-4- 
The measuring unit used contains one PtlOO and is mounted at the inside of the ship’s 
hull in the engine room about 2 m above the ship’s bottom and good in front of the 
engine’s radiator water outflow, thus working as a contact thermometer. The thermo 
meter is insulated by thick layers of foam material against the warm engine room 
temperature. The values measured are telemetered by a two conductor cable to the 
navigation bridge where they are displayed continuously. These thermometers have 
proved to be reliable for years on several vessels used within the framework of the DHI 
SST programme (TRACKOB). As a matter of fact, instead of the real SST the tempera 
ture in about 6 to 7 m depth is measured - depending upon the ship’s draught. For prac 
tical comparisons, however, this is an advantage due to the unreliable initial data cycles 
of each profile caused by the large time constant of the XBT thermistor. On the other 
hand, for the vast majority of profiles a homothermic top layer prevails. 
Fig. 2 presents a scatter diagram of PtlOO SST versus XBT temperatures at the same 
depth. The linear fit calculated from 240 values produced from July through December 
shows an almost constant mean temperature difference T(SST) - T(XBT) of about 
+ 0.15 K for the whole scale. Taking into account various error sources as the LED 
display resolution of 0.1 K, the PtlOO accuracy of +_ 0.1 K, a temporal error of about 
_+ 0.1 K (assumed synchronization error between PtlOO reading and XBT reading), and 
the XBT temperature accuracy as given by Sippican, Inc. as ± 0.2 K, the result of Fig. 
2 verifies the reliability of the contact thermometer used. 
SST ► 
Fig. 2: 
SST as measured by "Mini Medes" versus XBT temperature readings at the same 
depth (6 to 7 m)