Transcript Slide 1

Change analysis of Northborough, Massachusetts, 1987-2001
Kristopher Kuzera and Silvia Petrova
Objective
Study area
The objective is to compare land cover change in Northborough, Massachusetts using the images from the
Landsat Thematic Mapper (TM) satellite from September 10, 1987 and ASTER satellite from August 29, 2001.
Land cover classification based on spectral classes has been performed and reclassified into information
classes. Change analysis has been done at 30 meter resolution for both the TM and ASTER images.
Normalized Differences Vegetation Indexes (NDVI) have been created to compare biomass levels and change
in vegetation over the 14 year period.
Northborough, located in central Massachusetts, has a population of
14,013 from the year 2000. The town has experienced enormous amounts
of land cover change in recent decades due to the continuing expansion
of the Greater Boston metropolitan area, as well as the introduction of the
electronics industry into the region, making it a good candidate for land
cover change analysis.
1987 LANDSAT TM – 30m resolution
Prior Knowledge Land Cover Maps
False Color Composite Bands 2,3,4
Band 2 GREEN
Band 3 RED
Tools
All analysis was performed
using IDRISI Kilimanjaro.
Land Cover Classification
1987
Land Cover Change Comparison
(Landsat TM '87 30m resolution vs. ASTER '01 30m resolution)
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Band 5 MIDDLE INFRARED
1 9 8 7
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sq. kilometers
Band 4 NEAR INFRARED
1971
False Color
Composite
Bands 3,4,5
Landsat TM '87
ASTER '01
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2001 ASTER – 30m resolution
2 0 0 1
False Color Composite Bands 1,2,3
Band 1 GREEN
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CROSSTAB module was used to compare both
change and persistence for each of the land cover
classes. The graph above demonstrates amount of
change (in square kilometers) for each from 1987 to
2001. The map below shows both change and
persistence of areas between built and nonbuilt
categories.
Band 2 RED
Band 3 NEAR INFRARED
Prior Knowledge Land Cover Maps
Band 4 MIDDLE INFRARED
False Color
Composite
Bands 1,2,3
Comparison of
Built and
Nonbuilt areas,
1987-2001
1999
1985
Change Analysis of Land Cover
Change from Forest to Residential
After classifying the imagery into appropriate categories, it became evident that change occurred in
different directions for most of the land cover classes. Certain categories, such as residential and
grass, gained while others, like forest and cropland, lost over the period. Increases in residential
and industrial/commercial areas are likely the result of the general growing trend westward of the
Greater Boston area. Expanding golf and other recreational areas increased grass classifications.
Forested and agricultural lands suffered large losses due to these expansions, primarily because
the town is quickly converting from a rural to a suburban setting. Other small changes are likely
due to differences in satellite platforms or slight climate variations, resulting in misclassifications.
1987
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To prepare for change analysis, the following procedures were used
to synchronize and classify the imagery from both time periods.
• Noise was removed from TM bands 2 and 3 using Principal
Components Analysis.
• Both TM and ASTER imagery were geo-referenced to a
Land Cover Classification
matching coordinate system, SPC83MA1.
2001
• Training sites were developed to classify both of the imagery.
• Signatures were created for the 11 different land use categories.
• Maximum Likelihood classifier was used, incorporating prior
knowledge land use maps from MassGIS, to categorize each
pixel into the appropriate land cover classes.
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Training Sites
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NDVI Landsat TM 1987
Expanding residential lands
frequently target forested areas.
Change Analysis using NDVI
Change analysis was also done using the NDVI images from both years. These
images were compiled using the red and near infrared bands from each satellite
imagery. IMAGEDIFF module was used to analyze the direction of change by
creating a standardized anomaly image classified into six categories.
Change greater than one positive standard deviation from the mean shows large
growth in vegetation, while change exceeding one negative standard deviation
show large loss in vegetation. The pixels within one standard deviation from the
mean show small change in vegetation. This is likely due to either differences in
moisture and saturation levels between the 14-year period or in satellite platforms.
Residential replaces forest.
Birchwood community, first built
in late 1980s, shows change
from forest to residential .
NDVI ASTER 2001
Standardized Anomaly
Image
Swapping of Major Land Use Categories
Deciduous to Low Dens. Res.
Deciduous to High Dens. Res.
26.8%
35.2%
5.8%
Orthophoto
Cleared land for new development resembles industrial/commercial.
1m resolution
Total change 14.5 sq. kilometers
4.4%
5.0%
4.6%
3.1%
6.5%
Conifer to Low Dens. Res.
Cropland to Low Dens. Res.
Low to High Dens. Res.
Ind./Comm. to High Dens. Res.
4.4%
4.1%
High to Low Dens. Res.
Low Dens. Res. to Deciduous
Deciduous to Conifer
All other change
Conversion from forest to residential, the dominant land
cover swap, accounted for 35.3 % of the total change.
Within the Birchwood community, positive
standard deviation values are the result of
residential grass replacing cleared land
from 1987. Negative values indicate the
conversion from forest to residential.