Hello:
Your posting history makes it clear that you have experience in 3D modeling and texturing for a FS development project, and that this is perhaps your first attempt at making textures for the FS terrain.
It also is apparent that you may have utilized some aerial imagery in GeoTiff format during your 3D modeling for the Arlanda airport project, and the *.TFW files may have been separated from the original *.TIF files.
There a number of ways to texture the FS "
terrain mesh" ground surface, all of which require that the aerial imagery source data is "Geo-referenced" for use with the FS SDK compilers; custom photo-real "mesh-clinging" aerial imagery ground textures placed via a BGL is indeed (1) of those methods.
Those
terrain mesh ground surface texturing methods are to be distinguished from texturing "flat" 3D planar objects in a 3D modeling application and placing it in FS via "scenery object methods".
FYI: While is generally true that
GeoTiff files by definition may have "all" required info for Geo-referencing inside the (specially formated)
*.TIF file itself, they are often
purposefully distributed with
ex:
*.TFW "world" files and
*.PRJ "projection" files ...for use in some GIS-type applications.
IMHO these associated
*.TFW "world" files and
*.PRJ "projection" files should '
always' be kept in the
same folder with the
same 'original' GeoTiff to which they pertain ...in the event they may be needed for use with certain GIS and/or FS development utilities.
IMHO, it is a prudent procedure to keep
backups of
all original source files
before / during / after any conversion and editing.
Then, working with
copies of the originals, one must back up the geo-referencing info contained in the Geo-TIFF and its accompanying files using an appropriate GIS utility
before editing the
ex: aerial imagery within it using a graphics editor
ex: GIMP, or the geo-referencing info (and other metadata) may be corrupted and/or removed ...when the edits are saved back into the Geo-TIFF by the graphics editor.
There are numerous threads regarding this process here at FSDeveloper which you may wish to review; IMHO using Google's search with multiple word query strings may find such threads fairly quickly,
ex:
http://www.fsdeveloper.com/forum/threads/strange-output-coordinates-after-resample.432724/
https://www.google.com/#q=fsdeveloper GaryGB geoTIFF Geo-TIFF world file
Hope this helps with the learning process !
GaryGB