Virginia Tech GIS and Remote Sensing Research Symposium

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https://hdl.handle.net/10919/88978

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Browsing Virginia Tech GIS and Remote Sensing Research Symposium by Author "Campbell, James B. Jr."

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    Accuracy Assessment of the National Land Cover Database Impervious Surface dataset for Roanoke, Virginia
    Parece, Tammy E.; Campbell, James B. Jr. (2014)
    The Multi-Resolution Land Characteristics Consortium (MRLC) developed National Land Cover Database Impervious Surface (NLCD IS) data to identify percent developed imperviousness for the coterminous USA. We present the results of an accuracy assessment on this data for the City of Roanoke, Virginia. First, we performed a classic accuracy assessment using a set of random points generated by GIS, and high resolution aerial photographs (1/2 foot resolution), varying the NLCD IS’ percent imperviousness from 10% to 75% per cell, resulting in an overall accuracy of around 70% for most thresholds. Then a polygon impervious surface dataset was delineated in GIS using the same high resolution aerial photos, and subsequently subdivided into 30 meter by 30 meter pixels matching each cell boundary of the NLCD IS data. A second accuracy assessment was performed on a cell by cell basis, comparing the NLCD IS to this newly created impervious surface dataset. Finally, terrain relief, specifically percent slope created from a 30 meter digital elevation model, was added to the analysis to determine if it impacted the accuracy of the NLCD IS data in the cell by cell assessment.
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    Analysis of Crop Phenology Using Time-Series MODIS Data and Climate Data
    Ren, Jie; Campbell, James B. Jr.; Shao, Yang; Thomas, R. Quinn (2014)
    Understanding crop phenology is fundamental to agricultural production, management, planning and decision-making. In the continental United States, key phenological stages are strongly influenced by meteorological and climatological conditions. This study used remote sensing satellite data and climate data to determine key phenological states of corn and soybean and evaluated estimates of these phenological parameters. A time series of Moderate Resolution Imaging Spectrometer (MODIS) Normalized Difference Vegetation Index (NDVI) 16-day composites from 2001 to 2013 was analyzed with the TIMESAT program to automatically retrieve key phenological stages such as the start of season (emergence), peak (heading) and end of season (maturity). These stages were simulated with 6 hourly temperature data from 1980 to 2013 on the basis of crop model under the Community Land Model (CLM) (version 4.5). With these two methods, planting date, heading date, harvesting date, and length of growing season from 2001 to 2013 were determined and compared. There should be a good correlation between estimates derived from satellites and estimates produced with the climate data based on the crop model.