Georeferencing Maps [was GPS and airspace]

Hello Tom,

Thanks for the tips. I found that when I use the "raw data" it does work as
you say (http://aviationtoolbox.org/raw_data/...onals/current/). Is
this what you are using?

But I have trouble when I try to use one of Kyler's "processed images" from
https://aviationtoolbox.org/Members/...s/map_explorer
I have the problems that J.G. diagnoses below.

Kyler, are you out there? does any of that make sense to you?

(The example that I was using was
https://aviationtoolbox.org/Members/...ols/map_image?
scale=50&image_format=GeoTIFF&lr_Y=-
792315.0&lr_X=352633.0&ul_X=250233.0&ul_Y=-715515.0)

Cheers,
John Clonts
Temple, Texas
N7NZ




"Tom Jackson" wrote in message
news:KnHDc.190504$Ly.84959@attbi_s01...
I'm using version 3.95.3e of Oziexlplorer (commercial version, not demo.)

I download the TIF file from Kyler's website into a folder.

In Ozi, I choose file|Import Map|Single DRG (Or, all DRG . . .) It asks a
few questions, such as file location, etc. and automatically imports and
calibrates the image.

When I first got Ozi, it didn't work so I e-mailed them. Des, the
creator,
e-mailed me back that he had updated the program to handle these types of
files, and that I should download the most current version. I did, and it
worked great. When I download waypoints (i.e., airports, using
http://navaid.com/GPX/) it shows them almost exactly on top of the ones
depicted on the map. Some are off slightly, but I don't use it for any
real
navigation - just for fun.

I have actually used it a few times in the plane, works well as a moving
map. Will automatically pan from one sectional to the other, as I cross
boundries. The Terminal charts are also geo-referenced, and Ozi can
import
them as well. Can draw routes, etc. or download them from the GPS. I use
a
simple Garmin GPS III (not the Pilot version.)

"John Clonts" wrote in message
...

"Tom Jackson" wrote in message
newsw6Dc.95742$2i5.90727@attbi_s52...
Try Oziexplorer (www.oziexporer.com,) and scanned FAA sectionals
provided
by
Kyler Laird at aviationtoolbox.org.

The sectionals are "geo-tiffs" and Oziexplorer can import them and
automatically scale them to the proper lat/lon.


Have you actually done this? It didn't work for me-- the georeferencing
nor
the image display. I posted to the Ozi-Users email list and got the
response below.

I would sure like to get it to work, so if you have some tips please let
me
know at jclonts AT hot DOT rr DOT com.

Cheers,
John Clonts
Temple, Texas


Date: Sun, 20 Jun 2004 19:05:18 -0000
From: "rwcx183" xyzzy
Subject: GeoTiff support?

John,

There's more than 1 problem with what you're trying to do. Firstly,
the Geotiff tags for this image specify that the image is in Lambert
Conformal Conic projection and Ozi cannot (to my knowledge) handle
that projection on import. You can try to use Albers (equal area) as
an alternative, since it has the same set of required parameters.
That sometimes results in acceptable accuracy, but sometimes not
(this case). You can also manually calibrate the map image using the
just the upper left and lower right corners as cal points. You will
have to convert the lambert grid coordinates for the corners to
lat/lon or UTM first though, since Ozi doesn't allow specifying
coordinates in Lambert grid. That Ozi does not support Lambert
Conformal Conic projection on import, is the most glaring omission,
in an otherwise very capable program. That and the non-support of
any linear unit besides meters, for georef coordinates. Here's the
Geotiff dump of the georeferencing info for your image:

Geotiff_Information:
Version: 1
Key_Revision: 1.0
Tagged_Information:
ModelTiepointTag (2,3):
0 0 0
250233 -715515 0
ModelPixelScaleTag (1,3):
128 128 0
End_Of_Tags.
Keyed_Information:
GTModelTypeGeoKey (Short,1): ModelTypeProjected
GTRasterTypeGeoKey (Short,1): RasterPixelIsArea
GTCitationGeoKey (Ascii,8): "unnamed"
GeographicTypeGeoKey (Short,1): GCS_NAD83
ProjectedCSTypeGeoKey (Short,1): User-Defined
ProjectionGeoKey (Short,1): User-Defined
ProjCoordTransGeoKey (Short,1): CT_LambertConfConic_2SP
ProjLinearUnitsGeoKey (Short,1): Linear_Meter
ProjStdParallel1GeoKey (Double,1): 38.6666667
ProjStdParallel2GeoKey (Double,1): 33.3333333
ProjFalseEastingGeoKey (Double,1): 0
ProjFalseNorthingGeoKey (Double,1): 0
ProjFalseOriginLongGeoKey (Double,1): -100.583333
ProjFalseOriginLatGeoKey (Double,1): 38
End_Of_Keys.
End_Of_Geotiff.

Projection Method: CT_LambertConfConic_2SP
ProjFalseOriginLatGeoKey: 38.000000 ( 38d 0' 0.00"N)
ProjFalseOriginLongGeoKey: -100.583333 (100d35' 0.00"W)
ProjStdParallel1GeoKey: 38.666667 ( 38d40' 0.00"N)
ProjStdParallel2GeoKey: 33.333333 ( 33d20' 0.00"N)
ProjFalseEastingGeoKey: 0.000000 m
ProjFalseNorthingGeoKey: 0.000000 m
GCS: 4269/NAD83
Datum: 6269/North American Datum 1983
Ellipsoid: 7019/GRS 1980 (6378137.00,6356752.31)
Prime Meridian: 8901/Greenwich (0.000000/ 0d 0' 0.00"E)
Projection Linear Units: 9001/metre (1.000000m)

Corner Coordinates:
Upper Left ( 250233.000,-715515.000)
Lower Left ( 250233.000,-792315.000)
Upper Right ( 352633.000,-715515.000)
Lower Right ( 352633.000,-792315.000)
Center ( 301433.000,-753915.000)

Now, to the obvious problem that you're seeing. I ran the image
through a tiffinfo utility and discovered the problem. Here's what
tiffinfo shows:

TIFF Directory at offset 0x15ff3e
Image Width: 800 Image Length: 600
Bits/Sample: 8
Sample Format: unsigned integer
Compression Scheme: None
Photometric Interpretation: RGB color
Samples/Pixel: 3
Rows/Strip: 10
Planar Configuration: separate image planes
Tag 33550: 128.000000,128.000000,0.000000
.
.

It's that Planar Configuration setting of "separate image planes"
that is confusing Ozi. Ozi wants to see "single image plane". As
Dave already pointed out, you can load and save the image using a
general purpose graphics editing program and that will correct that
situation. You will still need to take care of the projection
problem, one way or another, though.

J.G.

P.S. Here's the upper left coordinate in lat/lon:

N 31Deg 31Min 3.9Sec latitude
W 97Deg 57Min 13.1sec longitude

For the lower lower right, it's:

N 30Deg 47Min 50.2Sec latitude
W 96Deg 54Min 31.8Sec longitude

"John Clonts" writes:

Thanks for the tips. I found that when I use the "raw data" it does work as
you say (http://aviationtoolbox.org/raw_data/...onals/current/). Is
this what you are using?

But I have trouble when I try to use one of Kyler's "processed images" from
https://aviationtoolbox.org/Members/...s/map_explorer
I have the problems that J.G. diagnoses below.

TIFF Directory at offset 0x15ff3e
Image Width: 800 Image Length: 600
Bits/Sample: 8
Sample Format: unsigned integer
Compression Scheme: None
Photometric Interpretation: RGB color
Samples/Pixel: 3
Rows/Strip: 10
Planar Configuration: separate image planes
Tag 33550: 128.000000,128.000000,0.000000
.
.

It's that Planar Configuration setting of "separate image planes"
that is confusing Ozi. Ozi wants to see "single image plane".

Ah ha! That was causing problems for ImageMagick too. I just didn't
realize that's what was doing it.

http://www.remotesensing.org/gdal/frmt_gtiff.html

INTERLEAVE=[BAND,PIXEL]: By default TIFF files with band
interleaving (PLANARCONFIG_SEPARATE in TIFF terminology) are
created. These are slightly more efficient for some purposes,
but some applications only support pixel interleaved TIFF
files. In these cases pass INTERLEAVE=PIXEL to produce pixel
interleaved TIFF files (PLANARCONFIG_CONTIG in TIFF
terminology).

So...I added "INTERLEAVE=PIXEL" and now tiffinfo reports this.
TIFF Directory at offset 0x580a1e
Image Width: 1600 Image Length: 1200
Bits/Sample: 8
Sample Format: unsigned integer
Compression Scheme: None
Photometric Interpretation: RGB color
Samples/Pixel: 3
Rows/Strip: 1
Planar Configuration: single image plane
ImageMagick displays a beautiful image now too.

Does that solve the problem you had?

Thank you for the report.

--kyler

"Kyler Laird" wrote in message
...
"John Clonts" writes:

Thanks for the tips. I found that when I use the "raw data" it does work
as
you say (http://aviationtoolbox.org/raw_data/...onals/current/).
Is
this what you are using?

But I have trouble when I try to use one of Kyler's "processed images"
from
https://aviationtoolbox.org/Members/...s/map_explorer
I have the problems that J.G. diagnoses below.

TIFF Directory at offset 0x15ff3e
Image Width: 800 Image Length: 600
Bits/Sample: 8
Sample Format: unsigned integer
Compression Scheme: None
Photometric Interpretation: RGB color
Samples/Pixel: 3
Rows/Strip: 10
Planar Configuration: separate image planes
Tag 33550: 128.000000,128.000000,0.000000
.
.

It's that Planar Configuration setting of "separate image planes"
that is confusing Ozi. Ozi wants to see "single image plane".

Ah ha! That was causing problems for ImageMagick too. I just didn't
realize that's what was doing it.

http://www.remotesensing.org/gdal/frmt_gtiff.html

INTERLEAVE=[BAND,PIXEL]: By default TIFF files with band
interleaving (PLANARCONFIG_SEPARATE in TIFF terminology) are
created. These are slightly more efficient for some purposes,
but some applications only support pixel interleaved TIFF
files. In these cases pass INTERLEAVE=PIXEL to produce pixel
interleaved TIFF files (PLANARCONFIG_CONTIG in TIFF
terminology).

So...I added "INTERLEAVE=PIXEL" and now tiffinfo reports this.
TIFF Directory at offset 0x580a1e
Image Width: 1600 Image Length: 1200
Bits/Sample: 8
Sample Format: unsigned integer
Compression Scheme: None
Photometric Interpretation: RGB color
Samples/Pixel: 3
Rows/Strip: 1
Planar Configuration: single image plane
ImageMagick displays a beautiful image now too.

Does that solve the problem you had?

Thank you for the report.


Kyler,

Thanks that does solve the image display problem!

The other problem remains however: the georeference information is not read
in successfully by Oziexplorer:

The example which works is e.g. the San Antonio Sectional at
http://aviationtoolbox.org/raw_data/...73%20North.tif
:
Its listgeo info is:
Geotiff_Information:
Version: 1
Key_Revision: 1.0
Tagged_Information:
ModelTiepointTag (2,3):
0 0 0
-364619.149 238513.594 0
ModelPixelScaleTag (1,3):
63.781518 63.781518 0
End_Of_Tags.
Keyed_Information:
GTModelTypeGeoKey (Short,1): ModelTypeProjected
GTRasterTypeGeoKey (Short,1): RasterPixelIsArea
GTCitationGeoKey (Ascii,235): "IMAGINE GeoTIFF Support
Copyright 1991 - 2001 by ERDAS, Inc. All Rights Reserved
@(#)$RCSfile: egtf.c $ $Revision: 1.9.2.4 $ $Date: 2002/01/24 16:43:13Z $
Projection Name = Lambert Conformal Conic
Units = meters
GeoTIFF Units = meters"
GeographicTypeGeoKey (Short,1): GCS_NAD83
ProjectedCSTypeGeoKey (Short,1): User-Defined
PCSCitationGeoKey (Ascii,192): "IMAGINE GeoTIFF Support
Copyright 1991 - 2001 by ERDAS, Inc. All Rights Reserved
@(#)$RCSfile: egtf.c $ $Revision: 1.9.2.4 $ $Date: 2002/01/24 16:43:13Z $
Projection = Lambert Conformal Conic"
ProjectionGeoKey (Short,1): User-Defined
ProjCoordTransGeoKey (Short,1): CT_LambertConfConic_2SP
ProjLinearUnitsGeoKey (Short,1): Linear_Meter
ProjStdParallel1GeoKey (Double,1): 30.6666667
ProjStdParallel2GeoKey (Double,1): 25.3333333
ProjNatOriginLongGeoKey (Double,1): -100
ProjFalseOriginLongGeoKey (Double,1): 0
ProjFalseOriginLatGeoKey (Double,1): 30.125
ProjFalseOriginEastingGeoKey (Double,1): 0
ProjFalseOriginNorthingGeoKey (Double,1): 0
End_Of_Keys.
End_Of_Geotiff.

Projection Method: CT_LambertConfConic_2SP
ProjStdParallel1GeoKey: 30.666667 ( 30d40' 0.00"N)
ProjStdParallel2GeoKey: 25.333333 ( 25d20' 0.00"N)
ProjFalseOriginLatGeoKey: 30.125000 ( 30d 7'30.00"N)
ProjFalseOriginLongGeoKey: -100.000000 (100d 0' 0.00"W)
ProjFalseEastingGeoKey: 0.000000
ProjFalseNorthingGeoKey: 0.000000
GCS: 4269/NAD83
Datum: 6269/North American Datum 1983
Ellipsoid: 7019/GRS 1980 (6378137.00,6356752.31)
Prime Meridian: 8901/Greenwich (0.000000/ 0d 0' 0.00"E)
Projection Linear Units: 9001/metre (1.000000m)

Corner Coordinates:
Upper Left (-364619.149, 238513.594) (103d51'44.46"W, 32d13'23.18"N)
Lower Left (-364619.149, -26434.831) (103d46'31.88"W, 29d50' 7.76"N)
Upper Right ( 343419.482, 238513.594) ( 96d21'43.48"W, 32d13'44.30"N)
Lower Right ( 343419.482, -26434.831) ( 96d26'37.91"W, 29d50'28.46"N)
Center ( -10599.834, 106039.382) (100d 6'39.75"W, 31d 4'53.35"N)


The example that does not work is:
https://aviationtoolbox.org/Members/...ul_Y=-676347.0

And its listgeo info is:
Geotiff_Information:
Version: 1
Key_Revision: 1.0
Tagged_Information:
ModelTiepointTag (2,3):
0 0 0
216057 -676347 0
ModelPixelScaleTag (1,3):
128 128 0
End_Of_Tags.
Keyed_Information:
GTModelTypeGeoKey (Short,1): ModelTypeProjected
GTRasterTypeGeoKey (Short,1): RasterPixelIsArea
GTCitationGeoKey (Ascii,8): "unnamed"
GeographicTypeGeoKey (Short,1): GCS_NAD83
ProjectedCSTypeGeoKey (Short,1): User-Defined
ProjectionGeoKey (Short,1): User-Defined
ProjCoordTransGeoKey (Short,1): CT_LambertConfConic_2SP
ProjLinearUnitsGeoKey (Short,1): Linear_Meter
ProjStdParallel1GeoKey (Double,1): 38.6666667
ProjStdParallel2GeoKey (Double,1): 33.3333333
ProjFalseEastingGeoKey (Double,1): 0
ProjFalseNorthingGeoKey (Double,1): 0
ProjFalseOriginLongGeoKey (Double,1): -100.583333
ProjFalseOriginLatGeoKey (Double,1): 38
End_Of_Keys.
End_Of_Geotiff.

Projection Method: CT_LambertConfConic_2SP
ProjStdParallel1GeoKey: 38.666667 ( 38d40' 0.00"N)
ProjStdParallel2GeoKey: 33.333333 ( 33d20' 0.00"N)
ProjFalseOriginLatGeoKey: 38.000000 ( 38d 0' 0.00"N)
ProjFalseOriginLongGeoKey: -100.583333 (100d35' 0.00"W)
ProjFalseEastingGeoKey: 0.000000
ProjFalseNorthingGeoKey: 0.000000
GCS: 4269/NAD83
Datum: 6269/North American Datum 1983
Ellipsoid: 7019/GRS 1980 (6378137.00,6356752.31)
Prime Meridian: 8901/Greenwich (0.000000/ 0d 0' 0.00"E)
Projection Linear Units: 9001/metre (1.000000m)

Corner Coordinates:
Upper Left ( 216057.000,-676347.000) ( 98d18'10.89"W, 31d52'40.87"N)
Lower Left ( 216057.000,-753147.000) ( 98d19'18.60"W, 31d11'12.79"N)
Upper Right ( 318457.000,-676347.000) ( 97d13'22.77"W, 31d51' 4.80"N)
Lower Right ( 318457.000,-753147.000) ( 97d15' 2.51"W, 31d 9'37.59"N)
Center ( 267257.000,-714747.000) ( 97d46'28.56"W, 31d31'13.34"N)


They both look pretty good to me-- the corner coordinates seem to be there,
etc-- but I don't know anything about all the "false origin" stuff.
Oziexplorer doesn't seem to have trouble with the Lambert projection in the
first example though.

I am copying this to the OziUsers List, maybe J.G. can give some more
assistance?

Thanks!
John Clonts
Temple, Texas
N7NZ

"John Clonts" wrote in message ...
"Kyler Laird" wrote in message
...
"John Clonts" writes:

Thanks for the tips. I found that when I use the "raw data" it does work
as
you say (http://aviationtoolbox.org/raw_data/...onals/current/).
Is
this what you are using?

But I have trouble when I try to use one of Kyler's "processed images"
from
https://aviationtoolbox.org/Members/...s/map_explorer
I have the problems that J.G. diagnoses below.

TIFF Directory at offset 0x15ff3e
Image Width: 800 Image Length: 600
Bits/Sample: 8
Sample Format: unsigned integer
Compression Scheme: None
Photometric Interpretation: RGB color
Samples/Pixel: 3
Rows/Strip: 10
Planar Configuration: separate image planes
Tag 33550: 128.000000,128.000000,0.000000
.
.

It's that Planar Configuration setting of "separate image planes"
that is confusing Ozi. Ozi wants to see "single image plane".

Ah ha! That was causing problems for ImageMagick too. I just didn't
realize that's what was doing it.

http://www.remotesensing.org/gdal/frmt_gtiff.html

INTERLEAVE=[BAND,PIXEL]: By default TIFF files with band
interleaving (PLANARCONFIG_SEPARATE in TIFF terminology) are
created. These are slightly more efficient for some purposes,
but some applications only support pixel interleaved TIFF
files. In these cases pass INTERLEAVE=PIXEL to produce pixel
interleaved TIFF files (PLANARCONFIG_CONTIG in TIFF
terminology).

So...I added "INTERLEAVE=PIXEL" and now tiffinfo reports this.
TIFF Directory at offset 0x580a1e
Image Width: 1600 Image Length: 1200
Bits/Sample: 8
Sample Format: unsigned integer
Compression Scheme: None
Photometric Interpretation: RGB color
Samples/Pixel: 3
Rows/Strip: 1
Planar Configuration: single image plane
ImageMagick displays a beautiful image now too.

Does that solve the problem you had?

Thank you for the report.


Kyler,

Thanks that does solve the image display problem!

The other problem remains however: the georeference information is not read
in successfully by Oziexplorer:

The example which works is e.g. the San Antonio Sectional at
http://aviationtoolbox.org/raw_data/...73%20North.tif
:
Its listgeo info is:
Geotiff_Information:
Version: 1
Key_Revision: 1.0
Tagged_Information:
ModelTiepointTag (2,3):
0 0 0
-364619.149 238513.594 0
ModelPixelScaleTag (1,3):
63.781518 63.781518 0
End_Of_Tags.
Keyed_Information:
GTModelTypeGeoKey (Short,1): ModelTypeProjected
GTRasterTypeGeoKey (Short,1): RasterPixelIsArea
GTCitationGeoKey (Ascii,235): "IMAGINE GeoTIFF Support
Copyright 1991 - 2001 by ERDAS, Inc. All Rights Reserved
@(#)$RCSfile: egtf.c $ $Revision: 1.9.2.4 $ $Date: 2002/01/24 16:43:13Z $
Projection Name = Lambert Conformal Conic
Units = meters
GeoTIFF Units = meters"
GeographicTypeGeoKey (Short,1): GCS_NAD83
ProjectedCSTypeGeoKey (Short,1): User-Defined
PCSCitationGeoKey (Ascii,192): "IMAGINE GeoTIFF Support
Copyright 1991 - 2001 by ERDAS, Inc. All Rights Reserved
@(#)$RCSfile: egtf.c $ $Revision: 1.9.2.4 $ $Date: 2002/01/24 16:43:13Z $
Projection = Lambert Conformal Conic"
ProjectionGeoKey (Short,1): User-Defined
ProjCoordTransGeoKey (Short,1): CT_LambertConfConic_2SP
ProjLinearUnitsGeoKey (Short,1): Linear_Meter
ProjStdParallel1GeoKey (Double,1): 30.6666667
ProjStdParallel2GeoKey (Double,1): 25.3333333
ProjNatOriginLongGeoKey (Double,1): -100
ProjFalseOriginLongGeoKey (Double,1): 0
ProjFalseOriginLatGeoKey (Double,1): 30.125
ProjFalseOriginEastingGeoKey (Double,1): 0
ProjFalseOriginNorthingGeoKey (Double,1): 0
End_Of_Keys.
End_Of_Geotiff.

Projection Method: CT_LambertConfConic_2SP
ProjStdParallel1GeoKey: 30.666667 ( 30d40' 0.00"N)
ProjStdParallel2GeoKey: 25.333333 ( 25d20' 0.00"N)
ProjFalseOriginLatGeoKey: 30.125000 ( 30d 7'30.00"N)
ProjFalseOriginLongGeoKey: -100.000000 (100d 0' 0.00"W)
ProjFalseEastingGeoKey: 0.000000
ProjFalseNorthingGeoKey: 0.000000
GCS: 4269/NAD83
Datum: 6269/North American Datum 1983
Ellipsoid: 7019/GRS 1980 (6378137.00,6356752.31)
Prime Meridian: 8901/Greenwich (0.000000/ 0d 0' 0.00"E)
Projection Linear Units: 9001/metre (1.000000m)

Corner Coordinates:
Upper Left (-364619.149, 238513.594) (103d51'44.46"W, 32d13'23.18"N)
Lower Left (-364619.149, -26434.831) (103d46'31.88"W, 29d50' 7.76"N)
Upper Right ( 343419.482, 238513.594) ( 96d21'43.48"W, 32d13'44.30"N)
Lower Right ( 343419.482, -26434.831) ( 96d26'37.91"W, 29d50'28.46"N)
Center ( -10599.834, 106039.382) (100d 6'39.75"W, 31d 4'53.35"N)


The example that does not work is:
https://aviationtoolbox.org/Members/...ul_Y=-676347.0

And its listgeo info is:
Geotiff_Information:
Version: 1
Key_Revision: 1.0
Tagged_Information:
ModelTiepointTag (2,3):
0 0 0
216057 -676347 0
ModelPixelScaleTag (1,3):
128 128 0
End_Of_Tags.
Keyed_Information:
GTModelTypeGeoKey (Short,1): ModelTypeProjected
GTRasterTypeGeoKey (Short,1): RasterPixelIsArea
GTCitationGeoKey (Ascii,8): "unnamed"
GeographicTypeGeoKey (Short,1): GCS_NAD83
ProjectedCSTypeGeoKey (Short,1): User-Defined
ProjectionGeoKey (Short,1): User-Defined
ProjCoordTransGeoKey (Short,1): CT_LambertConfConic_2SP
ProjLinearUnitsGeoKey (Short,1): Linear_Meter
ProjStdParallel1GeoKey (Double,1): 38.6666667
ProjStdParallel2GeoKey (Double,1): 33.3333333
ProjFalseEastingGeoKey (Double,1): 0
ProjFalseNorthingGeoKey (Double,1): 0
ProjFalseOriginLongGeoKey (Double,1): -100.583333
ProjFalseOriginLatGeoKey (Double,1): 38
End_Of_Keys.
End_Of_Geotiff.

Projection Method: CT_LambertConfConic_2SP
ProjStdParallel1GeoKey: 38.666667 ( 38d40' 0.00"N)
ProjStdParallel2GeoKey: 33.333333 ( 33d20' 0.00"N)
ProjFalseOriginLatGeoKey: 38.000000 ( 38d 0' 0.00"N)
ProjFalseOriginLongGeoKey: -100.583333 (100d35' 0.00"W)
ProjFalseEastingGeoKey: 0.000000
ProjFalseNorthingGeoKey: 0.000000
GCS: 4269/NAD83
Datum: 6269/North American Datum 1983
Ellipsoid: 7019/GRS 1980 (6378137.00,6356752.31)
Prime Meridian: 8901/Greenwich (0.000000/ 0d 0' 0.00"E)
Projection Linear Units: 9001/metre (1.000000m)

Corner Coordinates:
Upper Left ( 216057.000,-676347.000) ( 98d18'10.89"W, 31d52'40.87"N)
Lower Left ( 216057.000,-753147.000) ( 98d19'18.60"W, 31d11'12.79"N)
Upper Right ( 318457.000,-676347.000) ( 97d13'22.77"W, 31d51' 4.80"N)
Lower Right ( 318457.000,-753147.000) ( 97d15' 2.51"W, 31d 9'37.59"N)
Center ( 267257.000,-714747.000) ( 97d46'28.56"W, 31d31'13.34"N)


They both look pretty good to me-- the corner coordinates seem to be there,
etc-- but I don't know anything about all the "false origin" stuff.
Oziexplorer doesn't seem to have trouble with the Lambert projection in the
first example though.

I am copying this to the OziUsers List, maybe J.G. can give some more
assistance?


Kyler,

This is the input I got from J.G. on the OziUsers list, regarding the
above:

begin quote
I took a look at the goetiff tags for the two images and I think I
see the problem. The full image is specifying a key:

ProjNatOriginLongGeoKey (Double,1): -100

While the smaller image does not even have that key. Somehow, the
smaller image is using the tag:

ProjFalseOriginLongGeoKey (Double,1): -100.583333

These can't both be right. I'd say the full image is the right one,
since it loads fine in not just Ozi, but other programs too, while
the smaller image does not work in other programs. I'm pretty
certain that the ProjNatOriginLongGeoKey is only supposed to be used
in cases where the prime meridian is not the familiar 0 degrees
longitude value. Technically, the math may work, to subvert the
function of that tag and then specify the ProjFalseOriginLongGeoKey
as 0.0, but it's highly irregular. Listgeo is able to deal with it,
by translating the natorigin key to it's equivalent falseorigin key,
but programs generating geotiff files should not rely on geotiff
readers to do this.

All that said, you can fix these keys. If you redirect the output of
the listgeo program to a file, you can edit that file with any
ordinary text editor and reinstall it into the geotiff file, using
the geotifcp program, which is part of the zip file I referred to
previously.

J.G.
end quote

By full image he means the San Antonio sectional ("raw"), and by
"smaller image" he means the one provided by your map_explorer link...

Hope that helps,
John

"John Clonts" wrote in message
om...

Kyler,

This is the input I got from J.G. on the OziUsers list, regarding the
above:

begin quote
I took a look at the goetiff tags for the two images and I think I
see the problem. The full image is specifying a key:

ProjNatOriginLongGeoKey (Double,1): -100

While the smaller image does not even have that key. Somehow, the
smaller image is using the tag:

ProjFalseOriginLongGeoKey (Double,1): -100.583333

These can't both be right. I'd say the full image is the right one,
since it loads fine in not just Ozi, but other programs too, while
the smaller image does not work in other programs. I'm pretty
certain that the ProjNatOriginLongGeoKey is only supposed to be used
in cases where the prime meridian is not the familiar 0 degrees
longitude value. Technically, the math may work, to subvert the
function of that tag and then specify the ProjFalseOriginLongGeoKey
as 0.0, but it's highly irregular. Listgeo is able to deal with it,
by translating the natorigin key to it's equivalent falseorigin key,
but programs generating geotiff files should not rely on geotiff
readers to do this.

All that said, you can fix these keys. If you redirect the output of
the listgeo program to a file, you can edit that file with any
ordinary text editor and reinstall it into the geotiff file, using
the geotifcp program, which is part of the zip file I referred to
previously.

J.G.
end quote

Hello Kyler,

FYI, I patched the tags in my test file (from
https://aviationtoolbox.org/Members/...ul_Y=-676347.0)
with geotifcp per J.G.'s instructions, and Oziexplorer is happy with that
image now. Do you know if changing your generation code would be
appropriate, and/or cause other problems with other software?

Cheers,
John

"John Clonts" writes:

FYI, I patched the tags in my test file (from
https://aviationtoolbox.org/Members/...ul_Y=-676347.0)
with geotifcp per J.G.'s instructions, and Oziexplorer is happy with that
image now. Do you know if changing your generation code would be
appropriate, and/or cause other problems with other software?

It's appropriate and I want to do it. If it causes any problems, I'll
work through them. I want these things to be correct.

Yesterday I distilled the code to a few lines that demonstrate the
problem and sent a report to the GDAL developer mailing list.
http://remotesensing.org/mailman/listinfo/gdal-dev/
It hasn't appeared in the archives yet.

I welcome more reports to the list. My trivial example is below.

Thank you.

--kyler

================================================== ========================
#!/usr/bin/env python

import gdal

a = gdal.Open('a.tif')

b = gdal.GetDriverByName('GTiff').Create(
'b.tif',
a.RasterXSize, a.RasterYSize,
3, gdal.GDT_Byte,
[ 'TILED=YES' ]
)

b.SetProjection(a.GetProjection())
b.SetGeoTransform(a.GetGeoTransform())