GCOM-C SGLIRSP Path Detection in L2 Tile
Tool

User’s Manual
Version 1.0

Nov. 2022
JAXA
GCOM-C projectUser’s Manual
Change Records (1/1)
Ver.

Rev.

Date

1.0-Nov. 2022

Page

Contents
First edition

Contents
1． Introduction ........................................................................................ 1
2． System Requirements ....................................................................... 1
3． Input Products / Available Datasets ................................................. 1
4． Operation ............................................................................................ 2
5． Output Files ........................................................................................ 35.1 File naming ..............................................................................................................3

6． License information ........................................................................... 4
7． Appendix ............................................................................................ 5
7.1 The detection of the number of RSP-path ............................................................5
7.2 GeoTIFF conversion with the external tool ..........................................................7

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1． Introduction
This user’s manual explains how to use the tool for “RSP Path Detection in L2 Tile ofGCOM-C/SGLI HDF5 products”. This tool detects the number of RSP-path for rasterdata in the L2-tiles on a daily basis (01D) based on the observing time and attaches itto the original filename. If the tile includes multiple RSP paths, the tool separates thetile for each of the paths and outputs their corresponding multiple HDF5 files. The typeof tool is CUI (Character User Interface) so that users can install it into their system or
scripts for mass processing.

2． System Requirements
Hardware Requirements
・CPUIntel Xeon/Core-i7 or higher・Memory1GByte or higher.

Operating Systems
・LinuxKernel 2.6 or higher (64bit)
The operation test has been done on RHEL7/CentOS7.

・Windows

Windows 10 (64bit)

3． Input Products / Available Datasets
Available input SGLI HDF5 products for this tool are L2-tiles on a daily basis (01D) asfollows:
LTOA, RSRF, VGI, LAI, AGB, LST, CLFG, CLPR, ARNP, ARPL, SICE, SIPR
The tool uses the following dataset, which indicates the observing time of all rasterdata in the tile, for detecting the number of RSP-path.
Geometry_data/Obs_time
The following products do not include the above dataset; therefore, the tool needs anadditional input of the LTOA or RSRF product that has the same Granule ID as areference.
VGI, LAI, AGB, SICE, SIPR

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If the target tile has the resolution of 250 m (Q), the reference LTOA/RSRF should bethe same resolution.
If the tile includes multiple RSP paths, the tool separates the data for each of the paths.
The target data for the separation are all raster datasets, which the size is 4800 x 4800
or 1200 x 1200, in the HDF Group of the Image_data and the Geometry_data.
The details of the datasets in the L2-tile products can be found at:https://suzaku.eorc.jaxa.jp/GCOM_C/data/product_std.html

4． Operation
Put the downloaded .exe file at any folder/directory in your file system. No installationis required. Run the .exe file at a command prompt (a terminal for Linux).
> SGLI_t2p_linux(win).exe [hdf_filename(*.h5)] [OPTIONS]OPTIONS:
Option&Parameter

Description
Set the reference LTOA or RSRF product(*.h5) at HDF_FILE.
The Granule-ID should be the same as the target L2-tile-r HDF_FILE

product. This is mandatory for target L2-tile productsthat has no Obs_time dataset in the Geometry_data group(i.e., VGI, LAI, AGB, SICE, SIPR).

-o OUTPUTDIR

Set a directory for output files to OUTPUTDIR. If this was not
specified, the tool outputs files to a current directory.

-hPrint a usage message and exit.

-v

Print version and license information and exit.

Examples:
1) Process L2/LTOAQ product, the output directory is “./output”> SGLI_t2p_linux.exe [L2/LTOAQ].h5 -o ./output
2) Process L2/LAI> SGLI_t2p_linux.exe [L2/LAI_Q].h5 -r [L2/LTOAQ]

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5． Output FilesThe output file is the HDF5 with the number of RSP path attached in the filename. If
the tile includes multiple RSP paths, the multiple files for each of the paths are
separately output.

5.1

File naming

The rules of naming for output files are as follows:
GID_PPP.h5
where,GID is the Granule ID of an input HDF product,
PPP is the number of the RSP paths (001~485).
Example:GC1SG1_20220627D01D_T0427_L2SG_LTOAQ_2012_039.h5
GC1SG1_20220627D01D_T0427_L2SG_LTOAQ_2012_073.h5

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6． License information
The tool includes the open-source libraries for the file interface of the HDF5. The
license information is as follows:
Copyright Notice for HDF5 (Hierarchical Data Format 5) Software Library========================================================HDF5 (Hierarchical Data Format 5) Software Library and Utilities
Copyright (c) 2006-2018, The HDF Group.
NCSA HDF5 (Hierarchical Data Format 5) Software Library and Utilities
Copyright (c) 1998-2006, The Board of Trustees of the University of Illinois.
All rights reserved.
https://www.hdfgroup.org/licenses (accessed Nov. 1, 2022)

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7． Appendix
7.1

The detection of the number of RSP-path

This section briefly explains the algorithm for the detection of the number of RSP-path.
The number of RSP-path is detected from the dataset of Geometry_data/Obs_time,
which gives the time from the epoch of UT00:00 at the date of the Granule ID, by usingthe nominal parameters of the satellite orbit.
Let the t d be the time in the above dataset and t d0 is the epoch time of the Granule ID,
the number of RSP-path P is given as the following formula,𝑃𝑃 = 𝑚𝑚𝑚𝑚𝑚𝑚 �𝑃𝑃0 + 𝑖𝑖𝑖𝑖𝑖𝑖 �𝑡𝑡𝑑𝑑 + (𝑡𝑡𝑑𝑑0 − 𝑡𝑡𝑅𝑅𝑅𝑅𝑅𝑅 )� ∙ 𝑁𝑁 − 1, 𝑋𝑋� + 1
𝑡𝑡𝑂𝑂𝑂𝑂𝑂𝑂

where, mod(a,b) is the remainder of a division of a by b, int() is a conversion to aninteger with rounding-down, P 0 is the reference number of RSP-path, t REF is thepassing time of the ascending node of P 0 , N is the recurrent period, X is the total
number of RSP-paths, and t ORB is the period of orbit cycle. The setting of these nominal
orbital parameters are as follows:

P 0 = 196

t REF = 2018-01-16 07:57:14 (UT)N = 34

X = 485t ORB = N/X*86400

The actual satellite orbit has errors in the passing time of the ascending node from thenominal, hence, it may cause a miss-detection of the RSP-path number in ascending
tiles around the equator. To detect and correct the miss-detection, a relative timedifference t d - AN between the observation and the ascending node is calculated as𝑡𝑡𝑑𝑑−𝐴𝐴𝐴𝐴 = 𝑡𝑡𝑑𝑑 + 𝑡𝑡𝑑𝑑0 − 𝑡𝑡𝐴𝐴𝐴𝐴
where, t AN is the nominal passing time of the ascending node and is calculated as5

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𝑡𝑡𝐴𝐴𝐴𝐴 = 𝑖𝑖𝑖𝑖𝑖𝑖 �𝑡𝑡𝑑𝑑 + (𝑡𝑡𝑑𝑑0 − 𝑡𝑡𝑅𝑅𝑅𝑅𝑅𝑅 )� ∙ 𝑡𝑡𝑂𝑂𝑂𝑂𝑂𝑂 + 𝑡𝑡𝑅𝑅𝑅𝑅𝑅𝑅
𝑡𝑡𝑂𝑂𝑂𝑂𝑂𝑂

The t d-AN is used to check the miss-detection, where it implies the relative position fromthe equator, while the tile ID indicates the hemisphere of north or south. For tiles of thenorthern hemisphere in ascending tiles (i.e., tile ID = T00**~T08**), if the t d-AN is greaterthan a threshold T N , the number of RSP-path is detected being shifted backward andis added by N. For tiles of the southern hemisphere (i.e., tile ID = T09**~T17**), if thet d-AN is less than a threshold T S , the number of RSP-path is detected being shifted
forward and is subtracted by N. Both of T N and T S are set to 3000 seconds as approx.
the half of the period of orbit cycle.
Note that this algorithm does not support the “RSP shifts” that temporarily occurredbecause of non-routine orbital maneuvers. In that period, the number of RSP-path has
the error of +1. The details of the “RSP shift” can be found at:https://shikisai.jaxa.jp/docs/event_information.pdf
See records that the Comments = “RSP is 1 more than nominal” at Table 1.

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7.2

GeoTIFF conversion with the external tool

The output HDF5 files of this tool can be converted into GeoTIFF format files with theexternal tool "Map projection & GeoTIFF conversion Tool."
A sample shell script in the Bash at Linux OS that implements the procedure is asfollows:#-----------------------------------------------------------#!/bin/bash#set the input file and output directory
file="GC1SG1_20220627D01D_T0427_L2SG_LTOAQ_2012.h5"
outdir="./output"#run the "RSP Path Detection in L2 Tile Tool"/(exedir)/SGLI_t2p_linux.exe $file -o $outdir#omit the extension of the input filename
file1=`basename $file .h5`
#run the "Map projection & GeoTIFF conversion Tool"#for all output files from the "RSP Path Detection in L2 Tile Tool"for f in ${outdir}/${file1}_???.h5; do/(exedir)/SGLI_geo_map_linux.exe $f -d "Image_data/Lt_VN01" -o $outdir
done#-----------------------------------------------------------For Windows OS, the procedure can be implemented in the standard scripting
language such as the PowerShell.

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