MULTIRESOLUTION SPOT-5 DATA FOR BOREAL FOREST MONITORING
M. G. Rosengren, E. Willen
Metria Miljöanalys, P.O. Box 24154, SE-104 51 Stockholm, Sweden - (mats.rosengren, erik.willen)@lm.se
KEY WORDS: Remote Sensing, Forestry, Change Detection, Classification, Fusion, Satellite, Multiresolution, Optical
ABSTRACT:
The improved spatial resolution of SPOT-S data opens for improved forestry applications, such as improved cutting delineation,
identification of soil scarification activities and for monitoring of the establishment of new forest stands. The large scene size
combined with very high resolution is an operational strength when compared to VHR satellite data, although there are operational
limitations for very large area coverage. Since 1999, the Swedish National Board of Forestry (NBF) has extensively used satellite
data from Landsat TM, ETM+ and SPOT in its operational work. Satellite data is used for change detection analysis, primarily to
map and monitor forest cuttings as required in the Swedish Forestry Act and for mapping areas of different forestry activity needs.
User adapted methods for change detection and analysis were developed and implemented by Metria in the ENFORMA tool, now
used operationally at the 100 forestry districts of Sweden. Yearly national satellite data coverages of Sweden, from SPOT-4 and
Landsat-7 ETM are acquired by NBF and operationally used in the daily work. In 2003, a national coverage with SPOT-5 10 m
multispectral data was ordered with 150 SPOT-5 and 50 SPOT-4 delivered. This study has focused on evaluating the improved data
quality from SPOT-5 in comparison and in combination with SPOT-4 and Landsat-7 data, for information concerning forest cuttings
and factors of importance for the establishment of new forest stands by using multiresolution satellite data. Methods for enhanced
change detection with combined use of the different resolutions of SPOT-5 multispectral bands were tested. Multiresolution, single
band change detection between image pairs with pixel size differences of 2.5 — 30 m was evaluated. A method for multiresolution
merging of panchromatic with all multispectral bands including SWIR applicable for boreal forestry was tested for this purpose.
Examples from the use of SPOT-5 data for operational and recurrent national (Sweden) coverage are given.
1. INTRODUCTION
With the improved spatial resolution of SPOT-5 data (red,
green and NIR —10 m, SWIR — 20 m and Pan - 5 and 2.5 m),
new and improved forestry applications open up. SPOT-5 data
can provide better information for improved cutting delineation,
identification of soil scarification activities and for monitoring
of the establishment of new forest stands. The introduction of
SPOT-5 data, combining very high resolution with large scenes,
is also of great importance for large area coverage, although
there are operational limitations. SPOT data has also
historically proven to have excellent geometric and radiometric
quality, simplifying the use of the data.
Since 1999, satellite data from Landsat TM, ETM+ and SPOT
have been extensively used by the Swedish National Board of
Forestry (NBF) in its operational work.. The satellite data is
used for change detection analysis, primarily to map and
monitor forest cuttings as required in the Swedish Forestry Act
and for mapping areas of different forestry activity needs.
For this purpose, user adapted methods for change detection
and analysis were developed and implemented by Metria in the
ENFORMA tool, in response to the user requirements of NBF.
National satellite data coverages of Sweden, from SPOT-4 XI
(1999) and Landsat-7 ETM- (2000, 2001, 2002) have been
acquired by NBF and are now used operationally in the daily
work at the 100 forestry districts of Sweden. The total land area
of Sweden is 450.000 km”. In 2003, a national coverage with
SPOT-5 10 m multispectral data was ordered and approximately
150 SPOT-5 scenes supplemented by some 50 SPOT-4 XI
scenes were delivered.
This study, selected by the French Space Agency, CNES and
Spotlmage to be part of the SPOT 5 Application Valorization
Program (SAVP), has focused on evaluating the improved data
quality from SPOT-5 in comparison and in combination with
SPOT-4 and Landsat-7 data, for new and enhanced information
concerning forest cuttings and factors of importance for the
establishment of new forest stands by using multiresolution
satellite data. Change detection methods between 20 and 30 m
resolution data are already proven and are used operationally on
older datasets including Landsat-5 TM and SPOT 1-4 data.
These methods can be further developed for better, combined
use of the different resolutions of SPOT-5 multispectral bands.
Multiresolution, single band change detection between image
pairs with pixel size differences of 2.5 — 30 m was evaluated.
Methods for enhanced change detection were also examined.
Better and more cost-effective data for visual interpretation is
also an important and potentially widespread application for
SPOT-5 data in addition to advanced image processing
methods.
A method for multiresolution merging of panchromatic with all
multispectral bands including SWIR applicable for boreal
forestry was tested for this purpose.
2. STUDY AREA AND DATA
2.1 Study area
The study area, Figure 1, is situated in the southern part of
Sweden in the forestry district of Nässjö. It has been used for
several years for development of different forestry applications
from SPOT and Landsat TM data. The forest of this part of
Sweden is owned by numerous private owners and the average
size of the mapped clear cuts is between 1:5 and 2 hectares.
Examples of applications tested in cooperation with NBF in the
Nässjô district are refined clear cut mapping, mapping of seed
trees left on felled areas, identification of regeneration activities
such as soil scarification and also detection of regeneration
failures.
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