GeoTIFF export

sonny

Hello,

I already exported many different kinds of topographic maps, my prefered raster format to export is GeoTIFF. I achieve satisfying results for 8bit maps as well as 24bit shaded relief maps. Yes - even 24bit JPEG compressed topographic maps finally reach the same size and quality like the typical 24bit format ECW :cool:.

During my work I noticed the following things which could be fixed to improve GeoTIFF export:

1.
ZIP-Compression

Please add ZIP-Compression, it's a well known compression for GeoTIFFs (e.g. photoshop etc.) and LOSSLESSLY saves about 20% space compared to LZW.


2.
Let User choose between Normal TIFF or BigTIFF

Well, this is already used for large 8bit exports when the user is asked.
But when exporting large 24bit-maps, the window just lets me choose from
a) YES - Continue with Export as BigTIFF
b) NO - Abort Export
Even if the resulting file would be <4GB, the maximum size for Normal TIFF. BigTiff is not being read by every software, so please let the user decide to export as Normal TIFF too like with 8bit.

3.
Improve JPEG-in-TIFF Compression

JPEG-Compression is ideal for 24bit-Exports. But i noticed that GM produces about 200% larger files than JPEG-in-TIFFs produced with another geo-software. Of course both with identical resulting quality with hardly no artefacts (85% setting in the registry for Global Mapper). Example: 27MB vs. 13MB
For comparision I also exported my map as standard JPEG with GlobalMapper, Image quality 90% (which again results in the same quality as the JPEG-in-TIFFS) and now the filesize is shrunken significantly to 12 MB .
So the standard JPEG-export of Global Mapper works good but there's somthing wrong with the JPEG-in-TIFF export.


4.
Add a quality slider for JPEG-in-TIFF

it's such an important factor, and has to be changed for nearly every map to reach a desired quality, less artefacts and less filesize. Don't hide it in the registry like now but make it easy reachable within the export dialog like for standard JPEG-exports


Would be great for GeoTIFF exports if you could implement these points, thank you!

global_mapper

I'll take a look at adding support for Deflate compression (the .zip compression in other software), I didn't realize it was significantly better than LZW.

I should also be able to add an option to continue 24-bit compressed export as regular rather than BigTIFF and add a JPEG-in-TIFF quality slider. I'll let you know when support is added.

Thanks,

Mike
Global Mapper Support
support@globalmapper.com

global_mapper

I have updated Global Mapper to support the Deflate (ZIP) compression method (in my tests it was very close to LZW in size, although I didn't try a lot of different data sets). I also added a place to set the JPEG-in-TIFF quality setting when exporting to GeoTIFF and made the BigTIFF prompt allow exporting normal GeoTIFF even for files with more than 4 billion pixels if there is any compression being used.

I have placed a new build at http://www.globalmapper.com/global_mapper12.zip with these changes for you to try. Simply download that file and extract the contents into your existing v12.xx installation folder to give it a try. If you are using the 64-bit v12 version there is a new build at http://www.globalmapper.com/global_mapper12_64bit.zip .

Let me know if I can be of further assistance.

Thanks,

Mike
Global Mapper Support
support@globalmapper.com

sonny

Mike, thanks for the quick realisation of the new GeoTIFF Features

Is it finally possible for you to improve the quality of JPEG-in-TIFF compression? Compared with the JPEG-alone export of GM it compresses just about half the rate for reaching the same optical quality. I don't think that this enourmous difference is just the overhead of GeoTiff file format.

For example a map is compressed to 4 GB JPG-in-TIFF. The same map with JPG-alone export is compressed down to 2 GB with the same optical quality.

For 24-bit maps JPEG-in-Tiff is the one and only useful compression. It creates well compressed maps with an adjustable quality and finally has all the GeoTIFF advantages.
It would be a waste of space if such a map needs unnecessarily double the size or the user has to split the map.

global_mapper

Can you provide one of the JPEG-in-TIFF files created by other geo-software that is smaller? I can't seem to find anything that would cause the GM created ones to be so much larger, but they obviously are, at least compared to normal JPEG.

Thanks,

Mike
Global Mapper Support
support@globalmapper.com

global_mapper

I was able to update the JPEG-in-TIFF export to use the proper color encoding and get much better compression (should be 2-3 times better!). I have placed a new build at http://www.globalmapper.com/global_mapper12.zip with the change for you to try. Simply download that file and extract the contents into your existing v12.xx installation folder to give it a try. If you are using the 64-bit v12 version there is a new build at http://www.globalmapper.com/global_mapper12_64bit.zip .

Let me know if I can be of further assistance.

Thanks,

Mike
Global Mapper Support
support@globalmapper.com

abarefoot1

Hello Mike,

In response to the original post (suggestion 2), I am exporting an 8-bit pallete image GeoTIFF with no compression and for a large area, and after selecting NO - Abort Export I still receive the BigTIFF metadata tag in the output file.  I thought that aborting the export would keep the file in a GeoTIFF format rather than BigTIFF.  Am I missing something on my end?

Thanks in advance!