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TSTool Documentation Introduction - 3 2.2 Time Series Objects and Identifiers TSTool handles time series as objects that are read (or internally created), manipulated, viewed, and output. T ime series data include properties (also referred to as attributes or metadata) and a series of date/time and data value pairs (and optionally value data flags). Data generally consist of floating point values; however, time series may contain other data such as strings or image s. TSTool primarily focuses on numerical time series . T ime series are defined either as regular interval (equal spacing of date/time) or irregular interval (e.g., infrequent measurements). Regular time series lend themselves to simpler storage and faste r processing because date/time information only needs to be stored for the endpoints and processing is less complicated . TSTool defines each time series as having an interval base and multiplier (e.g., 1Month , 24Hour ). In many cases, the multiplier is 1 and is not shown in output (e.g., Month rather than 1Month is shown). In addition to a period of record, interval, and data valu es, time series properties include: • Units (e.g., CFS ) • Data type (e.g., Streamflow ) • Data limits (the maximum, minimum, etc.) • Des cription (generally a station or structure name) • Missing data value (used internally to mark missing data and trigger data filling, often –999 or NaN [Not a Number]) • Comments (often station comments, if available) • Processing history (a list of comments abo ut how the time series was created and manipulated) To identify time series in the original data and manage time series internally , TSTool assigns each time series a time series identifier (TSID) that uses the notation: LocationType:Location.Source.Type.Interval.Scen ario[Seq]~InputType~InputName LocationType:Location.Source.Type.Interval.Scenario[Seq]~DataStoreName The TSID can be thought of as a unique resource identifier, similar to a URL for web resources. The first five parts (Location.Source.Type.Interval.Scenario ) are use d to identify time series within the original data (e.g., to find the time series in a file or database): • Location Type – o ptionally used where necessary to uniquely identify locations (e.g., use a location type of Basin or Subbasin where other identi fier information would result in ambiguous interpretation of the identifier parts • Location – typically a physical location identifier , such as a station, basin, or sensor identifier. • Source – a data provider identifier, usually a g overnment or system identifier (e.g., USGS , NWS ), necessary because sometimes the provider for a location changes over time or a database may contain time series from multiple data providers • Type – the data type, typically specific to the data (e.g., Streamflow , Precip ) – TSTool does not try to institute global data type definitions). • Interval – the data interval, indicating the time between data values (e.g., 6Hour , Day , Irregular ). • Scenario – an optional item that indicates a scenario (e.g., Hist , Filled , Max , Critical ). 15