Updating the TAOS Topography/Bathymetry Database

This material was developed for a TAOS/L user workshop at the Caribbean Institute for Meteorology and Hydrology, July 1999.

Note: File names, directory names, and file formats will be in bold. In addition, quotation marks will be used the first time a file is mentioned in the text. Commands to be executed inside a software package will be presented as a sequence of menu names, such as "File/Import/Vector."

No translators are necessary to move files back and forth between the two softwares.. Both the vector file that displays in TAOS and the raster file underlying the model’s calculations are in IDRISI format. You will, however, need documentation files. For raster files, the header information may already be in "area.dat". Taos only reads the top two or three lines of area.dat, so it does no harm to include the information for Idrisi below that. Example:

-90.0000 -59.0000 9.0000 24.0000 3720 1800
1.000000
35
file title : Window from topo3000 c: 3600 r: 1080 to c: 7319 r: 2879
data type : real
file type : binary
columns : 3720
rows : 1800
ref. system : lat/long
ref. units : deg
unit dist. : 1.0000000
min. X : -90.0000000
max. X : -59.0000000
min. Y : 9.0000000
max. Y : 24.0000000
pos'n error : unknown
resolution : unknown
min. value : -8103.0000000
max. value : 5421.0000000
value units : m
value error : unknown
flag value : none
flag def'n : none
legend cats : 0

The top three lines are to help TAOS read the file called "Topo.bin". To adapt this for IDRISI, delete down to but not including the line that starts with "file title." Save the result as text, with an extension ".DOC", for instance "Topo.doc".

The example above is for a raster "topo.bin" arranged in 3720 columns and 1800 rows. The reference systen is degrees of latitude and longitude, extending from 90 degrees west to 59 degrees west, and from 9 degrees north to 24 degrees north: the Caribbean Basin. The deepest trench in the ocean is 8103 meters deep, and the highest mountain is 5421 meters high.

Now you have a file pair *.doc and *.bin. When you start IDRISI, you can tell the system to treat files with extension .bin as images, but you are better off just changing topo.bin to topo.img. That way, you can work with topo creating new images through the many functions IDRISI offers.

One interesting trick: The various topo.bin files are 4-byte real numbers (IEEE floating-point ""ntel""format) but as it happens, they all consist of whole numbers. So, in IDRISI, you can use the command Reformat/Convert to change the map to 2-byte integer numbers. Your new file will only be half the size.

IDRISI also uses file pairs for vectors. The file "carib.vec" should have an accompanying file *.dvc somewhere on the directory. It will look something like this:

file title : Caribbean basin, based on 3000 rows for 30 a-s topo.bin
id type : integer
file type : ascii
object type : line
ref. system : latlong
ref. units : deg
unit dist. : 1
min. X : -90
max. X : -59
min. Y : 9
max. Y : 24
pos'n error : unknown
resolution : unknown

In fact, there may be more than one .dvc file, with different first names. If you get confused which goes with which, try opening the *.vec file and see if it starts with a bounding rectangle like this:

1.0000000 5
-90.0000000 24.00000
-59.0000000 24.00000
-59.0000000 9.00000
-90.0000000 9.00000
-90.0000000 24.00000
1.0000000 79
-70.0749969 12.6332912
-70.0500031 12.6332912
-70.0500031 12.6249943
-70.0417023 12.6249943
-70.0417023 12.6166973
-70.0333023 12.6166973
-70.0333023 12.6082993
. . . . . . . (and so on . . . )

The top row says that it will be followed by a line with five nodes. The next five rows give the beginning, three corners, and the end of a line which traces a rectangle. (right after that, it starts a new line which will go on for 79 nodes, and so forth to the end of the file.)

These will be the extents of the vector file. You can match this this to the .dvc files you have, or you can use File/Document in IDRISI to create a new .dvc file. The reference system will be latitudes and longitudes, as with the raster set.

To bring improved files back into TAOS, just get them to the right directory, make sure that the vector file you want to see is called "carib.vec" and that the raster file is "topo.bin". The vector file should be in ASCII, not binary, and the raster file should be in real numbers, binary format.