DTED file format

GRASS GRASS user
1

From: ludwig@cs.washington.edu (Jim Ludwig)
Subject: DTED file format

I am very new to GRASS, and my first project has been to read in a
DTED file and do some stuff with it (which is irrelevant).

My problem is that I can't seem to be able to read in the DTED file.
I've tried a variety of things, and I believe my problem boils down to
this: I don't know where the header of the file ends and where the
data of the file begins.

Is anyone out there familiar with DTED files? The manual seems to be
vague... Knowing what to trim would be most helpful.

Are you reading from a tape, or from a file? I don't think m.dted.extract
will read from a file unless the blocking factor of 4096 is maintained. I'm
developing code to read DTED files that are unblocked. I have modified
m.dted.examine so that it will read the header of an unblocked file.

What results do you get using m.dted.examine as is in GRASS 4.1? And does
your format follow the pre-1987 header format? Have you read 'GRASS 4.0
Tutorial: DTED and DEM Elevation Data Extraction?'

greg

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Thanks,
  jim

2

From: greg@towhee.cor2.epa.gov (Greg Koerper)

Are you reading from a tape, or from a file?

I'm reading from a file.

I don't think m.dted.extract will read from a file unless the blocking
factor of 4096 is maintained.

I had assumed that, because the file had already been created on disk,
it didn't need to be "extract"ed. Was this a false assumption? The
manual indicates that m.dted.extract is used to extract the file from
the tape. What is a blocking factor?

What results do you get using m.dted.examine as is in GRASS 4.1?

I am using GRASS 4.0 and I have discovered that m.dted.examine is not
in my set of GRASS commands (I just sent mail to my sysadmin regarding
that). On the other hand, like with m.dted.extract, the manual states
that the "examine" command is to be used in conjunction with a tape...

And does your format follow the pre-1987 header format?

I really don't know. I have been using GRASS for less than a week.

Have you read 'GRASS 4.0 Tutorial: DTED and DEM Elevation Data
Extraction?'

No, but I would very much be interested in knowing where to find it...

Thanks,
  jim

Original message:

> I am very new to GRASS, and my first project has been to read in a
> DTED file and do some stuff with it (which is irrelevant).
>
> My problem is that I can't seem to be able to read in the DTED file.
> I've tried a variety of things, and I believe my problem boils down to
> this: I don't know where the header of the file ends and where the
> data of the file begins.
>
> Is anyone out there familiar with DTED files? The manual seems to be
> vague... Knowing what to trim would be most helpful.
>