Lisini G.,Centro Studi Rischio e Sicurezza |
Gamba P.,University of Pavia |
Dell'Acqua F.,University of Pavia |
International Journal of Image and Data Fusion | Year: 2011
In this article, we introduce a unitary approach to road extraction in wide area images, obtained by means of satellite sensors in both the optical/infrared and microwave domains. Despite the large amount of methodologies discussed in technical literature for road extraction, they have been mostly tested on relatively small portions of satellite images. Moreover, in many cases, the method targeted an optical or a synthetic aperture radar (SAR) image, and a unitary strategy is missing. This study is aimed at bridging these gaps and provides a unique framework for the extraction of roads with different characteristics using optical or SAR data sets. The approach exploits a multi-scale analysis to adapt to the different resolutions of data and a pre-processing step to adapt to the different wavelengths of data. When possible, the framework allows the fusion of the road networks extracted from optical and SAR data of the same area. The soundness of the approach is proved by means of the analysis of Landsat and ALOS data of an area in Congo. © 2011 Taylor & Francis.
Pazhanivelan S.,Tamil Nadu Agricultural University |
Kannan P.,Tamil Nadu Agricultural University |
Christy Nirmala Mary P.,Tamil Nadu Agricultural University |
Subramanian E.,Tamil Nadu Agricultural University |
And 6 more authors.
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives | Year: 2015
Rice is the most important cereal crop governing food security in Asia. Reliable and regular information on the area under rice production is the basis of policy decisions related to imports, exports and prices which directly affect food security. Recent and planned launches of SAR sensors coupled with automated processing can provide sustainable solutions to the challenges on mapping and monitoring rice systems. High resolution (3m) Synthetic Aperture Radar (SAR) imageries were used to map and monitor rice growing areas in selected three sites in TamilNadu, India to determine rice cropping extent, track rice growth and estimate yields. A simple, robust, rule-based classification for mapping rice area with multi-temporal, X-band, HH polarized SAR imagery from COSMO Skymed and TerraSAR X and site specific parameters were used. The robustness of the approach is demonstrated on a very large dataset involving 30 images across 3 footprints obtained during 2013-14. A total of 318 in-season site visits were conducted across 60 monitoring locations for rice classification and 432 field observations were made for accuracy assessment. Rice area and Start of Season (SoS) maps were generated with classification accuracies ranging from 87-92 per cent. Using ORYZA2000, a weather driven process based crop growth simulation model; yield estimates were made with the inclusion of rice crop parameters derived from the remote sensing products viz., seasonal rice area, SoS and backscatter time series. Yield Simulation accuracy levels of 87 per cent at district level and 85-96 per cent at block level demonstrated the suitability of remote sensing products for policy decisions ensuring food security and reducing vulnerability of farmers in India.
Asilo S.,University of Twente |
Asilo S.,International Rice Research Institute |
de Bie K.,University of Twente |
Skidmore A.,University of Twente |
And 3 more authors.
Remote Sensing | Year: 2014
Different rice crop information can be derived from different remote sensing sources to provide information for decision making and policies related to agricultural production and food security. The objective of this study is to generate complementary and comprehensive rice crop information from hypertemporal optical and multitemporal high-resolution SAR imagery. We demonstrate the use of MODIS data for rice-based system characterization and X-band SAR data from TerraSAR-X and CosmoSkyMed for the identification and detailed mapping of rice areas and flooding/transplanting dates. MODIS was classified using ISODATA to generate cropping calendar, cropping intensity, cropping pattern and rice ecosystem information. Season and location specific thresholds from field observations were used to generate detailed maps of rice areas and flooding/transplanting dates from the SAR data. Error matrices were used for the accuracy assessment of the MODIS-derived rice characteristics map and the SAR-derived detailed rice area map, while Root Mean Square Error (RMSE) and linear correlation were used to assess the TSX-derived flooding/transplanting dates. Results showed that multitemporal high spatial resolution SAR data is effective for mapping rice areas and flooding/transplanting dates with an overall accuracy of 90% and a kappa of 0.72 and that hypertemporal moderate-resolution optical imagery is effective for the basic characterization of rice areas with an overall accuracy that ranged from 62% to 87% and a kappa of 0.52 to 0.72. This study has also provided the first assessment of the temporal variation in the backscatter of rice from CSK and TSX using large incidence angles covering all rice crop stages from pre-season until harvest. This complementarity in optical and SAR data can be further exploited in the near future with the increased availability of space-borne optical and SAR sensors. This new information can help improve the identification of rice areas.
Milisavljevic N.,Royal Military Academy |
Holecz F.,SARMAP |
Bloch I.,Orange S.A. |
Closson D.,Royal Military Academy |
International Geoscience and Remote Sensing Symposium (IGARSS) | Year: 2012
The aim of the approach proposed in this paper is to determine a potential crop extent prior to the crop season, by determining regions that might change in time vs. those that surely do not change. We use multi-annual PALSAR-1 data since in dry conditions, L-band HH/HV data have a potential of distinguishing between bare soil and other classes. In addition, a more accurate map can be reached with multi-temporal data than using a single date. We work on HH and HV data sets separately and analyze the two outputs using ground-truth information. In a final phase, we combine these two outputs and compare the result with the ground-truth too, to test the usefulness of fusing the HH/HV information. This approach is the first step in our three-step procedure for estimation of cultivated area in small plot agriculture in Malawi. Validation results show that the proposed approach is promising. © 2012 IEEE.
Chen L.,Peking University |
Qin Q.,SARMAP |
Chen C.,Orange S.A. |
International Geoscience and Remote Sensing Symposium (IGARSS) | Year: 2012
Remote sensing technology is considered a fast and effective method to prospect ore. Now, this method is used in Gejiu tin deposit of YunNan in order to extract more accurate mineralization abnormal information. In this study, first through the band math method and principal component analysis method, the mineralization alternation can be extracted in ETM data. Then using ASTER data the limonitization, the chloritization and the dolomitization are extracted by the spectral angle method. At last, the trace elements of the vegetation are statistically analyzed and the vegetation mineralization alteration information is extracted by two different methods in ASTER data. The result shows that the alternation information distributions are consistent in the east-south study area and match with the field exploration. Consequently the extracted results are effective. © 2012 IEEE.