Velpuri, NM, Thenkabail, PS, Gumma, MK, Biradar, C, Dheeravath, V, Noojipady, P, Yuanjie, L (2009). Influence of Resolution in Irrigated Area Mapping and Area Estimation. PHOTOGRAMMETRIC ENGINEERING AND REMOTE SENSING, 75(12), 1383-1395.
The overarching goal of this paper was to determine how, irrigated areas change with resolution (or scale) of imagery. Specific objectives investigated were to (a),mop irrigated areas using four distinct spatial resolutions (or scales), (b) determine how irrigated areas change with resolutions, and (c) establish the causes of differences in resolution-based irrigated areas. The study was conducted in the very large Krishna River basin (India), which has a high degree of formal contiguous, and informal fragmented irrigated areas. The irrigated areas were mapped using satellite sensor data at four distinct resolutions: (a) NOAA AVHRR Pathfinder 10,000 m, (b) Terra MODIS 500 m, (c) Terra MODIS 250 in, and (d) Landsat ETM+ 30 in. The proportion of irrigated areas relative to Landsat 30 in derived irrigated areas (9.36 million hectares for the Krishna basin) were (a) 95 percent using MODIS 250 m, (b) 93 percent using MODIS 500 in, and (c) 86 percent using AVHRR 10,000 In. In this study, it was found that the precise location of the irrigated areas were better established using finer spatial resolution data. A strong relationship (R-2 = 0.74 to 0.95) was observed between irrigated areas determined using various resolutions. This study proved the hypotheses that the finer the spatial resolution of the sensor used, greater was the irrigated area derived, since at finer spatial resolutions, fragmented areas are detected better. Accuracies and errors ,ere established consistently for three classes (surface water irrigated, ground water/conjunctive use irrigated, and non-irrigated) across the four resolutions mentioned above. The results showed that the Landsat data provided significantly higher overall accuracies (84 percent) when compared to MODIS 500 in (77 percent.), MODIS 250 in (79 percent), and AVHRR 10,000 m (63 percent).