chunks of data.  If you're
> in the mood to burn some time and bandwidth, you can watch my progress.
> http://aviationtoolbox.org/munge/mosaic.cgi
> Just change the extension to ".tif" on any of the images if you want a
5000
> by 5000 uncompressed GeoTIFF.
>
> (I need to tweak my edge-detection algorithm.  When I do, I'll clear those
> images and start over but you're welcome to try it anyway.)
>
> --kyler