3/14/06

Correlation of selected FGDC Homeland Security Working Group and FGDC
Geologic Data Subcommittee map symbols

The Geologic Data Subcommittee (GDS) has proposed a set of standard map
symbols for geologic and related themes. During the Standards Working
Group review of the GDS standard, it was noted that some GDS symbols
address the same topic or feature as symbols approved by the Homeland
Security Working Group (HSWG). The GDS was requested to identify those
symbols and to provide explanation regarding similarities and
differences with the HSWG standard. This note constitutes the GDS
response.

Upon examination of the HSWG and GDS symbolsets, one general observation
became clear. Because the GDS symbols focus on geologic features, there
commonly are several detailed GDS symbols per HSWG symbol, probably
reflecting differences in focus of data collection and (or) scale of
mapping. The purposes of the HSWG and GDS symbolsets are somewhat
different, but the correlation of symbols from one to the other serves
the useful purpose of facilitating the exchange of information from the
geologist to the Homeland Security community.

1\. Correlation of HSWG Natural Events symbols (see
<http://www.fgdc.gov/HSWG/ref_pages/Natural_Events_ref.htm>) with GDS
symbols:

A.  HSWG symbol for Earthquake epicenter (#6) correlates to the seven
    GDS symbols for earthquake epicenter (see Appendix A, Section 21,
    specifically, symbols 21.1 through 21.7). The GDS symbols are for
    earthquakes of various magnitudes, whereas the HSWG provides a
    single, generalized symbol of similar appearance.

B.  After Shock (#4) does not directly correlate with a GDS symbol,
    because GDS does not use a separate symbol for an After Shock, as it
    is essentially an earthquake -- because most scientific observations
    made by geologists are addressing past events, the distinction
    between earthquake and aftershock usually cannot be portrayed on a
    geologic map; however, maps of recent earthquakes might denote the
    timing of earthquake events with some notation.

C.  Volcanic Eruption (#9) and Volcanic Threat (#10) have some
    correlation with GDS symbols found in Section 18 (Volcanic
    Features). Most of the GDS volcanic symbols address volcanic
    features that can be mapped -- in essence, the standard focuses on
    the deposits and the results of volcanic activity, whereas the HSWG
    symbols focus on current or predicted volcanism. The closest
    correlation to the HSWG Volcanic Eruption symbol is the GDS's
    "Active volcano on small-scale maps" (symbol 18.66); for HSWG
    Volcanic Threat, see also symbols 18.65 ("Recent volcano on
    small-scale maps") and 18.67 ("Inactive volcano on small-scale
    maps"). These GDS symbols are intended for use on small-scale maps
    (i.e., 1:250,000-scale and less detailed).

D.  Landslide (#7) has some correlation with GDS symbols found in
    Section 17 (Landslide and Mass Wasting Features). Most of the GDS
    landslide symbols address features that can be mapped -- in essence,
    the standard focuses on the deposits and the results of landslide
    activity. It appears that HWSG symbols are meant to show locations
    of landslides as point features. The GDS symbols are meant to show
    landslide features at a larger scale, as line and polygon features;
    at smaller scales, areas of landslide deposits are polygons outlined
    by contacts. If the HSWG symbols are meant to represent the
    landslide deposits, then the closest correlation is with symbols
    17.11 (Landslide deposits), 17.56 (Active, reactivated, or
    historically active debris flow...), 17.57 (Dormant-young debris
    flow ...), 17.58 (Active, reactivated, or historically active
    landslide...), 17.59 (Dormant-young landslide...), and 17.65
    (Debris-slide slope...).

E.  Avalanche (#5) may correlate with a GDS symbol; however, because
    this term refers to an event that involves (and likely was caused
    by) snow and ice, geologists rarely can specify with confidence that
    a deposit (especially pre-modern) was the result of an avalanche.
    More commonly, the earth-material deposits that resulted from an
    avalanche are described by geologists according to their physical
    characteristics. Based on those criteria, the HSWG Avalance symbol
    could be correlated with those specified for Landslide, especially
    the debris-flow symbols; however, this isn't recommended.

F.  Subsidence (#8) correlates with GDS symbols in Section 23
    (Miscellaneous Uplift and Collapse Features), specifically 23.9
    (Collapse structure or sinkhole, too small to draw to scale), 23.10
    (Collapse structure or sinkhole, drawn to scale), and 23.11 (Crater
    outline, unspecified origin).

2\. Correlation of HSWG Infrastructure symbols (see
<http://www.fgdc.gov/HSWG/ref_pages/Infrastructures_ref.htm>) with GDS
symbols:

A.  Commercial infrastructure -- Landfill (#25) and Superfund site NPL
    (#27) may correlate with GDS symbols in Section 20 (Hazardous Waste
    Sites), although the correlation is not entirely clear.

B.  Energy Facilities -- symbols #32 through 37 may have some
    correlation with GDS symbols in Section 19 (Natural Resources) and
    symbols 30.3.1 through 30.3.15 in Section 30 (Topographic and
    Hydrographic Features). The HSWG symbols focus on large
    infrastructure such as energy generation and distribution plants,
    whereas the GDS symbols focus on the energy resources and individual
    well and mine locations. If the HSWG has not already considered
    this, the GDS suggests that portraying the locations of subsurface
    mine locations, and oil&gas fields and wells, might prove
    worthwhile, in consideration of their security implications.

C.  Transportation -- symbols #57-73 may have some correlation with GDS
    symbols in Section 28 (Transportation Features) and 30 (Topographic
    and Hydrographic Features). The GDS symbols are the traditional
    symbols long used on topographic base maps. They are quite detailed,
    and are provided to in order to assist geologists in preparation of
    digital base maps upon which geologic maps are portrayed. The only
    specific HSWG symbol found in the GDS standard is Lock (#64), which
    correlates to three GDS symbols for "Canal Lock", found as 30.2.9,
    30.2.10, and 30.2.11.

D.  Water Supply --

    1.  Ground Well (#76) correlates with GDS symbols in Section 26.1
        (Geohydrologic Feature; Water Wells). The GDS symbols are quite
        detailed, and show many types of water wells. If we assume that
        the HSWG is most interested in portraying operating (not dry or
        abandoned) wells for towns, homes, and industry, then
        correlation can be found with symbols 26.1.1; 26.1.6-12;
        26.1.15; 26.1.34-39; 26.1.43-48; and 26.1.51.

    2.  Reservoir (#80) correlates with GDS symbols in Section 30
        (Topographic and Hydrographic Features), specifically symbols
        30.2.36 (Reservoir with natural shoreline), 30.2.37 (Dammed
        reservoir), 30.2.39 (Reservoir, uncovered, with man-made
        shoreline), and 30.2.40 (Covered water storage reservoir).

    3.  The GDS standard includes symbols for water aqueducts and
        pipelines. Paralleling the suggestion made in item 2.B (above),
        the GDS suggests that portraying the locations of these features
        might prove worthwhile, in consideration of their security
        implications.