ACCURACY ASSESSMENT OF VEGETATION MONITORING
WITH HIGH SPATIAL RESOLUTION SATELLITE IMAGERY
RAFAEL WIEMKER, BORIS PRINZ, GERHARD MEISTER, RAMON FRANCK, HARTWIG SPITZER
II. Institut für Experimentalphysik, CENSIS
Universität Hamburg
Mail: KOGS, Vogt-Kölln-Str. 30, 22527 Hamburg, Germany
WWW: http://kogs-www.informatik.uni-hamburg.de/projects/Censis.html
(wiemker,prinz,meister,franck ) Gkogs.informatik.uni-hamburg.de
KEY WORDS: Data Fusion, Multispectral Image Sharpening, High Resolution Satellites, Classification Accuracy
ABSTRACT
For the years 1997 to 2000 it is expected that a number of new satellites will be launched into orbit by private
companies which are specified to deliver panchromatic imagery of the earth surface with a spatial resolution as fine
as 1m. In contrast to the panchromatic band, the spectrally resolved bands will have a four times coarser ground
resolution. Therefore, image fusion algorithms will be employed in order to produce panchromatic-‘sharpened’ color
imagery.
The new satellites have the potential of stimulating and expanding the remote sensing market for image products at a
resolution around one meter. In order to prepare for this era we have examined image fusion algorithms using already
available airborne imagery. This paper describes tests of fusion algorithms on imagery which was simulated using
multispectral images of an airborne scanner (DAEDALUS ATM) with an average pixel size of 1 m. The main advantage
of this simulation of satellite images is the possibility to measure quantitatively the accuracy of the panchromatic-
sharpened multispectral imagery. By comparison with the original airborne imagery, we evaluate the accuracy of
the sharpened imagery with respect to the spectral signature, NDVI, local variance, and multispectral land cover
classification.
1 HIGH RESOLUTION SATELLITE IMAGERY FOR
LOCAL ENVIRONMENTAL MONITORING
For the years 1997 to 2000 it is expected that a number
of new satellites will be launched into orbit by private
companies (Doyle 1996, Fritz 1997) which are specified
to deliver imagery of the earth surface of a spatial reso-
lution as fine as 1 m.
This fine a resolution has so far been the privilege of
airborne rather than spaceborne overhead imagery — at
least as far as the civilian community and multispectral
(in contrast to panchromatic) imagery is concerned. Air-
borne image flights have a longstanding importance for
cadastre, local planning and local environmental moni-
toring (e.g. the health status of public trees in the city
of Hamburg is monitored on aerial Color Infrared (CIR)
photographs). So far the necessary image flights are con-
ducted mostly by private enterprises on particular cus-
tomer request. They are thus rather expensive.
Multispectral spaceborne imagery on the other hand
has been exploited for a number of environmental is-
sues (such as deforestation, desertification, plant stress,
water polution, climate warming etc.) but always on
a global or regional scale — due to its limited spatial
resolution (LANDSAT TM images have a pixel size of
30 x 30 m).
With the arrival of meter-range spaceborne imagery
which can be purchased off-the-shelf by local authori-
ties at the instance when the demand arises, overhead
imagery may become a serious option even for purposes
of local interest which up to now could not justify the
higher cost of a dedicated image flight.
2 SIMULATION OF HIGH RESOLUTION SATELLITE
IMAGERY FROM MULTISPECTRAL AIRBORNE
SCANNER IMAGERY
First image-recording of the announced satellites is ex-
pected for 1998. It can be assumed that the testing and
calibration phase will last for the first year of operation.
It has to be noted, however, that the schedule for all of
the announced satellites already had to be delayed sev-
eral times.
In the meantime, we are in the position to simulate the
high resolution satellite imagery from airborne scanner
images of comparable spatial resolution. The imagery
was recorded by a DAEDALUS ATM line scanner with
10 spectral bands on board a Dornier Do 228 aircraft
during five campaigns from 1991 to 1997 in coopera-
tion with the German Aerospace Center (DLR WeBling /
München) at flight altitudes of 300 m, 900 m and 1800 m.
The 300m imagery has a nadir-looking ground resolu-
tion of 70cm. Due to the panorama characteristic of so-
International Archives of Photogrammetry and Remote Sensing. Vol. XXXII, Part 7, Budapest, 1998 285
