Global AEZ CDrom Image files
============================

The downloadable zip files *.zip comprise all the plates from the
Global AEZ Cdrom in a 1 or 2 byte binary image format.
The images can be imported into any GIS software 
(e.g. Arc/Info,Idrisi,Erdas,etc.).

For each image a header file *.hdr, a world file *.blw and an
IDRISI32 documentation *.rdc file is given. The former two are 
required to import the *.bil images into Arc/Info via the 
"imagegrid" command. 

The *.rdc file is required for use in IDRISI32, together with
the included *.rst files.
In some cases, the *.rdc files are also required by Arc/Info users
to identify the legend of a raster image.

Furthermore, for each plate a *.bmp and a *emf file is available. 
They can be viewed in suitable graphics software (e.g. Microsoft Paint,
CorelDraw, etc. on the PC or XV, ghostview ... under Unix). 

All images:
*) cover the whole globe
*) are in geographic projection, i.e. in longitude, latitude
*) the corner point of the upper left corner is at:
   -180 x-coord and +90 y-coord.
*) use the INTEL byte order
*) store integers

There are four different image sizes:

1) 
cell size: 0.5 degree
360 rows, 720 columns
1 byte integer
*.bil file = 259200 bytes

2)
cell size: 0.5 degree
360 rows, 720 columns
2 byte integer
*.bil file = 518400 bytes

3)
cell size: 5 arc-minute
2160 rows, 4320 columns
1 byte integer
*.bil file = 9331200 bytes

4)
cell size: 5 arc-minute
2160 rows, 4320 columns
2 byte integer
Size of *.bil file is 18662400 bytes

Remarks for Arc/Info users:
==========================
Negative values in the images (such as -9999 for nodata) are 
imported into Arc/Info as positve values by adding 65536.
For example in plate01, the value 55537 should be changed to 
-9999 for nodata (55537 - 65536 = -9999). The "setnull" command
may be used to introduce nodata.
In plate58a and plate58b also negative values occur beside the
nodata value. The commands to import e.g. plate58a are listed below:

Grid: arc imagegrid plate58a.bil tmp_plate58a
Grid: pl58a = con (tmp_plate58a > 10000, tmp_plate58a - 65536, tmp_plate58a)
Grid: kill tmp_plate58a
 



