Overview

The UDF IDL interface mirrors the UDF C-Interface but at a slightly higher level, the main difference between the two being scope. The C-Interface returns a single measurement from a UDF definition at the current time each time it is called whereas the UDF IDL interface returns all of the available UDF measurements available for the current time.

To do this the UDF IDL Interface uses the UDF PIDF file to determine which measurements are provided by the UDF and what units have been defined for each measurements. Only measurements defined within the PIDF are accessible through the interface and only the units defined under each measurement in the PIDF are available for return.

The PIDF groups the available measurements into different categories which for the most part echo the VIDF definitions for the measurements. The exception is the PIDF Sensor Block which can include measurements which in the VIDF are labeled both as sensor data and ancillary data. The UDF IDL Interface treats data according the their VIDF definitions. This is an important point to remember especially when the UDF IDL Interface is requested to return the UDF sensor data blocked within various arrays. The UDF IDL Interface defines sensor measurements as data which is both located within the PIDF sensor block and which is defined in the VIDF as sensor data. Measurements within the PIDF sensor block which have a VIDF ancillary data orgin are treated at ancillary data. This is the definition of sensor measurements which will hold throughout this document unless otherwise noted.

In all cases, measurements are placed into the IDL UDF data structure in the order in which they are encountered in the PIDF file. Ancillary measurements located within the PIDF sensor block are the first measurements in the Ancillary data group.