One thing that is notably missing from the site or software documentation
(what's that?) is a description of what tiff variants work best and any
caveats. I have extreme grief trying to make geotiff images I download from a
state repository work as a map collection.
Things that should be explicitly addressed are
1) whether transparency or alpha channels are supported
2) any realistic resolution or image size constraints
3) is indexed or RGB(A) preferred?
4) whether speific DATUM specification enjoy better or worse
integration/support in the program: NAD27, WGS84, UTM, etc...since a LOT of my
availble images are only available in old NAD27, yet I have to make them work
in a WGS84 world.
5) MINIMUM geotiff tags that must be present
6) a better understanding of whether a tfw file can be used in lieu of manually
georeferencing an image with control points
Another thing that should really exist, if it doesn't already, is an
environment variable to control debug output of all the behind-the-scenes gdal
processing that goes on. a simple "cannot read xyz.tif?" error message is not
sufficient to figure out why the error occured.
Below is the listgeo and tiffinfo dump from a TIFF that works in the system,
followed by the dump of one that is not recognized. What is the key difference
that keeps the second one from working?
WORKS!-----------------------------------------------------------------
$> listgeo ../WV/whitmer_ref.tif
TIFFReadDirectory: Warning, Unknown field with tag 42113 (0xa481) encountered.
Geotiff_Information:
Version: 1
Key_Revision: 1.0
Tagged_Information:
ModelTiepointTag (2,3):
0 0 0
-79.6250592 38.875044 0
ModelPixelScaleTag (1,3):
4.89618369e-05 4.89618369e-05 0
End_Of_Tags.
Keyed_Information:
GTModelTypeGeoKey (Short,1): ModelTypeGeographic
GTRasterTypeGeoKey (Short,1): RasterPixelIsArea
GeographicTypeGeoKey (Short,1): User-Defined
GeogCitationGeoKey (Ascii,83): "GCS Name = unnamed ellipse|Datum =
unknown|Ellipsoid = unnamed|Primem = Greenwich|"
GeogGeodeticDatumGeoKey (Short,1): User-Defined
GeogAngularUnitsGeoKey (Short,1): Angular_Degree
GeogEllipsoidGeoKey (Short,1): User-Defined
GeogSemiMajorAxisGeoKey (Double,1): 6378206.4
GeogInvFlatteningGeoKey (Double,1): 294.978698
GeogPrimeMeridianLongGeoKey (Double,1): 0
Unknown-2062 (Double,3): -8 160 176
End_Of_Keys.
End_Of_Geotiff.
Corner Coordinates:
Upper Left ( 79d37'30.21"W, 38d52'30.16"N)
Lower Left ( 79d37'30.21"W, 38d44'59.81"N)
Upper Right ( 79d29'58.98"W, 38d52'30.16"N)
Lower Right ( 79d29'58.98"W, 38d44'59.81"N)
Center ( 79d33'44.60"W, 38d48'44.98"N)
$> tiffinfo ../WV/whitmer_ref.tif
TIFFReadDirectory: Warning, Unknown field with tag 33550 (0x830e) encountered.
TIFFReadDirectory: Warning, Unknown field with tag 33922 (0x8482) encountered.
TIFFReadDirectory: Warning, Unknown field with tag 34735 (0x87af) encountered.
TIFFReadDirectory: Warning, Unknown field with tag 34736 (0x87b0) encountered.
TIFFReadDirectory: Warning, Unknown field with tag 34737 (0x87b1) encountered.
TIFFReadDirectory: Warning, Unknown field with tag 42113 (0xa481) encountered.
TIFF Directory at offset 0x8 (8)
Image Width: 2560 Image Length: 2555
Tile Width: 256 Tile Length: 256
Bits/Sample: 8
Sample Format: unsigned integer
Compression Scheme: AdobeDeflate
Photometric Interpretation: RGB color
Extra Samples: 1<assoc-alpha>
Samples/Pixel: 4
Planar Configuration: single image plane
Tag 33550: 0.000049,0.000049,0.000000
Tag 33922: 0.000000,0.000000,0.000000,-79.625059,38.875044,0.000000
Tag 34735:
1,1,0,11,1024,0,1,2,1025,0,1,1,2048,0,1,32767,2049,34737,83,0,2050,0,1,32767,2054,0,1,9102,2056,0,1,32767,2057,34736,1,0,2059,34736,1,1,2061,34736,1,2,2062,34736,3,3,0,0,0,0
Tag 34736: 6378206.400000,294.978698,0.000000,-8.000000,160.000000,176.000000
Tag 34737: GCS Name = unnamed ellipse|Datum = unknown|Ellipsoid =
unnamed|Primem = Greenwich||
Tag 42113: 255
Predictor: none 1 (0x1)
TIFFReadDirectory: Warning, Unknown field with tag 42113 (0xa481) encountered.
TIFF Directory at offset 0x9b3b00 (10173184)
Subfile Type: reduced-resolution image (1 = 0x1)
Image Width: 1280 Image Length: 1278
Tile Width: 128 Tile Length: 128
Bits/Sample: 8
Sample Format: unsigned integer
Compression Scheme: AdobeDeflate
Photometric Interpretation: RGB color
Extra Samples: 1<assoc-alpha>
Samples/Pixel: 4
Planar Configuration: single image plane
Tag 42113: 255
Predictor: none 1 (0x1)
TIFFReadDirectory: Warning, Unknown field with tag 42113 (0xa481) encountered.
TIFF Directory at offset 0x9b3ef6 (10174198)
Subfile Type: reduced-resolution image (1 = 0x1)
Image Width: 640 Image Length: 639
Tile Width: 128 Tile Length: 128
Bits/Sample: 8
Sample Format: unsigned integer
Compression Scheme: AdobeDeflate
Photometric Interpretation: RGB color
Extra Samples: 1<assoc-alpha>
Samples/Pixel: 4
Planar Configuration: single image plane
Tag 42113: 255
Predictor: none 1 (0x1)
TIFFReadDirectory: Warning, Unknown field with tag 42113 (0xa481) encountered.
TIFF Directory at offset 0x9b4094 (10174612)
Subfile Type: reduced-resolution image (1 = 0x1)
Image Width: 320 Image Length: 320
Tile Width: 128 Tile Length: 128
Bits/Sample: 8
Sample Format: unsigned integer
Compression Scheme: AdobeDeflate
Photometric Interpretation: RGB color
Extra Samples: 1<assoc-alpha>
Samples/Pixel: 4
Planar Configuration: single image plane
Tag 42113: 255
Predictor: none 1 (0x1)
TIFFReadDirectory: Warning, Unknown field with tag 42113 (0xa481) encountered.
TIFF Directory at offset 0x9b41b2 (10174898)
Subfile Type: reduced-resolution image (1 = 0x1)
Image Width: 160 Image Length: 160
Tile Width: 128 Tile Length: 128
Bits/Sample: 8
Sample Format: unsigned integer
Compression Scheme: AdobeDeflate
Photometric Interpretation: RGB color
Extra Samples: 1<assoc-alpha>
Samples/Pixel: 4
Planar Configuration: single image plane
Tag 42113: 255
Predictor: none 1 (0x1)
TIFFReadDirectory: Warning, Unknown field with tag 42113 (0xa481) encountered.
TIFF Directory at offset 0x9b42a8 (10175144)
Subfile Type: reduced-resolution image (1 = 0x1)
Image Width: 80 Image Length: 80
Tile Width: 128 Tile Length: 128
Bits/Sample: 8
Sample Format: unsigned integer
Compression Scheme: AdobeDeflate
Photometric Interpretation: RGB color
Extra Samples: 1<assoc-alpha>
Samples/Pixel: 4
Planar Configuration: single image plane
Tag 42113: 255
Predictor: none 1 (0x1)
BROKEN! ----------------------------------------------------------------
$> listgeo sigel_pa_ref.tif
Geotiff_Information:
Version: 1
Key_Revision: 1.0
Tagged_Information:
ModelTiepointTag (2,3):
0 0 0
656801.062 4582106.46 0
ModelPixelScaleTag (1,3):
2.4384 2.4384 0
End_Of_Tags.
Keyed_Information:
End_Of_Keys.
End_Of_Geotiff.
Corner Coordinates:
Upper Left ( 656801.062, 4582106.459)
Lower Left ( 656801.062, 4567993.000)
Upper Right ( 667576.352, 4582106.459)
Lower Right ( 667576.352, 4567993.000)
Center ( 662188.707, 4575049.730)
$> tiffinfo sigel_pa_ref.tif
TIFFReadDirectory: Warning, Unknown field with tag 33550 (0x830e) encountered.
TIFFReadDirectory: Warning, Unknown field with tag 33922 (0x8482) encountered.
TIFF Directory at offset 0x8 (8)
Image Width: 4419 Image Length: 5788
Resolution: 72, 72 pixels/inch
Bits/Sample: 8
Sample Format: unsigned integer
Compression Scheme: None
Photometric Interpretation: RGB color
Extra Samples: 1<assoc-alpha>
Samples/Pixel: 4
Rows/Strip: 1
Planar Configuration: single image plane
DocumentName: /WD3TB/GPS/maps/CooksForest/sigel_pa_transparent.tif
Tag 33550: 2.438400,2.438400,0.000000
Tag 33922: 0.000000,0.000000,0.000000,656801.062500,4582106.459200,0.000000
------------------------------------------------------------------------------
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