-------- Original Message --------
Subject: RE: more on the extent of sea floor mapping
Date: Tue, 1 May 2012 11:36:56 +0200
From: Jan Smits <[log in to unmask]>
To: Maps, Air Photo, GIS Forum - Map Librarianship <[log in to unmask]>
Julien Thoulet drafted bathymetric maps for the territory of France
(Densités de sondages et véracité des cartes bathymétriques
sous-marines. In: Annales de l'Institut Océanographique. Paris, 1911.).
In these four maps he draws hypothetical isobaths, which are based on
respectively 15, 31, 154, and 308 altitude measurements per 153,821
square miles for France and the adjacent territories. These give
schematic negative relief maps, which hardly even approximate the true
relief of the territory. Thoulet wanted to show that the few bathymetric
measurements available for the vast oceans would only vaguely
approximate the true relief of the ocean floors.
In Petermann's Geographische Mitteilungen 59. Jahrgang, 1913, the
following map appeared:
Tafel 40 : Bathymetrischen Karten von Frankreich zur Veranschaulichung
der Richtigkeit bathymetrischer Karten überhaupt / von Julien Thoulet. -
Scale [ca. 1:5.835.000] (W 5°-E 10°/N 52°-N 42°). - 4 maps : colored ;
all 18x23 cm, on leave 47x52 cm.
Original title: Densités de sondages et véracité des cartes
bathymétriques sous-marines (Annales de l'Institut Océanographique,
Paris, 1911).
Extrapolatie is doorberekend naar aangrenzende landen.
Op de kaart van Frankrijk zijn hypothetische isobathen getekend, die
geextrapoleerd zijn vanuit een beperkt aantal hoogtepeilingen (15, 31,
154, 308 per 153.821 vierkante mijlen), waardoor een schematische
negatieve hoogtekaart ontstaat die maar beperkt de werkelijkheid
benaderd; de reden voor deze weergave is om aan te geven in hoeverre
bathymetrische kaarten het zeebodemreliëf accuraat weergeven.
Is part of: Die Lotungsdichtekarte von J. Thoulet / von Max Groll. P.
250-251.
Class.: <4.280>; 256 : diepteweergave
From: Petermann's maps : carto-bibliography of the maps in Petermanns
geographische Mitteilungen 1855-1945. 't Goy-Houten, Hes & De Graaf
Publishers. 584 p. : ill., krt. ; 33 cm + cd-rom.
In the series: Utrechtse historisch-kartografische studies, ISSN 1568-2072.
In conclusion: those parts of the ocean floors, that have not been
densely surveyed, mostly have been interpolated from adjacent parts of
the ocean floors.
With kind regards,
Jan Smits
Koninklijke Bibliotheek, National Library of The Netherlands
-----Oorspronkelijk bericht-----
Van: Maps, Air Photo, GIS Forum - Map Librarianship
[mailto:[log in to unmask]] Namens Angie Cope, American
Geographical Society Library, UW Milwaukee
Verzonden: maandag 30 april 2012 18:25
Aan: [log in to unmask]
Onderwerp: more on the extent of sea floor mapping
-------- Original Message --------
Subject: more on the extent of sea floor mapping
Date: Mon, 30 Apr 2012 12:19:48 -0400
From: Fry, Michael <[log in to unmask]>
To: Maps, Air Photo, GIS Forum - Map Librarianship
<[log in to unmask]>
Last week I tried to provoke some conversation about this quote: "/We
have more detailed maps of the surfaces of Mars and Venus than we do of
parts of our own ocean floors/." I've found number of similar claims
[below], some of which provide some background and context for the
claims they make.
Although most of these quotes are from very reputable sources, I'm still
a bit bothered by what some of them imply, namely: we don't have maps of
the whole sea floor, and we can only call something a "map" if we've
been there and surveyed it (or, perhaps, if it surpasses some heretofore
unidentified threshold of accuracy).
I understand that much of seafloor has not been surveyed with the latest
echo sounding technology (and maybe hasn't been surveyed with so much as
a rope and some lead weights). But does it really follow that our "maps"
of Mars and Venus--neither of which we've set foot on--are more accurate
than my GEBCO charts? Are my GEBCO charts fiction? Are our topo maps,
many of which I understand have DEM-based elevation data, not legitimate
maps? Is Bob Ballard, for example, being dramatic when he says that a
Heezen & Tharp map of the ocean floor shouldn't be called a "map"? What
does that say about our collections? Is there a double standard for what
can legitimately be called a "map"?
I'm not trying to be controversial--just trying to separate rhetoric
from reality and better understand how we assess the accuracy of
geospatial info. (And full disclosure: Bob Ballard is an
Explorer-in-Residence at National Geographic, where I work.)
Thoughts??
mf
==========================
Amitai Etzioni
<http://www.cnn.com/2012/04/09/opinion/etzioni-space-oceans/index.html>
[via CNN]
"/Ninety percent of the ocean floor has not even been charted/"
Bob Ballard
<http://www.wbur.org/npr/106246285/robert-ballard-50-years-exploring-deep-waters>
[via NPR]
/"We have better maps of Mars than our own planet."/
GEBCO <http://www.gebco.net/about_us/news_and_events/atlantis_found.html>
/"It is true that we have better topographic maps of Mars, Venus and
Earth's Moon than we do of Earth's ocean floor. The Mars maps are 250
times more accurate, for example. The oceans are vast and actual
measurements of their depths are few, especially in the deep ocean basins./"
Bob Ballard
<http://www.ted.com/talks/robert_ballard_on_exploring_the_oceans.html>
[via TED conference presentation in which he advocates for more
exploration of the oceans]
At 2:35 he points to what looks like Heezen & Tharp's /The Floor of the
Oceans/ "map" and says "/This is a characterization of what [earth]
would look like if you could remove the water. It gives you the false
impression that it's a map. It is _not_ a map./"
At 14:48 he says "/We have maps of Venus but not of the western
territorial trusts/ [i.e., Mariana Islands and other Pacific islands,
atolls, etc.]"
Scripps
<http://www.sio.ucsd.edu/About/Research_Overview/Earthquakes_and_Geology/>
/"Scientists at Scripps and the National Oceanic and Atmospheric
Administration (NOAA) have developed the first digital map of the global
seafloor. Before its release, scientists had better maps of the surface
of Venus and Mars than of Earth's ocean bottom./"
Scripps <http://topex.ucsd.edu/sandwell/publications/111.pdf>/NOAA
<http://topex.ucsd.edu/sandwell/publications/111.pdf>
/Current bathymetric charts are inadequate for many...applications
because only a small fraction of the seafloor has been surveyed. Modern
multibeam echosounders provide the best resolution, but it would take
more than 200 ship-years and billions of dollars to complete the job...
After five decades of surveying by ships carrying echosounders, most of
the ocean floor remains unexplored and there are vast gaps between
survey lines. The primary reason for this lack of data is that ships are
slow and expensive to operate. For example, a systematic mapping of the
deep oceans by ships would take more than 120 years of survey time./
GEBCO
<http://www.nerc.ac.uk/publications/planetearth/2004/summer/sum04-gebco.pdf>
/"There are still large areas of the ocean floor that haven't been fully
surveyed. Data are often concentrated along isolated ship tracks, and
there may be many miles between one track and the next. Scientists may
need other information to help them interpret what lies in between. In
recent years satellite altimetry data has helped. This measures the
height of the sea surface. Small variations in sea height can be related
to changes in the Earth's gravity field. This in turn can be related to
features on the ocean floor. For example, the sea surface may be high
over a seamount, or show a depression, or trough, over a trench. This
can help scientists interpret the size and shape of features on the
ocean floor, although there are some limitations, for example in areas
covered by sediment./"
US Naval Research Lab
<http://mp-www.nrl.navy.mil/marine_physics_branch/introduction.htm>
/"In the last few decades, increasingly detailed (high resolution)
mapping projects have revealed the surfaces of the Moon, Mars//, Venus,
several asteroids, and the larger moons of Jupiter and Saturn to
resolutions of better than 100 meters (about the size of a football
field), and in some cases (for example the Jovian moon Europa, and Mars)
to better than 10 meters (the size of a large automobile). Planetary and
lunar mapping missions have generated numerous //research
publications//.The Earth's oceans//cover an area larger than one Mars
sized planet plus three Moons. Only a small part of the ocean floor has
been mapped to the 100 meter resolution the Magellan radar mapping
mission achieved on Venus, and areas the size of cities have scarcely or
never been crossed by a survey ship./"
NOAA <http://topex.ucsd.edu/sandwell/publications/74.pdf> [via Science
magazine]
/"Conventional sea floor mapping is a tedious process. Ships have
measured depth with single-beam echo sounders since the 1950s, but these
data are sparsely distributed (hundreds of kilometers between surveys)
and may have large errors in navigation and digitization. More accurate
multibeam swath-mapping systems came into use on some ships in the
1980s, but in the deep ocean, these were deployed primarily along
mid-ocean ridges. Some surveys are classified as secret in military
archives or remain proprietary for economic or political reasons. Global
bathymetric mapping requires some means of combining these heterogeneous
soundings and estimating depths in the regions where survey data are
sparse. Traditionally, bathymetric contours have been drawn by hand so
that intuition (or prejudice) fills the gaps in coverage. The contours
may then be digitized and interpolated to produce gridded estimates. The
last global syntheses were made in the late 1970s and early 1980s,
yielding the fifth edition of the General Bathymetric Charts of the
Oceans (GEBCO)."
/
NOAA <http://www.tos.org/oceanography/archive/17-1_smith1.pdf> [via
Oceanography magazine]
/"Many people have seen a map of the ocean basins, and naturally might
assume that such maps are accurate and adequately detailed. People are
usually astonished to learn that we have much better maps of Mars,
Venus, and Earth's moon than we have of Earth's ocean floors...There is
no steady and systematic effort at mapping our home planet's
oceans...Bathymetric survey tracks cover the remote oceans as sparsely
as the Interstate Highway System covers the United States. Imagine, for
a moment, producing a topographic map of the United States using only
data collected along the interstate highways. How would you interpolate
the gaps?"
/
--
Michael Fry
Senior Map Librarian
National Geographic Society
1145 17th St. N.W.
Washington, D.C. 20036
202.857.7098 <tel:202.857.7098>
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