Implementation of Image Restoration Technique for Aqua Moderate Resolution Imaging Spectroradometer (Aqua Modis) Satellite Image

Implementation of Image Restoration Technique for Aqua Moderate Resolution Imaging Spectroradometer (Aqua Modis) Satellite Image

Rosida Vivin Nahari Faculty of Engineering Trunojoyo University Bangkalan, Indonesia

Haryanto Faculty of Engineering Trunojoyo University Bangkalan, Indonesia

Riza Alfita Faculty of Engineering Trunojoyo University Bangkalan, Indonesia

Abstract – Satellite image as a type of data obtained from sensory and stored in certain format should be displayed on the screen for an analysis where quality of the image can be seen clearly. Quality of satellite image is determined based on quantitative and qualitative point of view. Image restoration is needed when quality of particular image cannot meet the requirement of particular application. Basically, all images captured using sensor recording devices have certain errors due to device mechanism, geometrical form, configuration of the earth surface and atmosphere condition when the images are captured. These flaws should be corrected so that geometrical and radio metrical aspects of an image can meet requirements of various types of related application. The purpose of the study is conducting atmospheric restoration technigue for the AQUA MODIS satellite image. The findings show that the restored images have better sharpness level and are clearer. In addition, the AQUA MODIS images that have been through geometrical restoration have been mapped correctly.

Keywords- Restoration ,Remote Sensing, Image Processing

1. INTRODUCTION

   Remote sensing refers to a branch of knowledge and arts that provides information about an object, an area or a phenomenon by analyzing data obtained using certain devices without making direct contact to the object, area or phenomenon being observed (Lillesand dan Kiefer, 1990). Pivotal component in satellite remote sensing is electromagnetic power source, atnosphere, interaction between the power source and object and sensory (Sutanto, 1998. Remote sensing sytem scheme can be seen in figure 1.

   Remote sensing technology, more particularly one using satellite, has been applied extensively to gain information about oceanography and fisheries. Satellite remote sensing is able to provide global information regularly related to condition of certain area of water which refers to (a) ability of satelilite remote sensing to cover large area, (b) satellite remote sensing is homogenous that refers to its ability to cover similar area with the same spatial, scale and geometrical angle (spatial resolution), and (c) record the same earth surface regularly (temporal resolution) (Jansen, 2000 as cited in Purwandaru, 2007).

   Fig. 1. Remote Sensing System

   The main power source used in remote sensing is electromagnetic. Electromagnetic power house is combination of electricity and magnetism that moves with lighting speed in certain frequency and wavelength as well as particular amount of power (Chanlett, 1979 as cited in Sutanto, 1998). Electromagnetic transfer is carried out in three methods namely conduction, convection and radiation.

   For remote sensing of the earth, the most important source of electromagnetic radiation is the sun. The temperature of the sun surface is 6,000 K and it reflects energy that involves wavelength of ultraviolet area, clear and infrared. The dominant wavelength occurs in 0.5 m (green light) that can be seen with naked eyes. It is the result of the sun reflection. Besides that, temperature of the Earth surface is lower, 300 K and based on Wiens displacement law, dominant wavelength changes during longer wavelength that is 9,7 m, placed in thermal infrared area and electromagnetic spectrum.

2. AQUA MODIS SATELLITE

   The MODIS instrument provides high radiometric sensitivity (12 bit) in 36 spectral bands ranging in wavelength from 0.4 µm to 14.4 µm. The responses are custom tailored to the individual needs of the user community and provide exceptionally low out-of-band response. Two bands are imaged at a nominal resolution of 250 m at nadir, with five bands at 500 m, and the remaining 29 bands at 1 km. A ±55- degree scanning pattern at the EOS orbit of 705 km achieves a 2,330-km swath and provides global coverage every one to two days.

   The Scan Mirror Assembly uses a continuously rotating double-sided scan mirror to scan ±55-degrees and is driven by a motor encoder built to operate at 100 percent duty cycle throughout the 6-year instrument design life. The optical system consists of a two-mirror off-axis afocal telescope, which directs energy to four refractive objective assemblies; one for each of the VIS, NIR, SWIR/MWIR and LWIR spectral regions to cover a total spectral range of 0.4 to 14.4

   µm.

   A high-performance passive radiative cooler provides cooling to 83K for the 20 infrared spectral bands on two HgCdTe Focal Plane Assemblies (FPAs). Novel photodiode- silicon readout technology for the visible and near infrared provide unsurpassed quantum efficiency and low-noise readout with exceptional dynamic range. Analog programmable gain and offset and FPA clock and bias electronics are located near the FPAs in two dedicated electronics modules, the Space-viewing Analog Module (SAM) and the Forward-viewing Analog Module (FAM) . A third module, the Main Electronics Module (MEM) provides power, control systems, command and telemetry, and calibration electronics.

   The system also includes four on-board calibrators as well as a view to space: a Solar Diffuser (SD), a v-groove Blackbody (BB), a Spectroradiometric calibration assembly (SRCA), and a Solar Diffuser Stability Monitor (SDSM).

   The first MODIS Flight Instrument, ProtoFlight Model or PFM, is integrated on the Terra (EOS AM-1) spacecraft. Terra successfully launched on December 18, 1999. The second MODIS flight instrument, Flight Model 1 or FM1, is integrated on the Aqua (EOS PM-1) spacecraft; it was successfully launched on May 4, 2002. These MODIS instruments offer an unprecedented look at terrestrial, atmospheric, and ocean phenomenology for a wide and diverse community of users throughout the world.

   Table 1. Technical Specification of Aqua MODIS

   Orbit Type	1:30 pm.ascending node, sun-snchronous, near- polar
   Height	705 km
   Wide View	2,330 km
   Temporal Resolution	1 time/day
   Spatial Resolution	250 m (bands 1-2) 500 m (bands 3-7) 1000 m (bands 8-36)
   Life Span	6 years

   Primary Use	Band	wavelength
   Land/Cloud/Aerosol Boundaries	1	620 670 nm
   	2	841 876 nm
   Land/Cloud/AerosolsProperties	3	459 479 nm
   	4	545 565 nm
   	5	1230 1250 nm
   	6	1628 1652 nm
   	7	2105 2155 nm

   Primary Use	Band	wavelength
   Land/Cloud/Aerosol Boundaries	1	620 670 nm
   	2	841 876 nm
   p>Land/Cloud/AerosolsProperties	3	459 479 nm
   	4	545 565 nm
   	5	1230 1250 nm
   	6	1628 1652 nm
   	7	2105 2155 nm

   (Source: http:// modis.gsfc.nasa.gov/about/specifications.html) Table 2 Spectral information of Aqua MODIS

   Oceancolor/Phytoplankton/Biogeochemi stry	8	405 420 nm
   	9	438 448 nm
   	10	483 493 nm
   	11	526 536 nm
   	12	546 556 nm
   	13	662 672 nm
   	14	673 683 nm
   	15	743 753 nm
   	16	862 877 nm
   AtmosphericWater Vapor	17	890 920 nm
   	18	931 941 nm
   	19	915 965 nm
   Surface/CloudTemperature	20	3.660 – 3.840 m
   	21	3.929 – 3.989 m
   	22	3.929 – 3.989 m
   	23	4.020 – 4.080 m
   AtmosphericTemperature	24	4.433 – 4.498 m
   	25	4.482 – 4.549 m
   Cirrus CloudsWater Vapor	26	1.360 – 1.390 m
   	27	6.535 – 6.895 m
   	28	7.175 – 7.475 m
   Cloud Properties	29	8.400 – 8.700 m
   Ozone	30	9.580 – 9.880 m
   Surface/Cloud Temperature	31	10.780 – 11.280 m
   	32	11.770 – 12.270 m
   Cloud Top Altitude	33	13.185 – 13.485 m
   	34	13.785 – 14.085 m
   	35	13.785 – 14.085 m
   	36	14.085 – 14.385 m

   (Source : http:// modis.gsfc.nasa.gov/about/specifications.html)

   Fig 2. Sample data from Aqua Modis taken on 26 July 2016

   1. Pre-Image Processing

      Image captured using remote sensing method experiences various distortion due to sensory movement, media and the object itself. As the effect, the images require restoration. The procedure is frequently called preliminary data processing or pre-image processing that involves various corrections.

      Geometrical correction refers to process of revising geometrical errors and transforming remote sensing images in order that the images meet certain mapping projection. Geometrical error may occur because of deflecting direction of light, sub-optical system abrasion, non-linear scanning system, change of height and speed of the satellite, change in satellite position, the earth rotation and curve.

      Radiometric error refers to image pixel. It happens due to errors in optical system, disruption of radiation energy in the atmosphere and sun elevation angle. Once radiometric error is not restored, the method used to analyze an image (for example algorithm being developed) cannot be applied to other images taken on different date or place.

      Radiometric correction is needed to standardized angle of sun elevation and the sun-earth distance in different time and place. Radiometric correction for Aqua MODIS image is carried out by counting reflectance value of vivid imaging and that of thermal imaging using the following formula:

      • Zenith censory radiance value:

        Rz = R scalez * iz * pi/180

        with:

        Rz = zenith sensory radiance value R scaleb = radiance scale in zenith sensory iz = zenith sensory

      • Reflectance value: Refb = R scaleb (Bb R offsetb ) with :

   Rb = reflectance value of b R scaleb = radiance scale of b Bb = b channel

   R offsetb = Radiance offsets of b

   Radiance scale and radiance offsets value of the data band used can be seen in Table 3.

   Table 3. Radiance offsets and scale of Aqua MODIS data

   R Rscale B Roffset

   2

   Band	Radiance scale	Radiance offsets
   3	0.00003397	0.00000000
   10	0.00000603	316.97219849
   12	0.00000382	316.97219849
   20	0.00006931	2467.26440430
   31	0.00065081	2035.93322754
   32	0.00057100	2119.08447266
   Zenith Sensory	0.01000000	–

   Band	Radiance scale	Radiance offsets
   3	0.00003397	0.00000000
   10	0.00000603	316.97219849
   12	0.00000382	316.97219849
   20	0.00006931	2467.26440430
   31	0.00065081	2035.93322754
   32	0.00057100	2119.08447266
   Zenith Sensory	0.01000000	–

   Source: Aqua MODIS data attribute (Watts/m /m/sr)

   i i i i

   where:

   Ri = image reflectance/ radiance

   Ri scale = image scale reflectance/ radiance Bi = data band

   Ri offset = offset imaging reflectance/ radiance

   Geometric correction is carried out by analyzing Ground Control Point/ GCP. The process begins with exporting GCP from Aqua MODIS data level 1A to Aqua MODIS data level 1B. Projecting system used is geographic Lat/Lon. The geometric correction process is facilitated using Modis toolbox that can be downloaded freely in www.ittvis.com

3. RESEARCH METHOD

   1. Image Delimitation

      In order to limit the area of the imaging study, image delimitation is carried out. Latitude and longitude are used as the bases. Thus, the scope of the study is images located within the following latitude and longitude, 127º30EL 130º EL and 2º30SL 4º SL.

   2. Radiometric Correction

      Radiometric correction for Aqua MODIS images is carried out by counting radiance and reflectance value of the images with the following equations:

      • Radiance Value: Rb = R scaleb (Bb R offsetb) with:

4. RESULTS AND DISCUSSION

The findings describe comparison between Aqua MODIS images captured on May 16, 2016 and the result of image restoration process on the same date from 2015 to 2016 and selected images captured every month in 2016.

One full scene of Aqua MODIS image record that involves the setting of the study can be seen in figure 3. In order to give clear difference between the land and the ocean, band 721 false color composite is used

Rb = radiance value of b R scaleb = radiance scale of b Bb = b channel

R offsetb = Radiance offsets of b

Fig. 3. Aqua MODIS image captured on May 16, 2016 at 05.15 a.m.

1. Pre-Image Processing (Geometric Correction)

   The result of re-image processing being presented is band 10 image that represents spread of chlorophyll and band 31 image for analyzing temperature of sea surface. Both images can be seen in figure 4 and figure 5.

   .Fig.4. Radiometric Correction in Band 10

   Fig.7. Radiometric Correction in Band 31

   CONCLUSION

   Prior to analysis, the satellite images are restored using both radio metric and geometric corrections. The purpose of radio metric correction is to get clear detail information to avoid errors in interpretation, identification and classification of the satellite image. On the other hand, the purpose of geometric correction is to position satellite image against the world map in order to get an image of which latitude and longitude match the topography and the scale of the map is accurate.

   .Fig.5. Radiometric Correction in Band 10

2. Pre-Image Processing (Radiometric Correction)

Dark substraction method is used in the process and the results are as follow:

Fig.6. Radiometric Correction in Band 10

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