GUEST POST: A Very Brief History of Optical High Resolution Satellite Imaging

The history of the optical high resolution satellite images starts from classified military satellite systems of the United States of America that captured earth’s surface from 1960 to 1972. All these images were declassified by Executive Order 12951 in 1995 and made publically available (Now freely available through the USGS EarthExplorer data platform under the category of declassified data). From 1999 onward, commercial multispectral and panchromatic datasets have been available for public. Launch of Keyhole Earthviewer in 2001, later renamed as Google Earth in 2005, opened a new avenue for the layman to visualize earth features through optical high resolution satellite images.

A comparison of declassified Corona (1974) vs. GeoEye-1 (2014) image. Image credits: EarthExplorer (Corona) and Google Earth (GeoEye-1).

In the current era, most high resolution satellite images are commercially available, and are being used as a substitute to aerial photographs. The launch of SPOT, IKONOS, QuickBird, OrbView, GeoEye, WorldView, KOMPSAT etc. offer data at fine resolutions in digital format to produce maps in much simpler, cost effective and efficient manner in terms of mathematical modeling. A number of meaningful products are being derived from high resolution datasets, e.g., extraction of high resolution Digital Elevation Models (DEMs) with 3D building models, detailed change assessments of land cover and land use, habitat suitability, biophysical parameters of trees, detailed assessments of pre and post-disaster conditions, among others.

Both aerial photographs and high resolution images are subject to weather conditions but satellites offer the advantage of repeatedly capturing same areas on a reliable basis by considering the user demand without being restricted by considering borders and logistics, as compared to aerial survey.

Pansharpening / resolution merge provides improved visualization and is also used for detecting certain features in a better manner. Pansharpening / resolution merge is a fusion process of co-georegistered panchromatic (high resolution) and multispectral (comparatively lower resolution) satellite data to produce high-resolution color multispectral image. In high resolution satellite data, the spectral resolution is being increased and more such sensors with enhanced spectral sensitivity are being planned in the future.

List of the Spaceborne Sensors with <5 m Spatial Resolution

Sensors	Agency/Country	Launch Date	Platform altitude (km)	GSD Pan/MSS (m)	Pointing capability (o)	Swath width at nadir (km)
IKONOS-2	GeoEye Inc./USA	1999	681	0.82/3.2	Free View	11.3
EROS A1	ImageSat Int./Cyprus (Israel)	2000	480	1.8	Free View	12.6
QuickBird	DigitalGlobe/USA	2001	450	0.61/2.44 Pan and MSS alternative	Free View	16.5
HRS	SPOT Image/France	2002	830	5X10	Forward/left +20/-20	120
HRG	SPOT Image/France	2002	830	5(2.5)x10	sideways up to ±27	60
OrbViw-3	GeoEye Inc./USA	2003	470	1/4	Free View	8
FORMOSAT 2	NSPO/China, Taiwan	2004	890	2/8	Free View	24
PAN (Cartosat-1)	ISRO/India	2005	613	2.5	Forward/aft 26/5 Free view to side up to 23	27
TopSat Telescope	BNSC/UK	2005	686	2.8/5.6	Free View	15/10
PRISM	JAXA/Japan	2005	699	2.5	Forward/Nadir/aft -24/0/+24 Free view to side	70 35 (Triplet stereo observations
PAN(BJ-1)	NRSCC (CAST)/China	2005	686	4/32	Free View	24/640
EROS B	ImageSat Int./Cyprus (Israel)	2006	508	0.7/-	Free View	7
Geoton-L1Resurs-DK1	Roscosmos/Russia	2006	330-585	1/3 for h = 330km	Free View	30 for h = 330km
KOMPSAT-2	KARI/South Korea	2006	685	1/4	sideways up to ±30	15 km
CBERS-2B	CNSA/INPE China/Brazil	2007	778	2.4/20	Free View	27/113
WorldView-1	DigitalGlobe/USA	2007	494	0.45/-	Free View	17.6
THEOS	GISTDA/Thailand	2008	822	2/15	Free View	22/90
AlSat-2	Algeria	2008	680	2.5	up to 30 cross track Free view	17.5
GeoEye-1	GeoEye Inc./USA	2008	681	0.41/1.65	Free View	15.2
WorldView-2	DigitalGlobe/USA	2009	770	0.45/1.8	Free View	16.4
PAN (Cartosat-2, 2A, 2B)	ISRO/India	Cartosat 2-2007 Cartosat 2A-2008 Cartosat   2B-2010	631	0.82/-	Free View	9.6
KOMPSAT-3	KARI/South Korea	2012	685	0.7/2.8	±45º into any direction (cross-track or along-track)	15
WorldView-3	DigitalGlobe/USA	2014	617	0.3/1.24/3.7/30		13.1

 Conflicts of Interest: The findings reported stand as scientific study and observations of the author and do not necessarily reflect as the views of author’s organizations.

 About this post: This is a guest post by Hammad Gilani. Learn more about this blog’s authors here.