NovaStar 5 Basic Concepts

The operation of NovaStar 5 requires an understanding of some basic concepts and terminology which are introduced here and used throughout the document.

• Station: Each station is uniquely identified by its name, coordinate location (latitude/longitude), and station numerical identifier (ID). Acceptable legacy ALERT station ID numbers can range from 0 to 8191. NovaStar5 can accept station ID numbers from 0 to 99,999,999. Other systems that share data may equivalently use the term "site" or "location". Stations can also be used to manage data for areas (e.g., for average precipitation), system components such as base station and repeaters (for system metrics), forecast locations, and synthetic locations where data are managed.

  • Station Type: Each station is associated with a datalogger/data collection unit/transmitter installed at the station (HydroLynx 5096, Sutron 8210, Handar 555, HydroLynx 50386, etc.). In NovaStar 5, station types describe attributes of this equipment that are common to similar stations.

  • Tag Name: A station tag is an alternate text identifier that can be used as an alternative to the numerical identifier. The tag name is often displayed on maps and is used for data export. For example, use the tag name for "Handbook 5" identifier used with Standard Hydrologic Exchange Format (SHEF) data export.

  • Remote Tag: The remote tag is an identifier for remote system, typically used when importing data from a remote system. For example, use when importing data from the United Stated Geological Survey (USGS).

• Point: A station may have a number of different sensors installed, and in NovaStar 5 these data sources associated with a station are referred to as "points". Examples of installed sensors at a station include battery voltage, rain gage, pressure transducer to monitor water level, wind speed/direction sensor, air temperature sensor, and relative humidity sensor. Point data may also be obtained from other external sources, for example when data is obtained via satellite or web. The data packets provided by most of these stations contain one measurement per remote sensor identifier. Some exceptions are digital status (multiple digital inputs per data value transmission) and ALERT wind (wind run and wind direction are combined in one value transmission). When these compound sensor data reports are received, the data value is parsed to store individual sensor data values in the points assigned to the remote sensor identifier. A point represents a single measurement data stream in the database; either a data value received from a remote sensor or a computed or derived value. Synthetic points can also be configured to contain the results of equations or imported data.

  • Point Type: A point type characterizes the data values returned from a remote sensor. Sensors producing data values of a similar nature are associated with point types to facilitate configuration of the system, definition of alarm levels, and display of data. Point types specify the default data associated with a point, including data units, calibration (converts raw data to scaled/engineering data) and data checking such as range checks. Standard point types are typically provided during system setup and can be further edited by the administrator. An important property of point type is Standard Hydrologic Exchange Parameter physical element code, which provides a common definition of data type and duration.

  • Data Type: Each point corresponds to a sensor parameter. To facilitate use of the data, a human-readable data type is used, which is a longer version of the Standard Hydrologic Exchange Format (SHEF) physical element code. For exmaple, a point with numerical identifier 103 measures river water level and has SHEF code HG and longer data type WaterLevelRiver. NovaStar 5 users may have traditionally used the point numerical identifier or description to identifier data; however, the longer data type is increasingly being used to provide data to a larger community of data users.

  • Calibration: A calibration is a collection of values that are used to convert raw sensor data into scaled point data in the desired engineering units before storing in the NovaStar 5 database. Most NovaStar 5 functionality such as alarms and data displays focus scaled values. Calibrations are defined with an effective time so that calibrations can change over time.

• Alarm: An alarm is a data record that indicates when point data values have met a criteria condition defined by an alarm trigger. When an alarm is triggered, it can be acknowledged through human interaction or can be automatically reset based on a time interval.

  • Alarm trigger: An alarm trigger defined criteria for evaluating data for critical conditions. For example, alarm triggers can be defined for upper or lower limit values and increase or decrease rates. Alarms triggers can also be defined for "no data report" interval. The reset interval for an alarm trigger is generally defined consistent with the data type based on typical event length for the data type. For example, a high precipitation event can generally be automatically reset based on a time interval for typical storm lengths.

  • Alarm group: Points producing data values that can be evaluated for alarm conditions using the same criteria are grouped into an alarm group. An alarm group assigns the same alarm threshold criteria and trigger values to multiple points. For example, an alarm group may be defined containing all batteries in order to check for voltage outside a normal range. The group is then assigned a low limit voltage alarm level, typically 11.0 volts. Incoming data for any battery in the group is checked against the alarm level defined for the group. The alarm group concept facilitates the configuration and display of alarm conditions for multiple sensors with similar alarm conditions. Another example is precipitation amounts such as X inches/hour. Alarm groups are not typically used for data types where alarm criteria vary by location, including water level and discharge.

• Time Series: A time series is a temporally sequential grouping of data that are displayed on a consistent time step (regular interval time series) or inconsistent time step (irregular interval time series). NovaStar data are by default internally managed as instantaneous (irregular interval) time series, although the database can be configured to generate and import interval data.

  • Location Identifier: Each time series has a location identifier, for example the station numerical identifier.

  • Data Type: The time series data type is consistent with the point data type. The SHEF code indicates the data type (SHEF parameter code) and duration of the measurement. The duration is equivalent to the data interval described below.

  • Data Interval: The data interval for a time series is "irregular" (or "irreg") for instantaneous data data, or consists of a base interval and multiplier, such as "5-minute" (or "5min"). The timestamp for each data interval corresponds to instantaneous measurement or interval-ending time for interval data. For example, the timestamp for hourly data would indicate the ending hour for average streamflow discharge over the previous hour.

  • Display Interval: The display interval is used to create time series information from irregular-interval data for display purposes. ALERT and other data reports are received on irregular time intervals and are stored within the database as such. The display interval can range from 5 minutes to 1 year. Data retrieval for displaying/exporting interval data can be configured to carry forward the last observed value, for example water level. For example, irregular data can be converted to 5-minute interval data, where 5-minute values are repeated for acceptable period.

  • Period: A period is a span of time indicated by starting date/time and ending date/time. A is often specified to indicate the time span over which an analysis occurs.

• Ratings: A rating is defined by a rating table or equation and allows converting data to another type. Ratings are applied to scaled data. Ratings are defined with an effective time and can therefore vary over time. Each point allows up to five rated values.

  • Rating Table: A rating table is a list of input and output value pairs. Input point data are compard to the input values in the rating table and corresponding output value is estimated. If necessary, the values are interpolated, or extrapolated. Rating tables are often used to convert water level (stage, depth) to discharge.

  • Rating Equation: In contrast to a rating table, a rating equation provides a an estimate of output values over a continous range of input. A rating equation is typically developed by fitting a curve to rating table data, in particular to estimate values below or above the extreme values in the rating table.

  • Rating Assign: NovaStar allows rating tables and equations to be defined and reused for multiple points. The "rating assign" associates a point with a rating table or equation.

  • Rating Shift: A shift can be associated with a rating assign and essentially shifts a rating vertically. The values in a rating table or equation are shifted to better fit the observed data.