Satellite-aided
Field Forestry Applications
Imagery Solutions
Aerial photographs, either
color infrared or black and white, that have been digitized
and rectified are one option.
While they offer high resolution and may be quite recent,
the cost of rectification can be significant. A more affordable
option is a digital orthophoto (DOQ) which has already
been rectified. Although DOQs are usually only available
in black and white, they are widely available and GIS-ready.
However, in Minnesota, most DOQs date back to the early
1990s.
Aerial images acquired by
digital cameras or other multispectral electronic sensors
are a third option.
They are already
in digital format (although they may or may not be rectified),
and the better systems include several spectral bands
in the visible and the near infrared. At this time, the
cost
of this option may be beyond what can be justified for
many forestry applications. A fourth option is digital,
high-resolution satellite imagery which is now approaching
the spatial resolution of digital photographs. It provides
four bands of multispectral imagery in a GIS-compatible
format. Generally, it can be acquired within a short time,
making it a good option when up-to-date information is
needed. However, current costs of about $3,000 for a township
size area may preclude its use. For more information on
high-resolution satellite imagery, see Fact
Sheet 3: Using High-Resolution Satellite Imagery to Monitor
Natural Resources.
When multispectral imagery (with red and near infrared
spectral bands ) from digital cameras or satellite sensing
systems is available, the normalized difference vegetation
index can be a useful image transformation. NDVI is sensitive
to the amount of green vegetation and enhances differences
between vegetation and other cover types.
Sample satellite imagery products
Black & White |
Color |
Color Infrared |
NDVI |
PC |
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Forest
Regeneration Survey >>
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