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International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B1. Istanbul 2004 
  
So, apart from HW/SW configuration a great effort has to be 
put into the understanding of the sensors and their calibration, 
before good results can be obtained. 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
Systron iMAR Northrop — |iMAR 
Mark Donner Navigation |Grumman Navigation 
Motion Pak iNAV-F JI- 
Model Il iVRU-SSK |LN-200 IDEG-001 
Gyro 
Bias 5 °/sec <3 °/sec hr 0.003 °/hr 
SF (ppm) 60000 <10000 100 < 30 
Noise (%/Vhr)-RW _|12 <3 0.07 < 0.001 
Accel 
Bias (ug) 200000 «200000 [300 <5 
SF (ppm) 50000 <50000 300 < 60 
Noise (ug/VHz) 700 <800 50 8 
Interface RS232 CAN-BUS |HDLC Ethernet 
Data Rate (Hz) 32 200 400 1500 
Synchro signals NO YES YES YES 
12.8.x 112 20 x 20 x 
Size (cm) x 116 8x8»x12 |89 0 x85 20 
Weight (kg) 1.2 <1 0.8 5.5 
Performance 
P.R (deg — RMS)  |«0.5(*) «0.1(*) 0.02 «0.01(*) 
H (deg - RMS) <1(*) <0.5(*) 0.01 <0.01(*) 
Cost (€) 2000 10000 20000 >100000 
(*) These figures are estimations. 
  
Tab.1 — Properties of the four IMUs of the IG 
In the following the IG IMUs are listed: 
3.7.1 Systronner Donner MPK2 
This inertial low cost measurement unit contains six "solid- 
state" micro electro mechanical system (MEMS) sensors. It has 
3 
3 micromachined quartz angular rate sensors (QRS) and 3 
silicon (Si) accelerometers. 
3.7.2 iMAR Navigation iVRU-SSK. 
This is also a low cost unit that fills the gap between the MPK2 
and the LN200. It is intended to be used for real time 
applications and stabilization, but it is also being considered to 
be used for direct georeferencing. Its sensors are also based on 
MEMS technology. The IG has collaborated with the 
manufacturer, iMAR Navigation, in its design. So, the 
instrument reflects the experiences made at both entities. 
3.7.5 Northrop Grumman LN-200 
This tactical grade inertial measurememt unit has ortogonally 
m 
mounted 3 fiber optic FO gyros and 3 silicon (Si) 
accelerometers. 
The device is commonly used in photogrametry applications, 
remote sensing surveys and frequently is one of the components 
in commercial navigation systems. 
3.74 | iMAR Navigation iNAV-FJI-IDEG-001. 
This navigation grade IMU is the top device of the IG. The 
sensor is composed of high quality fibre optic (FO) gyros and 
quartz flexure (QFLEX) accelerometers. Its features will make 
this instrument a reference device for all purposes. Thanks to 
the collaboration with the manufacturer in its design, it is made 
to measure after IG specifications. 
3.8 Next development steps 
As was mentioned before, the TAG is a system that is 
continuously evolving. So, new developments that are based on 
the TAG are being prepared: 
e The integration of a solid — state and rug 
disk that will make the system suitable for utilization 
in harsh environments. 
e The development of a “mini — TAG” to reduce the 
current size and weight of the system. 
e The migration to LINUX OS with RT core for 
enhanced real-time capacities. 
gedized hard 
4 EXPERIMENTS AND RESULTS 
The TAG has been used in a series of experiments and tests. By 
april 2004, the TAG has accumulated 18 flight-hours and 
numerous car and laboratory tests. In the following, a small 
summary of those experiments is given. 
4.1 SR-IMU experiment. 
One of these experiments is related with the current research on 
skewed redundant IMUs (SR-IMU), that the IG is carrying out 
[Colomina et. Al, 2003 and Colomina et al. 2004]. The TAG 
was used to acquire the LN-200 raw data in a flight combined 
with another LN-200 in a non orthogonal configuration as if 
they were a redundant IMU. The results of this flight showed 
that the measurement made by the 2 IMUs were consistent and 
are good enough to use them in further research for the SR- 
IMUs. 
RENI 
HAI. 
  
Fig.3 — TAG installation for skewed redundant configuration. 
4.2 Van test. 
Recently a test of the performance of the real time mode of 
TAG for a land vehicle was conducted. The test consisted of a 
route of about 1h near the city of Castelldefels (Barcelona - 
Spain). The trajectory was calculated in real time processing 
and raw data was stored for post-processing. The trajectory can 
be seen in the figures 6 and 7. Figure 7 is a zoom of figure 6 in 
which it can be seen the difference between the real time 
solution and the post-processed solution. 
The TAG system and the batteries (Fig.4) were installed at the 
boot of the vehicle. All the devices were carefully fixed to its 
surface. 
The IMU Bench platform with the LN-200 mounted on it, was 
placed at the back of the driver seat on the floor and properly 
fixed (Fig.5).