3. Istanbul 2004
THREE-DIMENSIONAL MAPPING WITH AIRBORNE IFSAR BASED
STAR TECHNOLOGY — INTERMAP'S EXPERIENCES
X. Li, K. Tennant, G. Lawrence
Intermap Technologies Corp., 2 Gurdwara Road, Suite 200, Nepean, Ontario, Canada K2E 1A2
(xli, ktennant, glawrence)()intermaptechnologies.com
Commission III, WG III/3
KEYWORDS: High resolution, Interferometer, SAR, Mapping, DEM/DTM, Orthoimage
ABSTRACT:
Airborne Interferometric Synthetic Aperture Radar (IFSAR or INSAR) is maturing as a cost-effective three-dimensional mapping
technology. It is attracting increased attention in the geospatial community because of its unique operational advantages. Various
mapping products are being generated by Intermap’s STAR technology which is based on high-resolution airborne IFSAR. More
significantly, these STAR derived products are being used for applications traditionally supported by other mapping technologies
and this list of applications is growing. This trend is due to the ever-increasing customer confidence towards the STAR derived data.
Involved with IFSAR technology since 1993, Intermap is diligently working to exploit the potential of this technology and to
develop new, market specific applications. To reach a more widespread acceptance and a deeper and wider application base,
Intermap's STAR technology and its mapping products are continuously presented to the general geospatial public from the early
adopters through the general provider. Experiences obtained from those applications are highly beneficial to potential users. The
objective of this paper is to give the reader a general picture of airborne IFSAR mapping in order for them to better understand the
strengths and limitations of the technology and the products.
1. INTRODUCTION
There is a growing demand for high-quality and low-cost three-
dimensional (3-D) mapping data for many geospatial
applications. Recent advances in sensor development and geo-
referencing technologies, coupled with the continuous
improvement of digital computing power now enable
unparalleled functionality and flexibility in geospatial mapping.
Currently, several technologies are being used to generate map
products at various scales, details and accuracy, with strengths
and limitations associated with each technology. Leaders in the
geospatial community are gradually realizing that airborne
Interferometric Synthetic Aperture Radar (IFSAR or INSAR) is
maturing as a complementary or competitive cost-effective 3-D
mapping technology, evidenced by the several ongoing nation-
wide airborne IFSAR mapping efforts.
IFSAR attracted much attention in the geospatial community
since data became widely available from the microwave sensor
on the ERS-1 satellite. Also, the Shuttle Radar Topographic
Mission (SRTM) that flew successfully in February 2000
provided a further impetus for mapping applications using
IFSAR technologies. Advantages associated with airborne
IFSAR mapping include flexibility of system deployment, near
weather-independent operation, cloud penetrating capability,
versatile map products, and quick turn-around time.
Three-dimensional mapping products generated by Intermap's
STAR technology based on high-resolution airborne IFSAR are
being used for applications traditionally supported by other
mapping technologies. The product family consists mainly of
digital surface models, digital terrain models, and orthorectified
radar imagery. In addition, other value added products such as
topographic line maps, colorized radar images, and fly-through
are produced. The list of applications for these products is
growing continuously due to the appropriateness of the data and
the ever-increasing client confidence towards them.
The objective of this paper is to give the reader a general
picture of STAR technology and its mapping products in order
for them to better understand the strengths and limitations of
the technology employed to collect and process the data. In the
paper, after a brief introduction to IFSAR technology and
operating principles, typical mapping mission implementation
is outlined. Generation of STAR technology based mapping
products is described. Conclusions and the future of airborne
IFSAR mapping are given at the end of the paper.
24. AIRBORNE IFSAR TECHNOLOGY
— IMPLEMENTATIONS, ADVANTAGES AND
LIMITATIONS
Enabled by cost-effective sensor positioning and orientation
solution using Global Positioning System (GPS) and Inertial
Navigation System (INS) technologies, airborne IFSAR
technology is being used as an accurate and reliable 3-D
mapping tool. In the early 1970s, airborne IFSAR was applied
for topographic mapping studies. Nevertheless, the first
commercial airborne IFSAR system entered the mapping world
in 1996 — Intermap's STAR-3i®. Since then, considerable
efforts have been applied and many lessons have been learned
on the road to commercializing the STAR IFSAR systems
(Tennant and Coyne, 1999; Tennant et al, 2003). As a result,
the STAR technology has become more robust and practical,
generating mapping products for end users faster and better.
2.1 Single-pass and Dual-pass Mode
Radar interferometry for topographic mapping needs to
coherently combine microwave signals collected from two
