Real Time DGPS Data Acquisition of Airborne Vehicle and Display software in Integrated test range

R Appavu Raj
R Appavu Raj
DD(RS)

A K L Bhagat
A K L Bhagat
Scientist

Sunit Kumar Gupta
Sunit Kumar Gupta
Scientist

Integrated Test Range Chandipur,
Defence Research and Developmental Organization, India
Range Safety Wing, Integrated Test Range Chandipur,
Balasore – 756025, Orissa, India
Email: auodesh@yahoo.com, sunit_gupta@rediffmail.com
Tel: 06782-272103, 06782-272032, Fax: 06782-272170


Abstract
As a technology Global positioning system (GPS) has got a vital role in Test Range applications. Flight vehicle Test Range is set up for performance evaluation of Rockets, Missiles and other airborne vehicles. For the flight evaluation of any test object, it’s time and space position information plays a crucial role in determining its performance against pre-determined trajectory parameters. In this regard, Test Range has got a prime role in providing the accurate time and space position information data to the designers/users. Thus requires an accurate calibration source for tracking instrument. As performance of various test vehicles are evaluated presently using various tracking instrumentation systems like optical/Infrared, Radar, Telemetry DGPS (Differential Global Positioning System) has a prime role in calibrating these trackers.

To fulfill the above objective, Range validation helicopter/ aircraft sortie has been conducted in Test Range. During sortie, all the tracking sensors deployed at various sites tracks the target. At the same time rover GPS receiver set installed in helicopter/ aircraft (i.e. on board) also provides positional information of helicopter/aircraft. The GPS reference station is installed at precisely surveyed benchmark location. In real time RTCM corrections are transmitted from reference station to rover station by UHF transreceiver communication antenna installed at reference station. The same antenna is receiving the rover station positional information from helicopter. The positional information derived from GPS along with the other tracking sensors has been displayed. Sortie controller identifies GPS and other tracking sensor position using different color displays. For real time display, a GPS data Acquisition and display software has been developed in VC++ environment.

The basic function of this software is enumerated below:
  • To obtain the rover GPS station positional information at reference station.
  • Conversion and display of this position values (in latitude, longitude, altitude) in chosen reference co-ordinate point to easting (X) and northing (Y) coordinate system with earth curvature correction.
  • Transmission of rover GPS position to central computer through e-net for real time plotting with other tracking sensor. So that sortie controller can observe the tracking status of each tracking instruments and the difference of other tracking instruments w r t GPS.
  • Compilation of bias of tracking sensor with respect to DGPS source.
This software has interactive user-friendly interface for initialization is reference station location, COM port setting like baud rate, COM port number and file name for rover positional data logging etc. it also has the provision of changing reference station in real time. It mainly contains four functional blocks:
  1. Data acquisition block
    Data acquisition from rover station has been done in real time through COM port. Time division multiple accesses (TDMA) setting in GPS reference receiver is very important in this context. Data input to this block is receiver identification number, date, GPS time, position in latitude, longitude, mean sea level (MSL) height w r t WGS84 datum, operating mode, horizontal accuracy, speed and best five satellites.
  2. Data processing and storage block.
    The input rover positional data format is latitude, longitude and MSL height. In order to make compatible with other tracking sensor format for display and comparison purpose, it is converted into easting (X) and northing (Y) coordinate with respect to some reference point by applying suitable earth curvature correction. The converted data is then stored in user-defined file.
  3. Data display and real time plot block.
    Rover GPS position is plotted in real time w r t suitable reference point location at GPS reference station. Alphanumeric display of some important parameter is shown in graphic window like GPS time, latitude, longitude, MSL height, X and Y with respect to reference point.
  4. Data transfer block.
    The converted data is then transmitted to central computer for real time plotting along with other tracking sensors. Time synchronization of all tracking sensor with GPS time is very crucial step in this process. For redundancy purpose to sortie controller, DGPS data can be plotted at reference station computer and central computer along with other tracking sensor positional state vector data. In future for multi target scenario, the software can be enhanced for multi target identification. GPS receiver at reference and rover station can be set to become compatible with multi target scenario by using TDMA techniques.

    This paper mainly covers the application of this software to Integrated Test Range and it’s configuration for single and futuristic multi target scenario. This paper also covers few typical kinematic tracking application and display of DGPS data for accurate bias estimation of Range tracking instruments, along with futuristic Range application.