Phenological Observations On Classical Prehistoric Capital Sites In The Middle And Lower Reaches Of The Yellow River Based On NDVI Time Series

Buried archeological features show up as crop marks that are mostly visible using high spatial resolution image data.Such data are costly and restricted to small regions and time domains.However,a time series of freely available medium resolution imagery can be employed to detect crop growth changes to reveal subtle surface marks in large areas.MODIS data can provide lots of phenological inforrmations of crops grows because of its high time resolution,but it is rarely used for archaeological prospection primarily due to its coarseness and inability to detect subtle features.To fill the gap,classic prehistoric capital settlement sites of Taosi and Erlitou,with a large area of the classic features of prehistoric ruins,are taken as the research objects,and the application of MODIS NDVI time series data to observe the the phenological growth of crops for each site and detect the growth differences of each phenological periods.MODIS NDVI rate of change covering 230 periods of 10 years were computed and analyzed by Pearson's correlation coefficient.In addition,the max-minimal distance was employed to measure the similarities of crop growth within archaeological sites.On the other side,burial areas(such as the palace area and the sacrificial area)in the site were selected as the research area while the surrounding empty fields with a low density of ancient features were used as reference regions.Landsat NDVI covering two years' growth periods of wheat and maize were computed and analyzed using Pearson's correlation coefficient and Euclidean distance.Similarities or disparities between the burial areas and their empty areas were computed using the unidirectional Hausdorff distance to determine optimum periods for detection and monitoring.Based on the phenology of crop growth,the time series NDVI images of winter wheat and summer maize were generated to analyze crop anomalies in the archeological sites.Results show that both the Max-minimal and the unidirectional Hausdorff distance are higher during the critical stages of water for both crops while the Landsat NDVI images of these stages show the crop anomalies caused by the burial archeological features.This indicates that the Hausdorff distance method on NDVI time series images can use to detect the crop anomalies.It is also illustrated that the Landsat NDVI images of critical stages of water can provide information under the subsurface and MODIS can provide useful crops growth information before field excavations.