In HEC-DSS, both time-series and grid records consist of an array of sequential numerical values and an associated header describing the data in the array.  In a time-series record, the value array represents the variation of a parameter’s value through time at a fixed location.  In a grid record, the value array represents the variation of a parameter’s value through a range of locations (i.e., a region of the earth’s surface) for a single interval of time.  The header array of a grid record contains information about the parameter values (their units and some summary statistics) and the two-dimensional region that they represent (the number of rows and columns in the array, and the location of the grid in geo-referenced coordinates).


The contents of the grid header are described below for four types of grid records in DSS.  The grid header types are:


  • UNDEFINED—containing basic parameter and grid extent information, which is common to all grid types.
  • HRAP—for US National Weather Service NEXRAD grids.
  • Albers Equal-Area—including SHG grids.
  • Specified Grid Info—a general-purpose grid type which contains a complete description of the Spatial Reference System (SRS) in which the grid’s location is defined.


The HRAP and Albers grid headers contain additional descriptive information specific to those grid types.  The Specified Grid Info header is potentially capable of describing grids in any coordinate system, including HRAP and SHG (Albers).