Remote Sensing in the CPC Ecuador Projects
Remote sensing is the backbone of the spatial analysis in this
project. We currently have a 30-year time series of Landsat imagery
for this region, spanning 1973-2002. We have also recently begun
acquiring a collection of high-resolution IKONOS imagery for select
locations in the study area. The Landsat MSS (Multispectral Scanner)
and TM (Thematic Mapper) imagery provide us with a wide view of
the entire region, allowing us to track broad changes in LULC, while
at the same time providing us with a fairly detailed view of changes
internal to our study fincas. The 79m resolution of Landsat MSS
and 30m resolution of Landsat TM imagery makes it possible to detect
areas as small as 0.6 ha and 0.1 ha, respectively, although we tend
to focus on a minimum mapping unit of 0.5 ha. Since late 1999, the
acquisition of Landsat 7 ETM (Enhanced Thematic Mapper) with the
addition of a 15m panchromatic band to the standard compliment of
multispectral bands allows even more detail to be garnered from
these region-wide images.
A Landsat TM image of a small town in the Oriente
(click for larger image)
By comparison, the IKONOS imagery (4m multispectral, 1m panchromatic)
allows for extremely detailed viewing and analysis, albeit over
much smaller regions. A typical IKONOS image covers roughly 120
km2, while a typical Landsat TM image covers 34225 km2. However,
the improvement in spatial resolution more than makes up for the
significant decrease in areal coverage.
By comparison, here is an IKONOS
multispectral image of the
same town…
(click for larger image)
… and an IKONOS panchromatic image of the
central part of the town. (click for larger image)
The primary purpose of the Landsat time series is to track changes
in land use and land cover (LULC) over time. Through the use of
a supervised classification methodology, the LULC for each of these
time periods can be generated. The classes of interest vary between
the NASA projects in the colonist area and the NIH project in the
indigenous area. More detail on the LULC classification methodology
will be posted in the near future.
After the LULC classifications have been generated for each date
of interest, the LULC history can be tracked for each sampled finca
madre in the colonist study area, or for the chacras used by each
indigenous household. These LULC histories are combined with the
socio-economic and demographic (SED) data in multivariate analyses
that are designed to evaluate the SED determinants of LULC change.
Another useful product that has been generated is the change detection.
Several approaches have been used to look at how the LULC has changed
over time. The most common method is the post-classification change
detection, in which the LULC assigned to each pixel is tracked through
time. However, there are a variety of pre-classification change
detection methods that have also been performed. More information
on change detection and other methods will be posted in the near
future.
