#28 ADRG: corrupted image data for large selected region

[Anonymous]

My contact info:

Dan DeJohn
Digicomp Research
607-273-5900 x23
dejohn@digicomp.com
djdejohn@yahoo.com

I am using OGDI 3.1.1 to read an ADRG dataset from which I
create an image. When I select a region that is "too
wide", OGDI
corrupts the data returned in subsequent image lines. This
happens with every ADRG dataset I have tried. I'm using
ADRG
aeronautical charts from NIMA.

I've tried to collect some specific data to show when this
happens. Any ideas what's wrong?

In the first example, I'm using the NIMA Jet Nav dataset,
JNCXX044. I'm selecting layer zero of the dataset, and
scaling
the image onto a 500x500 pixel image. First, I select a
region
with bounds:

N= 33.8358 S= 30.6716 E=-84.7490 W=-91.2510

This region is 6.502078644667 degrees wide. The "native"
resolution of the layer (according to the
ecs_LayerCapabilities)
is 0.001904348000 degrees, so the selected region is
3414.3332
resolution cells wide.

Here is the image, and it looks fine.

IMAGE1.jpg

When I change the selected region to

N= 33.8360 S= 30.6709 E=-84.7480 W=-91.2520

which is 6.503980205630 degrees wide, or 3415.3318
resolution
cells wide, OGDI returns corrupted data as shown in
this image:

IMAGE2.jpg

The problem doesn't depend on scaling. As long as I
select a
region fewer than 3415 cells wide, OGDI will scale it
onto any
size rectangle and the image will be clear. If the
region is
greater than 3415 cells wide, the image will be corrupted.

The problem also doesn't depend on geographic area. I can
select any region that intersects the layer and the
image is OK
as long as the region is less than 3415 resolution
cells wide.

The critical region size (in number of resolution
cells) above
which the data is corrupted varies from layer to layer and
between datasets. When I display layer one of the same
dataset,
the image is OK only if I select a region smaller than 4080
resolution cells wide:

(The text before the image is diagnostic output of my
test.)

Doing layer 1
Layer is nm=jnus0102.img titl=<null> srs=+proj=longlat
bnds?=1
lN= 49.50107778 lS= 31.99848056 lE=-84.49851944
lW=-104.00073889
sN= 49.50107778 sS= 31.99848056 sE=-84.49851944
sW=-104.00073889 NSres= 0.001775832000 EWres=
0.002308501000
qes?=0 pfx=<null> sfx=<null> fmt=<null> descr=<null>
Region width is 9.418463303759 degrees wide, or
4079.9044 resolution cells wide
Selecting region
N= 37.9237 S= 32.0049 E=-84.5152 W=-92.7092
NSres=0.015700 EWres=0.018837

IMAGE3.jpg

Doing layer 1
AOI is N= 37.9245 S= 30.0730 E=-83.2898 W=-92.7102
NSres=0.015703 EWres=0.018841
Layer is nm=jnus0102.img titl=<null> srs=+proj=longlat
bnds?=1
lN= 49.50107778 lS= 31.99848056 lE=-84.49851944
lW=-104.00073889
sN= 49.50107778 sS= 31.99848056 sE=-84.49851944
sW=-104.00073889 NSres= 0.001775832000 EWres=
0.002308501000
qes?=0 pfx=<null> sfx=<null> fmt=<null> descr=<null>
Region width is 9.420361619544 degrees wide, or
4080.7267 resolution cells wide
Selecting region
N= 37.9245 S= 32.0045 E=-84.5145 W=-92.7102
NSres=0.015703 EWres=0.018841

IMAGE4.jpg

Here's a different dataset, ONCXXH24, in which the critical
region size is 3448 cells. You can see in the corrupted
image
that some of the data is being repeated.

Doing layer 0
AOI is N= 29.4636 S= 26.5361 E=-86.7510 W=-90.0490
NSres=0.005855 EWres=0.006596
Layer is nm=onus0101.img titl=<null> srs=+proj=longlat
bnds?=1
lN= 32.00027778 lS= 23.99975833 lE=-84.99924167
lW=-97.00008611
sN= 32.00027778 sS= 23.99975833 sE=-84.99924167
sW=-97.00008611 NSres= 0.000880339000 EWres=
0.000956700000
qes?=0 pfx=<null> sfx=<null> fmt=<null> descr=<null>
Region width is 3.298029638973 degrees wide, or
3447.2976 resolution cells wide
Selecting region
N= 29.4636 S= 26.5361 E=-86.7510 W=-90.0490
NSres=0.005855 EWres=0.006596

IMAGE5.jpg

Doing layer 0
AOI is N= 29.4644 S= 26.5353 E=-86.7500 W=-90.0500
NSres=0.005858 EWres=0.006600
Layer is nm=onus0101.img titl=<null> srs=+proj=longlat
bnds?=1
lN= 32.00027778 lS= 23.99975833 lE=-84.99924167
lW=-97.00008611
sN= 32.00027778 sS= 23.99975833 sE=-84.99924167
sW=-97.00008611 NSres= 0.000880339000 EWres=
0.000956700000
qes?=0 pfx=<null> sfx=<null> fmt=<null> descr=<null>
Region width is 3.299933465188 degrees wide, or
3449.2876 resolution cells wide
Selecting region
N= 29.4644 S= 26.5353 E=-86.7500 W=-90.0500
NSres=0.005858 EWres=0.006600

IMAGE6.jpg