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STAR-2 System 
INTERA’s second STAR system, STAR-2, was designed as an 
improved version of STAR-1, and built in Canada in 1986. It was 
operated in a Cessna Conquest for two years for both sea ice 
monitoring and terrain mapping (particularly topographic map 
ping using the STARMAP process), after which it was decom 
missioned, twinned and recommissioned in a Challenger jet 
aircraft under contract to the Atmospheric Environment Service 
(AES) of Environment Canada (Mercer 1989). Since 1989, this 
dual-sided STAR-2 system has been operating (as CANICE-5) in 
the Canadian Arctic as part of the AES ice information service, 
providing real-time ice monitoring information to the Canadian 
Coast Guard icebreaker fleet, drill rigs and ships, vessels in 
volved in Arctic transportation, etc. This system also operates in 
two formats: standard resolution (4x 16m, with 63 km swath) and 
high resolution (4x6m, with 16 km swath), both with simultane 
ous dual viewing directions. Data are recorded on cassette tape 
onboard the aircraft, and may also be downlinked in real-time to 
any of nine vessels with receiving stations (receiver plus STAR- 
VUE display system). The system can acquire 150.000 square 
km per hour of image data. 
STARMAP Topographic Mapping 
STAR-1 application development initially concentrated on the 
thematic rather than the cartographic features of the radar data. 
However, with an increasing desire for improved geometric 
fidelity in the digital output of the radar, a series of developments 
culminating in STARMAP (INTERA’s name for the process of 
creating topographical mapping products from STAR-1 im 
agery) have taken place. 
Originally, the fundamental STAR product was film strips that 
could be used individually, in stereo pairs, or assembled into ‘lay- 
down’ mosaics. Using “good” (i.e., accurate) maps for control, 
the strip products could be scaled to about 1% accuracy. In the 
absence of such base maps, however, the errors inherent in the 
aircraft INS (Inertial Navigation System) were reflected in coor 
dinate errors of hundreds of meters in strip or mosaic products. 
Moreover, terrain displacement effects (inherent in radar data) 
produced additional errors proportional to the terrain relief in the 
imaged area. 
In 1987 Intera implemented a digital mosaicking process, utiliz 
ing a modified Dipix ARIES III image analysis system (Schultz 
et al. 1989). Large numbers of control points, when available, 
could be used in the image-to-map registration process, radio- 
metric corrections were applied digitally, seams were hidden, 
and the output product was digital. Using a fine resolution large- 
format plotter, high quality film products were created, thereby 
preserving resolution and retaining more information than in the 
previous mosaicking method. 
Since 1989, INTERA has been recording the STAR-1 flight path 
using GPS (Global Positioning System) (Mercer et al. 1989). 
Together with a model of the radar system, a set of ‘virtual’ 
GCP’s are computed for study areas where base maps or other 
forms of control are lacking, and used in the digital mosaicking 
process. Typical uncertainties are of the order of 100-200m RMS 
in moderately flat terrain, and terrain displacement effects are not 
removed. 
In the STARMAP process, elevation data are extracted from 
STAR stereo pairs to create DEM’s (Digital Elevation Models) 
and contours (Figure 1), to correct for terrain displacement in the 
imagery, and to create geocoded image maps at scales of 
1:50.000 to 1:100.000 (Merceretal. 1987;Leberl 1989). Differ 
ential GPS is now a part of the process; planimetric errors are 
<25m RMS while vertical errors are slightly larger (Mercer et al. 
1989). 
STAR System Areal Coverage 
Table 1 summarizes the area flown by the STAR systems since 
1983, by type of program and region of the world. 
Table 1. STAR System World Coverage (thousand square km) 
since 1983, by Program Type and Region. 
Program 
Type 
North South 
America America* 
Asia 
Other 
TOTAL 
Ice 
Monitoring 
78,000 
— 
— 
1,210 
79,210 
Forestry 
15 
17 
70 
45 
117 
Agriculture/ 12 
Soil/Land Use 
7 
800 
15 
834 
Geology 
1,500 
205 
805 
62 
2,572 
Topographic 
Mapping 
30 
570 
30 
— 
630 
TOTAL 
79,557 
799 
1,705 
1,332 
83,363 
* Includes Central America 
Ice monitoring in North America has accounted for 95% of the 
STAR data acquisition to date, due to its regular, repetitive cov 
erage requirement over large areas of the Arctic. The STAR-2 
system alone has accounted for 32 million square km of data 
acquisition in six months. The second largest type of radar 
program is related to geological mapping and exploration, and 
this need is well distributed worldwide. The resource manage 
ment programs involving forestry, agriculture, land use and soil 
mapping and monitoring have mainly been carried out in 
southeast Asia (90%), where SAR data are used to provide good 
information in areas with persistent cloud cover. Topographic 
mapping, a much more recent development, has been carried out 
in nearly all regions, with the majority (90%) in South America 
to date. Again, this application has been used to provide base 
planimetric and topographic information predominantly in areas 
with persistent cloud cover. 
ENVIRONMENTAL STUDIES USING STAR DATA 
The following describes several types of environment-related 
programs which have been completed using STAR system 
data.