Evaluation of approaches for AWiFS multi-date registration R.D. Garg * , Shefali Agrawal, V.K. Dadhwal Indian Institute of Remote Sensing, 4 Kalidas Road, Dehradun 248001, India Received 1 June 2007; accepted 14 January 2008 Abstract AWiFS onboard IRS-P6 belongs to the category of high-repetivity sensors based on large swath, but with ground trace based on narrow-swath sensor (LISS-III). This is useful for cloud removal as well as vegetation phenology studies. Such multi-date analysis has a prerequisite of accurate multi-date registration. This study investigates the accuracy of multi-date registration over a mixed plain and hilly terrain in northern India (29–318N latitude and 77.5–79.58E longitude; 200–4000 m.a.s.l.). Simple polynomial rectification, multi-date registration using ortho-correction technique on standard product (level-2) and radiometric product (level- 1) as a function of number of ground control points (GCPs) and external Digital Elevation Model (DEM) were investigated. The results indicated that ortho-rectification on level-1 product provided better accuracy in comparison to simple rectification and ortho- rectification on level-2 product. # 2008 Elsevier B.V. All rights reserved. Keywords: AWiFS; Geo-correction; Ortho-correction; Multidate registration 1. Introduction Multi-temporal Remote Sensing data is widely acknowledged as having significant advantages over single date imagery for crop inventory, vegetation phenology and a number of process-based studies (Townshend et al., 1985). Many applications, viz. disaster management, precision farming, require multi- date satellite imagery. On Indian Remote Sensing satellites, two wide-swath sensors have been placed: WiFS (Wide Field Sensor) on IRS 1C/1D and AWiFS (Advanced Wide Field Sensor) on IRS P6. These share high repetivity with sensors such as OCM (Ocean Colour Monitor), SPOT Vegetation, Modis, etc., but have high-spatial resolution. Any analysis with data sets of these sensors requires multi-date registration. IRS 1C/1D WiFS is a large-swath, high-repetivity camera designed specifically for vegetation and agri- cultural monitoring applications (Joseph, 1996; Pandya et al., 2000). Demonstrated approaches with WiFS are forest cover assessment, vegetation and crop phenology studies, wheat crop acreage estimation, land use/land cover mapping, drought crop discrimination and inventory, etc. (Joshi et al., 2001; Bhagia et al., 1997; Oza et al., 1996; Rajak et al., 2002; Singh et al., 1999). Although WiFS data has proved its utility for regional level studies, but it has relatively coarser spatial resolution. AWiFS camera with a spatial resolution of 56 m and covering a swath of 740 km is an improved version compared to the WiFS camera. AWiFS data has also been used for many applications such as national level mapping under National Resource Repository (NRR) project with multi-temporal AWiFS data sets for land use/land cover mapping (NRSA, 2006). In order to cover the 740 km wide swath, AWiFS camera is split into two separate electro optic modules, AWiFS-A and AWiFS-B, which are tilted by an angle of www.elsevier.com/locate/jag International Journal of Applied Earth Observation and Geoinformation 10 (2008) 175–180 * Corresponding author. Tel.: +91 1332 285893; fax: +91 1332 273560. E-mail address: rdgarg@hotmail.com (R.D. Garg). 0303-2434/$ – see front matter # 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.jag.2008.02.011