GMS-5 (Geostationary Meteorological Satellite)
Information updated on Fri Jul 13 18:39:39 2007
General Data Description
GMS-5 satellite images are taken over the Tropical Western Pacific (TWP) region and over each of the TWP sites. The raw data are downlinked to the SeaSpace Corp. receiving station at the University of Hawaii.
The GMS 5 satellite characteristics
GMS-5 was launched in March 1995 into a geostationary orbit above 0o
N, 140oE. It carries a Visible and Infrared Spin Scan Radiometer
(VISSR) with four channels, one in the visible part of the spectrum and three
in the infrared. The ground resolution at the subsatellite point is 1.25
km in the visible channel and 5 km in the infrared. Some details of the GMS-5
satellite can be found at
http://www.nasda.go.jp/sat/gms/index_e.html
A set of matching overlay files showing a latitude and longitude grid and the positions of the coastline are available for the TWP 5km resolution spatial coverage. The overlay files consist of an 'image' of value 1 everywhere, except at the positions of the features (coastlines) in which case the pixel value is zero. Thus the overlays can be written into the image by multiplying them together; the image data remain unchanged and the overlain pixels become zero.
twpgms5coastX1.hdf Overlay of coastlinesFurther details can be obtained at the ARM IOP Browser Site
twpgms5grid1x1X1.hdf Overlay of 1 x 1 lat lon grid
twpgms5grid5x5X1.hdf Overlay of 5 x 5 lat lon grid
The files are in hdf (generated in TeraScan by the tdftohdf routine - see "Data User Notes" for more information about these), and the metadata can be listed using the ncdump -h command of the hdf v3.3r3 release or higher.
Data Stream Names
twpgms5X1.a1
twpgms5grid5x5X1.a1
twpgms5grid1x1X1.a1
twpgms5coastX1.a1
twpgms5lat-lonX1.a1
twplbtm3minnisX1.c1
twplbtm3minnisdarX1.c1
twplbtm3minnismanX1.c1
twplbtm3minnisnauX1.c1
Measurement Description
twpgms5X1.a1.yymmdd.hhmmss.hdf
The visible is averaged from 1.25 km to 5 km. Resolution (IR & Vis) = 5.00 km Image dimensions(IR) = 677 lines x 1114 pixels Projection = Mercator Availability = approximately hourly There are one visible and three infra-red (IR) channels.
| GMS 5 images | Variable | Wavelength | Type | Units | Scale | Offset |
| 1) Visible channel 'albedo' | svissr_vis | 0.75um | byte | albedo*100% | 0.3 | 0 |
| 2) Brightness temperature | svissr_ir1 | 10.8um | byte | temp_deg_c | 0.5 | 188.15 |
| 3) Brightness temperature | svissr_ir2 | 11.5um | byte | temp_deg_c | 0.5 | 188.15 |
| 4) Brightness temperature | svissr_ir3 | 6.9um | byte | temp_deg_c | 0.5 | 188.15 |
| 5) satellite-solar azimuth angle | rel_azimuth | n/a | float | degrees | 1 | 0 |
| 6) satellite zenith angle | sat_zenith | n/a | float | degrees | 1 | 0 |
| 6) solar zenith angle | sun_zenith | n/a | float | degrees | 1 | 0 |
Temporal Coverage
GMS data are available beginning in October 1996. Data are available at the ARM Archive approximately three months after the date generated. The GMS-5 satellite failed and these data are not available after May 21, 2003.
The Minnis products are available as follows:
twplbtm3minnisX1.c1 begin 199980103
twplbtm3minnismanX1.c1 and twplbtm3minnisnauX1.c1 begin 19990616
twplbtm3minnisdarX1.c1 begin 20020401
All these data streams end on 20030521.
Area Covered
twpgms5X1.a1.yymmdd.hhmmss.hdf
East-West = 130oE to 180oE North South = 15oN to 15oS The image is centered over (155 oE, 00oN)
Data Stream Inputs
twpgms5fullX1.00.yymmdd.hhmmss.raw.g5.yyjjj.hhmmThe raw data are shipped to the XDC approximately two months after the date generated.
Notification Form Link
twpgms5X1.00twplbtm3minnisX1.c1
Related Links
This information is currently unavailable.Contacts
ARM Mentor
Richard WagenerARM Software Developer
Laurie GregoryData Source
Institution
SeaSpace CorporationProcessing History
This information is currently unavailable.Reprocessing History
Reprocessing Date
This information is currently unavailable.Start End Reprocessing
This information is currently unavailable.Reason Reprocessing
This information is currently unavailable.FAQ
Question: I would like to have some informations about the HDF formatting of twpgms5X1.a1 data. I have had problems reading the VIS and IR data of these files with the software PCI-GEOMATICS. Customer service of PCI wrote me: "The problem with the HDF file you reported is that the data is 8 bit signed and we only support 8U, 16S, 16U, and 32R." I read the GMS data as 8 bit unsigned (0-255) so could it be possible that they are 8 bit signed?Answer: You have uncovered a bug in the processing software that we use to generate the hdf file. The HDF data type for the infrared and visible imagery is written as "20" (8-bit integer type) whereas it should be "21" (8-bit unsigned integer type).When using Terascan or IDL, the data are read cleanly and the scaling can be correctly applied, but in NoESYS the data are indeed read as signed bytes. A problem notice has been filed with the supplier of the software but in the meantime the following solutions are offered.
(a) If you have TeraScan, use this to read in the data file (reformat using hdftotdf first) and do the analysis in TeraScan, or export the images you need as binary 'flat files' that can be read by most image processing or GIS systems.
(b) If you have IDL use this to read the data and do the analysis in IDL or write binary files. (Peter Minnett has tested this and can send you a simple program to do this if you wish)
(c) If you have Matlab, proceed as in (b) [Peter Minnett has not tested this]
(d) If you do not have access to the licenced software. in (a) (b) or (c), you can use 'hdp' to extract the data from the hdf file. This software is available from http://hdf.ncsa.uiuc.edu/hdftools.html - it's usage is described at http://hdf.ncsa.uiuc.edu/hdp.html and an example is given towards the bottom of http://www.arm.gov/docs/data/files.html. Peter Minnett has tested this. Use the following unix command to extract the 'svissr_ir1' image as a simple binary file called 'ir1.bin' from the hdf file 'twpgms5X1.a1.970307.083100.hdf':
hdp dumpsds -n svissr_ir1 -d -o ir1.bin -b twpgms5X1.a1.970307.083100.hdf
The resulting file is a byte array of dimensions [1114, 677]. This file should be readable by most GIS or image processing software.
Question: What is the relation that I have to use to calibrate the twpgms5X1.a1 data?
Answer: Once you have read the data as a byte array (0 to 255) the scaling of the visible channel to get 'albedo' as a %, multiply the numbers in the array by 0.3
For the infrared images, multiply the numbers by 0.5 and add 188.15 to get brightness temperature in K.
Data User Notes
Note A - there is a known bug in earlier versions of tdftohdf which gives the incorrect data type code, 20, unsigned short integers, instead of 21, for signed short integers. If you use this information in converting the values read from the files to geophysical units, the answer may be wrong as the sign bit is misinterpreted. This affects most of the data currently available through the ARM Archive. Use of the information given in the HDF file header (metadata) gives the correct values.
E.g.: In matlab manually change the output SDS type to uint8 (unsigned 8-bit integer).Example Data
twpgms5coastX1 image Overlay of coastlinestwpgms5grid1x1X1 image Overlay of 1x1 km grid
twpgms5grid5x5X1 image Overlay of 5x5 km grid
twpgms5lat-lonX1 latitude image
twpgms5lat-lonX1 longitude image
Images with latitude and longitude of each pixel
Note: overlay files contain an image that can be overlayed on a gms5 image by multiplying the overlay file and the image file
Quicklook Links
This information is currently unavailable.Glossary
This information is currently unavailable.Acronyms
GMS Geostationary Meteorological Satellite HDF Hierarchical Data Format TDF Terascan Data Format TWP Tropical Western Pacific VISSR Visible and Infrared Spin Scan Radiometer
