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Figure 2 - INS Simulation Teaching Tool Screen Shot 
2.3 IESSG's GPS/IMU Simulator 
Over the last 15 years the IESSG has independently developed 
a GNSS simulator that enables measurements to be generated 
and procedures and capabilities to be assessed. This has 
provided research opportunities that would not otherwise have 
been available. 
  
  
  
  
  
  
  
  
  
  
  
  
      
  
  
  
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Figure 3 - Schematic of the GNSS data simulation process 
More recently the GNSS simulator has been expanded to 
include the capability to simulate Inertial Measurement Unit 
(IMU) components (gyros, accelerometers) in an integrated 
environment. Detailed models of the performance of the inertial 
components have been developed, so that synthetic GNSS data 
and IMU data can be produced from a common platform. A 
trajectory generator allows synthetic data to be produced from a 
combined GNSS/IMU platform that is moving in a precisely 
controlled way. Data from this tool has been validated using an 
analysis filter from another source, as well as with in-house 
analysis tools. 
To date, these two tools have been used in a number of internal 
and contract research projects as well as being developed as a 
teaching tool. Of note is their use to simulate and assess the 
performance of future low-cost inertial components in an ESA- 
funded project entitled the 'Low-Cost Navigator. They have 
also been used to develop an adaptive Kalman Filter, which 
integrates measurement data from GPS and inertial navigation 
sensor data. The aim of the filter is to optimise the blend of 
these two distinctly different types of measurements and make 
the best use of the synergy between them, to provide precise 
and reliable positioning. 
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Für. Options 
DOP Results Viewer 
  
Store 
  
Save 
  
Results menu 
  
  
  
  
  
  
  
Current Data: Constellation - GPS + Gal, Elevation mask - 25 deg, 
Start Time - 12:00, Duration - 6 hours 
Time Step - 10 min., Grid Spacing - 10 x 10 deg 
The information has been stored for later viewing, 
  
Figure 4 — IESSG's Navigation Performance Tool 
Recognising the strengths of the filter design, including its 
ability to work in a centralised or de-centralised mode, its 
ability to process carrier phase data, and its adaptive 
capabilities, the IESSG has recently begun a programme of 
development to produce a commercial version of the filter, 
suitable for embedding in bespoke hardware designs. 
Developed as a research tool, the simulator has also provided 
the IESSG with a powerful teaching tool. The rapid generation 
of data and the graphical representation of the results enables 
students to understand the principles and gain experience of 
results when parameters are changed. 
© raim s i Tx] 
Fie Options 
RAIM Availability Results 
  
  
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View Graph B 
  
  
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900 -.950 
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Current Data; Constellation - GPS, 
i UERE - 8.0m, 
Phase - Nonprecision, Mask Angle - 15 deg, Start Time - 07:00, 
Duration - 1 hour, Time Step - 2.5min., Grid Spacing- 10x 10 deg 
  
Figure 5 - IESSG's RAIM Analysis Tool 
2 IESSG's Aerial Triangulation Simulator - SIMAT2 
2.1 Background 
SIMAT2 is a research program that simulates all the data 
required to complete an aerial triangulation including: 
— A Ground Control Points 
— Photo Points 
- In-flight GPS 
— In-flight IMU 
The user can define all relevant parameters at run time 
including: 
— Number of photos