7/31/2019 Mapping and monitoring rice areas using multi-sensor multi-temporal Synthetic Aperture Radar (SAR) imagery

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In the Philippines, rice is cultivated on 2.76 million ha, much of which is cropped

twice a year. In spite of this, production is not enough to meet increasing domestic

demand. Information on the location and extent of rice areas is critical to rice

importation decisions and in prioritizing research and extension activities such as

dissemination of location-specific technologies.

This study explores the use of multi-temporal SAR images to map the rice-growing

areas of the major rice-producing provinces in the Philippines throughout 2011.

SAR is a remote sensing system that

provides its own source of energy and

illumination. The sensor transmits

microwaves toward the target and then

records the energy that is reflected back

to the sensor aboard the satellite.

SAR has an all-weather imaging

capability that makes it ideal for

mapping tropical areas.Fig. 1. Basic principle of SAR.

RICEscape, developed by sarmap, is a dedicated processing chain th

enables fully automatic SAR data pre-processing (specifically tuned for ric

detection purposes) and further mapping and monitoring of rice areas.

We are using multi-temporal images taken by different SAR sensors

adequately capture flooding and emergence/transplanting dates.

Mapping and monitoring rice areas

Table 1. Description of SAR data used.

Sensor Banda Spatial

resolution (m)

Revisit

period (d)

Polarizationb

ENVISAT ASAR C 15 to 25 35 HHALOS-PALSAR L 8 to 15 46 HH - HH/HV

Cosmo SkyMed

(CSK,1-4)

X 15 1 to16 HH

Fig. 4. 2010 multi-sensor image composite over Cagayan (Nov 26 PALSAR in red, Nov 23

ASAR in green, Dec 30 CSK in blue). Blue-colored areas represent rice at vegetati ve stage b

the second half of December, whereas green areas were still flooded by the end of December.

Fig. 2. Top 20 rice-growing provinces and monitoring sites (A) and coverage of acquired SAR images (B,C,D) for 2011

dry season.

Planting dates vary widely, highlighting the importance of acquiring multi-

temporal images for monitoring rice areas.

Flooding and crop emergence/transplanting can be easily detected using multi-

temporal images taken by different SAR sensors.

Preliminary findings

This monitoring site in Nueva

Ecija (red polygon) is located in

Brgy. Casile, Llanera. It covers

an area of 2.95 ha, transplanted

on 27-29 Dec 2010 with RC216.

Conclusions

Multi-temporal and multi-sensor acquisitions are required to properly capture,

the country level, the critical stages - such as flooding and emergenc

transplanting dates - that vary widely in time and space.

1 International Rice Research Institute, Los Baos, Laguna, Philippines2 Philippine Rice Research Institute, Science City of Muoz, Nueva Ecija, Philippines3 sarmap, Cascine di Barico, CH 6989 Purasca, Switzerland

J.V. Raviz1*, E.J.P. Quilang2, M. Barbieri3, E.D. Alosnos2, S.L. Asilo1, G.D. Balleras2, A.C.M. Baradas2, R.T. Dollentas2, E.L. Dupitas2, N.D. Ganotisi2, F. Holecz3, A.G. Laborte

M.O. Mabalay2, J.M. Maloom2, A.A. Maunahan1, J.R.F. Mirandilla2, A. Nelson1, A.B. Rala1, G.V. Romarez2, A.C. Suer2, B.M. Tabudlong2, F.L. Varquez2, J.R.M. Vergara

Fig. 5. CSK ScanSAR images over Nueva Ecija, darker areas are flooded fields (A) dark areas

became bright after transplanting (B), and brighter at tillering stage (C). Photos show actual field

conditions.

B

PALSAR

C

CSK

D

ASAR RICEscape processing chain

Fig. 3. General procedure for rice mapping in RICEscape.

(B) Jan 2, 2011

(C) Jan 18, 2011

Dec 15, 2010

Jan 4, 2011

Jan 31, 2011

2010-11 multi-temporal image

composite over Nueva Ecija

(Dec 17 in red, Jan 2 in green,

Jan 18 in blue). Rice emergence

is detected first in cyan (late

December to early January)

then in blue areas (mid-

January). Red and green areas

are still flooded during thisperiod. The use of multiple radar wavelengths allows better detection of rice growthroughout the whole crop season.

aBand C operates on 5.6cm, L on 23.6cm, and X on 3cm wavelength in the microwave section o

the electromagnetic spectrum. bHH is horizontal transmit and horizontal receive, HV i

horizontal transmit and vertical receive.

When completed, this project will provide the first SAR-based high-spatiaresolution map of rice areas covering the major rice-producing provinces in th

Philippines.

With the launch of Sentinel-1A and 1B (ESA C-band missions), planned fo

2012-13, the temporal acquisition frequency (revisiting cycle 7 days) will enabcontinuous rice growth monitoring at the country level. C-band data from

Sentinel will also be provided free of charge.

(A) Dec 17, 2010

DEM

Standard format original

SAR products

Multilooking + Filtering

Geometric calibrationRadiometric calibration

Radiometric normalization

Filtering

Rice map

Pre-proc

essing

Classification Validation

using ground

truth dataMonitoring sitesTop 20 rice growing provinces

Legend

A