Data format for DETEC-1 and DETEC-2
Introduction
If you look at the data we have acquired with the DETEC-1 and DETEC-2
prototypes,
you will see two kinds of files. The first category, with a filename
beginning
with S, contains the raw traces acquired directly from the GPR
without
any modification or treatment. The position of each trace is also
stored
in these files. As the acquisitions are not performed on a regular
grid,
this type of data can be difficult to process. For this reason we have
also stored the same data interpolated on a fixed grid (usually 1cm by
1cm). These files have a filename beginning with I.
We have difined these two new file types, because the seg2
format
used for our previous acquisitions is not suited for the acquision of a
2D area.
File names
We are working with MS-DOS filenames, i.e. a miximum of 8 characters
and
a 3 character extension. To clearly identify every scan, we encode the
current date and add the number of the scan, starting every morning at
zero.
This leads to the following filename format : xttyyzzz.nnn
where :
x : type of file
S for sequential raw data
I for interpolated data cube
tt : team identification
every team is identified by a two digit number
yy : year of scan
nnn : number of the scan
starting at 0 every morning
32 bit
file Identifier
The information coded in the filename is also stored as a 32 bit value
in the files. With the following convention :
identifier = 8 * ttyyzzznnn + i
where i is 0 for a type 'S' file and 1 for a type 'I' file.
Type 'S'
file format
Header
| 16 bit field |
Comment |
| Format identifier |
"SD" |
| Identifier low |
|
| Identifier high |
|
| Format version |
8 bit version, 8 bit release |
| Samples per trace |
|
| Sampling interval |
ps |
Data
The header is directly followed by the first acquired trace, consisting
of n samples (16 bit each) and the coordinates of the trace (two 16 bit
values in millimeter).
A Matlab
routine is available to read this type of file.
Type 'I'
file format
Header
| 16 bit field |
Comment |
| Format identifier |
"ID" |
| Identifier low |
|
| Identifier high |
|
| Format version |
8 bit version, 8 bit release |
| Number of points in X dir |
|
| Number of points in Y dir |
|
| Samples per trace |
|
| Resolution in X |
mm |
| Resolution in Y |
mm |
| Sampling interval |
ps |
Data
The header is directly followed by n samples (16 bit each) of the trace
at position (0,0) in the cube. The following traces comes with the X
position
incrementing first.
A Matlab
routine is available to read this type of file (you will need
Matlab
5 to use it, as it returns a 3D matrix).
http://diwww.epfl.ch/lami/detec/detec2format.html
Created by BG / Last
modified
by BG 17.10.1997
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hard | GPR soft | DeTeC
| EPFL
