Export imported ECW images

withnailwithnail Global Mapper UserPosts: 3
edited June 2008 in Raster Data
I've imported some images using the "open ECW file from the web" command. These tiles opened fine.

However, when I try to export them as GeoTiff's the export seems to take a really, really long time. In fact, unless I break the image into extremely small tiles using the grid function, the export pretty much freezes on 0%. I've tried leaving it for an hour or so but it only just makes it to 1% or 2%.

I've exported much bigger GeoTiff files before now pretty quickly. Is there something particular about the ECW files that I need to be aware of?

I've tried exporting as 8-bit, which did not make any difference.

Thanks

Comments

  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited June 2008
    What is almost certainly slowing things down is the access over the web. The export speed in this case will almost entirely depend on how fast the web server hosting the ECW file is serving it up for export. The export will most likely be an order of magnitude (or more!) slower than exporting from an ECW file found directly on your computer. If it is possible for you to download a local copy of the image prior to converting to GeoTIFF, that would be recommended.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • withnailwithnail Global Mapper User Posts: 3
    edited June 2008
    Forgive my ignorance, but how do I do that?

    Originally, I imported the files using the 'File-> Open ECW file from the web' command. Once I have the colour image in my Global Mapper view, is there then a way to then save those ECW files onto my computer from Global Mapper?

    Thanks
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited June 2008
    The server from which you are obtaining the ECW file over the web connection would need to have a separate download for it somewhere, or else you would have to obtain it from some different site.

    Note that when you are viewing an ECW file from the web in Global Mapper, only the portion of the ECW file required for viewing is being accessed from the server. This will typically be data from a much lower zoom level than required for export (which will default to the full resolution of the file), thus requiring much less data to be downloaded than for export. To get an idea of how much data must be downloaded for export, you would need to zoom in on the image until the full detail of the image was visible, then pan around until you had looked at the entire image.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
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