MAKGRD
Latest: MAKGRD v2.0 (20APR18) [Fortran] [Python]
20AUG25

Contents

Introduction

Part of the RFM handling of Irregular Spectral Grids (.grd files)

MAKGRD is a Fortran90 program to convert a user-supplied list of spectral axis points into the RFM .grd file format.

The same operation can be achieved using the Python class rfm_grd_class.py

General Comments

  1. A .grd file contains a series of '1's and '0's on a spectral fine grid (encoded in groups of 4 as hexadecimal characters): '1' indicates a fine grid point which is to be used for the spectral and radiative transfer calculations when the RFM GRD Flag is enabled (otherwise the RFM performs calculations at all fine grid points).
  2. Generating such a file is non-trivial (the format comes from the RFM's origins as a tool to support MIPAS processing), so this program has been written to to convert a simple list of spectral points in either wavenumber [cm-1] or frequency [GHz] units.
  3. The spectral points have to be in monotonically increasing order, and must all be integer multiples of some fundamental fine grid spacing, which the user also specifies.
  4. The default option is to produce an output .grd file which exactly matches the spectral range of the user-supplied points, but the user has the option of modifying this range (any extension being filled with '0' values).

Installing MAKGRD

Download the source code: [makgrd.f90] or [rfm_grd_class.py]

If using the Fortran code, compile with any generic Fortran compiler, eg

gfortran makgrd.f90 -o makgrd
which will create an executable file makgrd

Running MAKGRD

To run the Fortran program, type makgrd and respond to the prompts (this is the Fortran version but the Python version is essentially the same).

A typical run might be (user responses, <CR> = Return)

makgrd R-MAKGRD: Running MAKGRD v2.0 Fundamental resolution: 0.0005 File containing spectral points: points.txt Output spectral range (= 800.0000: 800.8000 [cm-1]): <CR> Output .grd file: points.grd R-MAKGRD: Successful completion

The program should run almost instantaneously.

For the Python version, if no change in spectral range is required, it can be performed with a single call of the make method within the Rfm_Grd class:

from rfm_grd_class import Rfm_Grd grd = Rfm_Grd() # instantiate grd.make ( 'points.txt', 0.0005, 'points.grd' )

Alternatively, and if a change in spectral range is required, use the wnolim and write methods:

from rfm_grd_class import Rfm_Grd grd = Rfm_Grd() # instantiate grd.make ( 'points.txt', 0.0005 ) grd.wnolim() # no arguments -> just report current range grd.wnolim ( 800.1,800.2 ) # alter range grd.write ( 'points.grd' ) # create .grd file

This creates terminal output

Current Range: 800.0000 800.8000 [cm-1] New Range: 800.1000 800.2000 [cm-1] Creating file: points.grd

Notes

  1. It is assumed that the user-supplied set of irregular grid points represent a sub-sampling of some underlying regular grid (here, 0.0005)
  2. User's file points.txt contains the list of spectral points (see List file, below).
  3. The user has the option of setting the output file to maintain the original spectral range of the supplied grid points (as here), or of adjusting the range. If extended, the output file will simply be padded with '0's.

List file

The user supplies a set of spectral points in a file with the following format:
File Structure for List File
HEADER Optional records
NSPC Single record
SPC(1) SPC(2) ...
... SPC(NSPC)
[eof]
Where the fields are defined as follows
FieldTypeDescriptionUnits Range
HEADER C80 Comment record
NSPC I No.spectral points ≥1 or ≤1
SPC D Spectral point value cm-1 or GHz
Type: I=Integer; D=Double Precision; Cn=character string, length n.

Notes

  1. If the first character of the first record is '!' then this is interpreted as a comment record and passed to the output file as the initital CONFIG record (see .grd file format). If there is no initial comment record, the name of the list file is written to the CONFIG record.

  2. The first non-comment record should contain just an integer indicating the number of spectral points to follow. A negative value of NSPC indicates that the points are in [GHz], while a positive value indicates [cm-1].

  3. Then follows the set of spectral points in monotonically increasing order, read free-format.

Examples

The following is an example of a list of points, actually just sampling a 0.0005 cm-1 grid at 0.004 cm-1 spacing.

! test data 201 800.00000 800.00400 800.00800 800.01200 800.01600 800.02000 800.02400 800.02800 800.03200 800.03600 800.04000 800.04400 800.04800 800.05200 800.05600 ... 800.78000 800.78400 800.78800 800.79200 800.79600 800.80000

This file generates the following output .grd file

! test data ! Created by program makgrd.f90 v2.0 lin 1601 201 800.0000 0.0005 0.0 120.0 80808080808080808080808080808080808080808080808080 80808080808080808080808080808080808080808080808080 80808080808080808080808080808080808080808080808080 80808080808080808080808080808080808080808080808080 80808080808080808080808080808080808080808080808080 80808080808080808080808080808080808080808080808080 80808080808080808080808080808080808080808080808080 80808080808080808080808080808080808080808080808080 8

Error Messages

Fatal error messages may occur if there are I/O errors on the input or output files, if the spectral points are not multiples of the fundamental grid, or if the user specifies a modified output range which is inconsistent with the input data.

Version History

v2.00 (20AUG25)
Change Python code to be a method of the Rfm_Grd class
v2.00 (06FEB25)
Added Python version
v2.00 (20APR18)
Recoded in FORTRAN 90 but, from the user's viewpoint, unchanged.
v1.00 (23JUL15)
Original code (F77)