MapInfo rasters to GeoTIFF

A tiny piece of Polish software came to the rescue. At MapAction, we had a request yesterday from our field team in Papua New Guinea for help with converting TIFF files whose georegistration parameters are saved MapInfo format (.TAB file) to something compatible with ArcGIS.

It’s not a complicated task: TAB files are easy to read, and all that’s needed is to calculate the relevant parameters for a TFW file to accompany the TIFF.

The field team doesn’t have MapInfo installed, so a solution needing MI is out. Ideally, we wanted a free solution, ruling out the excellent Global Mapper, for example. Any download had to be as small as possible thanks to limited internet access. And finally, although the team has ArcEditor, they don’t have a license for Data Interoperability Extension, so that wasn’t an option.

After quite a lot of searching, I was pleased to find this neat and effective utility:
http://www.npgc.pl/english/free_GIS_GTT_convert_tfw_tab_geotif.htm

It does the job, and best of all, it’s “postcardware” – I hope a postcard will be arriving in Gdansk from Papua New Guinea soon (depending on the post).

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5 responses to “MapInfo rasters to GeoTIFF

  1. HI, interesting post. How accurate is the conversion? I have used FWtools to generate world files from Mapinfo tiff files but the accuracy is quite poor. I was under the impression that the differences in raster registration between the different software’s means that a direct translation is difficult without loosing accuracy. Especially for older mapping that has transform and skew to the maps (mapinfo cannot turn maps but instead re-projects the vector maps that overlay the rasters).

    Mapaction is a very good cause to be helping with!

  2. Thanks for the comment Mark. I’m not sure I can give you a good answer, I’m afraid. In our particular case, the method proved accurate. However, the raster images didn’t require any rectification – it was simply a matter of georegistering them – so perhaps there was less scope for error.

    In principle, however, is there any reason why converting between raster formats would lead to coordinate inaccuracies? I can’t think of any particular reason, provided that the respective coordinate system formats are known and adhered to by the conversion software.

    In my experience, most coordinate system errors arise from the datums that are either incorrectly specified, or not specified at all and hence taking on a default datum setting.

    Please let us know how you get on!

  3. HI Nick,
    Thanks for your reply. I think the major issue is the way in which Mapinfo and Arc project images. Mapinfo doesn’t apply transform to the images (correct me if I am wrong here this is my understanding of how it works) and it re-projects all vector maps on top of the rasters. Arc can transform images and will turn twist and warp images as needed during geo-referencing. I have found that older non-national grid mapping which is converted just using mapinfo tab to world file conversion is really inaccurate. At present the only solution that I know works with a tolerable accuracy error margin is to generate geotiffs.

    I will read your other posts, have you helped Mapaction since?

    • Thanks for that Mark – all makes sense to me. Yes, still very much involved with MapAction – we have two missions about to start, relating to Syria/Turkey and Central African Republic.

  4. Hi, I’ve found this post by incident. To close the loop: yes, the postcard from Papua New Guinea has arrived to Gdansk, right on my desk 🙂 Regards!

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