ICOADS Web information page (Tuesday, 08-Nov-2005 23:58:46 UTC):

Translation of the US Maury Collection: Temperature Corrections

Figures 1-2 are plots from the keyed data, limited to reports with originally
reported latitude/longitude (a fraction of the complete data).  Only two reels,
56-57, contained (some) temperatures labeled during digitization as Celsius;
Fig. 1 aggregates all these data together into one plot.  Data from the
remaining reels were all labeled Fahrenheit; Fig. 2 aggregates all these
data, including any data from reels 56-57 labeled as Fahrenheit, into one

Figure 1: All temperatures labeled Celsius (reports with lat/lon).
Figure 2: All temperatures labeled Fahrenheit (reports with lat/lon).

All reels were plotted individually, to isolate reels contributing to the
erroneous displacements of temperatures (i.e., groupings outside the
normal for a given latitude) evident in Figure 2.  The problems we
isolated arose from two factors: (a) Temperatures mislabeled during keying
(labeled as Fahrenheit, but should be Celsius).  Sometimes there were
mixed units among the three thermometers (for air and sea surface
temperatures, and the thermometer attached to the barometer) that were not
all properly labeled.  (b) In some cases the digitized temperature data
were improperly shifted to the right or left within the allocated field,
thus shifting the numeric data by an order of magnitude.  Details about
the corrections applied to individual voyages are available in the
conversion specifications.

It is not known whether any of the temperatures in the US Maury Collection were
reported in Reaumur.  Few if any metadata explicitly stating the temperature
units were available on the original logforms, and during digitization the
Chinese made an educated guess about the units of the data in each report.
If Reaumur data exist, they probably reside among the voyages that either
were originally labeled, or reinterpreted during correction processing,
as Celsius (i.e., selected voyages from reels 15, 27, 46, 56-57, 67, 69, 74,
77, and 84).  Further research would be required to try to identify Reaumur
data, if they exist, focusing on voyages in the tropics where temperatures
measured in the Celsius and Reaumur scales could be more easily separated.

Figures 3-10 are before/after plots for individual reels that showed clear
problems.  The "before" plots are limited to data with originally reported
latitude/longitude; the "after" plots also incorporate data with interpolated
locations.  In the "before" plots, data labeled Fahrenheit are converted to
Celsius; the "after" plots show data as converted into Celsius in LMR format.
Corrections were also made to some attached thermometer readings (not shown;
corrected readings were used to adjust pressure, but not preserved in LMR).

Figure 3: Reel 15 (a) before correction (b) after correction (LMR).
Figure 4: Reel 46 (a) before correction (b) after correction (LMR).
Figure 5: Reel 56 (a) before correction (b) after correction (LMR).
Figure 6: Reel 57 (a) before correction (b) after correction (LMR).
Figure 7: Reel 69 (a) before correction (b) after correction (LMR).
Figure 8: Reel 74 (a) before correction (b) after correction (LMR).
Figure 9: Reel 75 (a) before correction (b) after correction (LMR).
Figure 10: Reel 84 (a) before correction (b) after correction (LMR).
Figure 11: All air temperatures after correction (LMR).
Figure 12: All sea surface temperatures after correction (LMR).


[Translation information][US Maury Collection]

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Updated: Nov 8, 2005 23:58:46 UTC