PRIMEWIN: Processing of Images on Windows

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## Regional Remote Sensing Centre-Central, NAGPUR

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# OCM Processing: OCM-1 data analysis Module

Oceans occupying 70% of the Earth’s surface greatly influence the global climate effecting the economy and day-to-day life of the people. Improved observations of the physical and biological parameters of oceans have, thus, become important for any meaningful study of the Earth’s environment itself. The conventional means of these observations using ships, buoys and other in-situ methods is both difficult and expensive, and often not feasible at all. The synoptic observations from space-borne sensors, frequent enough to resolve the dominant scale of variation over the oceans in space and time, provide the most viable means for making for making these measurements over large tracts on an operational basis. Understanding the importance of ocean related studies; ISRO has launched a dedicated satellite IRS – P4 (OceanSat-I). The repeat cycle of two days enables research in various applications of ocean biology and physical oceanography like

· Identification of potential fishing zones with increased reliability

· Modeling primary production for fish stock assessment and assessment of the role of ocean in removing CO2 from atmosphere

· Study of toxic and non-toxic algal bloom and their impact on fishery

· Study of coastal applications like assessment of sediment transport along the sea

· Water quality mapping for pollution studies, oil spill detection etc

OCM has spectral bands selected for oceanographic studies. Out of total eight spectral bands, five are in the visible part of the electromagnetic spectrum for retrieval of oceanic parameters like Chlorophyll, suspended sediments, Yellow substance, diffuse attenuation coefficient etc. Models have been developed for atmospheric correction of the data and retrieval of parameters mentioned.

This module enables extraction of various ocean related parameters from OCM data in a user-friendly manner. Algorithms for parameter extraction have been provided by Space Applications Centre, Ahmedabad.

· Downloads OCM data from CD along with header information on Lat/Long, Sun angle, Sun azimuth and related parameters.

· Computation of Chlorophyll, yellow substance and suspended sediments, Aerosols and water leaving reflectance

Follow the sequence of steps shown below for OCM data processing:

This module will create following files:

Filename_chl : Chlorophyll

Filename_chllog : Log dump of Chlorophyll values

Filename_yel : Yellow substance

Filename_sus : Suspended Sediments

Filename_aer : Aerosol

Filename_rfk1 to _rfl5 : Water leaving reflectance

· For viewing parameters with predefined standard colors

· Filename_chl (Chlorophyll) - Load the data in viewer; apply logarithmic stretch; Apply standard colors rendering through Pseudo Color tool.

· Filename_chllog (Log dump of Chlorophyll values) - Load the data in viewer; Apply standard colors rendering through Pseudo Color tool.

# OCM Processing: OCM-2 data analysis Module

Presently two modules are developed ‘OcmRead’ and ‘OceanParams’

OcmRead:

IRS Q2 OCM Data is supplied in HDF Format. This module reads the data in HDF format and converts in to a general purpose image format ‘.tif’. Also extracted is ancillary information from the HDF file and presented to the user in text format. The GUI is as depicted below. Parameter retrieval algorithms will use some of the files generated by this module.

OceanParams

This module is used to retrieve Ocean parameters like Chlorophyll, Suspended Sediments, Yellow Substance, Aerosol and Water leaving radiance. The inputs for this program are the ‘.tif’ generated using the above ‘OcmRead’ module or the HDF file itself containing the raw IRS Q2 OCM data. The user interface is as depicted below. The output is in the form of ‘.tif’ file.

Supplied Along with these modules is ‘wind’ directory, containing the wind speed data files. Parameter retrieval algorithms make use of these files. In case of Chlorophyll, an additional ‘log’ applied image will be prepared.

The facility for choosing the Algorithm is also provided. Even provision is there for the user input of the coefficients used in the algorithm. The GUI for Algorithm choosing is given below.