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GPM Ground Validation DC-8 Nadir-Oriented Camera GCPEx Table of Contents
The GPM Ground Validation DC-8 Nadir-Oriented Camera data set contains geolocated visible wavelength imagery of the ground obtained over Ontario, Canada during the GCPEx campaign. The data was collected on a cloud free flight day (February 20, 2012) in order to measure surface emissions. Therefore, this data set may be useful in determining snow cover and lake ice cover for emissivity studies in conjunction with CoSMIR data, for example. In addition, aircraft navigation information are included in the data set files for convenience and reproducibility. Finally, ground temperature measurements are also included in the files to aid in emissivity retrievals. CampaignThe GPM Cold-season Precipitation Experiment (GCPEx) occurred in Ontario, Canada during the winter season of 2011-2012. GCPEx addressed shortcomings in the GPM snowfall retrieval algorithm by collecting microphysical properties, associated remote sensing observations, and coordinated model simulations of precipitating snow. These data sets were collected to aid in the achievement of the over arching goal of GCPEx which is to characterize the ability of multi-frequency active and passive microwave sensors to detect and estimate falling snow. Further details on GCPEx are available at http://gpm.nsstc.nasa.gov/gcpex. Information on the Global Precipitation Measurement (GPM) mission is available at http://pmm.nasa.gov/GPM. The GPM Ground Validation nadir-looking camera imagery was recorded by an Axis 223M network camera. This commercially available camera has the following specifications:
Additional information on the Axis 223M camera can be found at http://www.axis.com/files/datasheet/ds_223m_32713_en_0809_lo.pdf. During GCPEx, imagery was recorded by the nadir-looking camera on February 20, 2012, which was a clear air flight day. The video was recorded at a resolution of 1280x720 pixels and 30 Hz at the maximum zoom (38 degree field of view). At the DC-8's average cruising altitude of 10 km and ground speed of 200 m/s, this provides a nadir resolution of 9.2 meters. Only the central scan of each frame was processed for geo-location. Ground temperatures were also measured
with a nadir-pointing infrared thermometer. The measurements were
obtained with the commercially available PRT-5 thermometer. The
specifications for the thermometer can be found at http://www.pyrometer.com/oceantemperature.html. Joe Munchak The DC-8 Camera data files are HDF5 (Hierarchical Data Format) and are named with the following convention:
where,
Data files are in HDF5 (Hierarchical Data Format). The files are divided into 15-minute segments to reduce individual file size. Start time is indicated in the file name. File contents include RGB byte values for each pixel, timestamps for each scan, aircraft navigation for every second, and geospatial locations (latitude/longitude) for each pixel. Absolute navigation errors of up to 1000 meters are possible when aircraft roll is less than 3 degrees in magnitude (greater errors may occur during times of greater roll magnitude). It is recommended to compare imagery to a high-resolution land/water mask to ensure that geolocation is accurate in the region of interest. More information about HDF5 may be found at the HDF group home page.
In addition, read software has been provided by the P.I. to assist in
processing the data. The code for the program can be found at https://gpm.nsstc.nasa.gov/gpm_validation/gcpex/dc8_camera_nadir/doc/read_nadircam.pro. Our data sets are provided through the NASA Earth Science Data and Information System (ESDIS) Project and the Global Hydrology Resource Center (GHRC) Distributed Active Archive Center (DAAC). GHRC DAAC is one of NASA's Earth Observing System Data and Information System (EOSDIS) data centers that are part of the ESDIS project. ESDIS data are not copyrighted; however, in the event that you publish our data or results derived by using our data, we request that you include an acknowledgment within the text of the article and a citation on your reference list. Examples for general acknowledgments, data set citation in a reference listing, and crediting online web images and information can be found at: http://ghrc.nsstc.nasa.gov/uso/citation.html To order these data or for further information, please contact:
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