BRN 9-2 (uncompressed) - Flipbook - Page 53
Assessing Changes Over Time
Earlier we showed the apparent differences in forestation in
T17S R11W from 1956 to 2023 (maps Ò26Ó and Ò27Ó). The
two map details shown may represent actual changes, but
that does not comport with our understanding of the way
these changes manifest. Instead, we believe this is a
mapping artifact of the 1956 map.
Using Google Earth we looked at these areas from 1985 to
2023. We did not see major changes in vegetation in this
area using those images. This is juniper-pi–on habitat and
except for intrusions associated with human habitation it
remains basically unchanged (land usage - for example,
excessive grazing - does not show at this level of detail).
We believe that there are landscape changes which can be
assessed using technologies like Google Earth, even if the
Stitzel Creek assessment did not show dramatic change. To
test this supposition we checked the area north of Kingston
which we used in our comparison of apps and the discussion
of their research potential.
From 1985 to 1996 the Google Earth imagery used Landsat
data and the resolution is not what we generally expect
today from satellite images (see Ò30Ó from January 1985).
In 1996, Copernicus Data was added to the mix and
resolution increased dramatically (see Ò31Ó from September
1996). Copernicus is a European Union system and data set
and its utility as a research source may be more stable, in the
foreseeable future, than data sets and data analysis created
and maintained by the United States.
30
By July 2005, imagery was quite detailed (see Ò32Ó). This
data is from NMRGIS.
Changes associated with the Silver Fire were dramatic, as
shown in the image from November 2014 (Ò33Ó). An image
from January 2023 (Ò34Ó) shows some vegetative recovery
over the intervening 8.5 years.
This type of tool can be useful in accessing changes over
time but is limited by the short period over which data are
available. Images from the last thirty years have enough
resolution to be useful at large scale, but visual granularity is
limited.
Google has introduced a new tool which provides a more
robust time lapse assessment of change. Watch a sample of
this tool from the area discussed above at this link. Part of
the data used in this new tool is the same as that discussed
above, so you can see the changes in visual resolution occur
quite dramatically.
31
The Copernicus browser provides access to various visual
Þlters and augmented data sets to enhance the usefulness of
the visual images. Take for example, the application of
Þlters which allow the assessment of moisture (see Ò35Ó as
an example of the application of the moisture index). The
scene assessment (Ò36Ó) also tracks the moisture index. In
the scene assessment, green equates to vegetative cover
and yellow equates with rock and bare earth. The short
wave interval composite imagery (Ò37Ó), which is one tool
used to assess amount and type of vegetative cover, tracks
the moisture assessments as do other vegetative cover
assessment tools.
These tools and others discussed previously in this journal
allow large scale assessment of vegetative cover, temperature variation, moisture, and other data sets at greatly
reduced cost and signiÞcantly enhanced efÞciency and
effectiveness. Such tools are a good investment.
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