BRN 9-2 (uncompressed) - Flipbook - Page 51
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17. The San Lorenzo quad (1:62,500) from 1956.
18. The 1:24,000 scale map of San Lorenzo from 1985.
19. The 1:24,000 scale map of San Lorenzo from 1999.
20. The 1:24,000 scale map of San Lorenzo from 2011.
21. The 1:24,000 scale map of San Lorenzo from 2013.
22. The 1:24,000 scale map of San Lorenzo from 2017.
23. The 1:24,000 scale map of San Lorenzo from 2020.
24. The 1:24,000 scale map of San Lorenzo from 2023.
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All of these maps may be downloaded from the USGS
topoview page at this link. All are available in a number of
formats - jpeg, kmz, GeoTiff, and GeoPDF.
ÒWhat is the purpose of this little exercise?Ó you might ask.
It demonstrates two key factors of mapmaking during our
era. One, there has been a shift away from print (hardcopy)
to digital formats. There is extremely little cost associated
with the distribution of these maps. Two, these maps are not
based on new on-the-ground surveys. They are being
produced from existing data Þles, often synthesized from a
variety of sources, many of which are based on digital
surveys produced by aircraft and satellites. This last point is
especially important for natural history research. Since data
can be derived from multiple sources, a wider array of data
can be depicted on a map, and since the base maps are
available in a variety of formats, layering and interpolation is
possible. For example, in the October 2025 issue (Vol. 8,
Number 4) of this journal we discussed the geology of the
Hillsboro Quadrangle. Throughout the issue we utilized the
overlay of a .kmz layer (the Hillsboro geology map) onto a
Google Earth image of the same area. An example from
page 66 of that issue is shown to the right (Ò25Ó). Utilizing
such techniques makes it possible to see the geology (as
depicted on geologic maps) in the Þeld, an overlay of
whatever electronic map source you are using.
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Mapmaking and map usage are not what they used to be, so
what are some examples of what they are?
But before we jump ahead, let us address the changes in the
way the San Lorenzo area was depicted between 1956 and
2023. (Ignoring the changes in cultural infrastructure, new
roads, new housing developments [Casas Adobes, etc.], and
the change in map scale which allow the naming of more
cultural items.) First of all, and somewhat amazingly, the
contour interval is the same in both maps (despite the
difference in scale), 40 feet. The deÞnition of elevation
interval was maintained.
In 1956 the Mimbres river was shown as a perennial river. In
2023 it is shown as intermittent in places and as a ÒwashÓ in
others. In places the ßow of the river (blue line) is actually
the acequia (see T17S R11W Sections 13 and 14).
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