The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B5. Beijing 2008 
2.2.2 Time savings: Figure 16 shows an enlargement of one 
of the flight trajectories, colour coded by roll angle. In this case 
green indicates a roll of less than 10 deg, yellow is between 10 
to 20 deg, orange is from 20 to 25 deg, red is from 25 to 30 deg, 
and grey is above 30 deg. The plot clearly shows that the larger 
the bank angle, the tighter the turn, and the faster the aircraft is 
back on line. 
Table 2 is a summary of the average turn times for the flights. 
The turn times are defined as the time between the last photo in 
a line and the first photo in the next line. The percent 
improvement is computed with respect to the flight having a 
maximum bank angle of 25 deg with 170 sec average turn time. 
# 
Max Roll 
(deg) 
Avg Spd 
(knot) 
Avg Turn 
(sec) 
% 
Improvemen 
t 
1 
25 
105 
170 
n/a 
2 
25 
97 
150 
n/a 
3 
40 
97 
110 
35 
4 
30 
97 
120 
29 
5 
40 
116 
110 
35 
6 
30 
116 
140 
18 
7 
30 
116 
130 
24 
8 
35 
127 
120 
29 
Avg 
28 
Table 2. Summary of Average Turn Times 
The results show that simply by increasing the bank angle from 
25 deg to 30 to 40 deg, the time to fly the turns was reduced by 
an average of 28%. Using the average time to turn of 170 
seconds for the 25 deg bank angle flight, this translates to an 
average savings of 48 seconds per turn. With an average of 12 
turns per flight, and an average of 50 flights per year, this 
translates to a savings in flight time of 12x44x48 = 28,800 
seconds or 8 hours. Such a savings could easily be doubled or 
tripled for standard survey missions that have many more turns 
than a DSS flight test, especially if the turns are being flown at 
a bank angle less than 25 deg (say at 15 to 20 deg). 
3. CONCLUSIONS 
The new Applanix SmartBase and IN-Fusion technology 
implemented in the POSPac MMS software represents a 
paradigm shift in operational efficiency for aerial mapping: 
• It can produce the same position accuracy as standard 
differential GPS with a dedicated reference station, 
but without the restriction of having to always fly less 
than 75 km from a reference station 
• It can solve for the correct integer ambiguities 
without the need to fly within 30 km or less of a 
reference station 
• It can eliminate the need to fly flat turns, which 
reduces the time to fly a mission, enables more 
flexible mission execution in restricted airspace, and 
reduces crew fatigue leading to fewer mistakes and 
increased safety. 
Future work will focus on clearly defining the requirements for 
reference station location, density, and data quality in order to 
reliably and robustly meet the performance claims, especially 
during periods of increased ionosphere activity. 
As a final note, performance results are only expected to 
improve as additional GNSS observables are added to the 
processing. 
ACKNOWLEDGEMENTS 
The authors would like to thank the entire POSPac Air team for 
the months of blood, sweat and tears they have put into this 
development. Thanks are also given to J.P. Barrier from 
Track’air for his useful input on optimal aircraft bank angles for 
survey missions. 
REFERENCES 
Hakli P., 2004, Practical Test on Accuracy and Usability of 
Virtual Reference Station Method in Finland, FIG Working 
Week 2004, Athens, Greece 
Hutton J., Bourke, T., Scherzinger, B., 2007, New 
Developments of Inertial Navigation Systems at Applanix, 
Photogrammetric Week 2007 
Landau H., Vollath U., and Chen X., 2002, Virtual Reference 
Station Systems, Journal of Global Positioning Systems, Vol. 1, 
No. 2, 2002 
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