30 January Daily Log

Latitude and Longitude
The days are beginning to run together. You get into a routine here at sea, but every day, there is new data arriving from the Chirp and you have new conversations with people on board.

This morning began with the Chirp deployment. Later, J.P. showed the students on watch, Louisa, Ramsey and Saro, and me around some of the science lab instruments, for example, the meteorological data monitor that tracks air temperature, water salinity, and temperature among many other things. It is fascinating to me that the air temperature, which feels quite hot and muggy, is in fact slightly cooler than the water temperature!

J.P. also gave us a brief introduction to the units of latitude and longitude, degrees, minutes and seconds (used to plot our position) and their relation to nautical miles (nm), and we discussed how and why our local time zone is 10 hours ahead of Greenwich Mean Time (GMT) which is the time at the prime meridian. Since a ship travels through many different time zones, logs are kept, and clocks are set in both GMT time and local time. Also, the difference in time between local noon and GMT noon can be used to calculate longitude (and vice versa). For this reason, the development of an accurate sea-going clock was a critical invention for navigation.

Here´s an example: because it takes 24 hours for the Earth to rotate (1 day) and there are 360 lines of longitude around the Earth, in one hour the Earth rotates approximate 15 degrees of longitude (360 degrees � 24 hours = 15 degrees/hour). Time zones are generally set 15 degrees of longitude apart for this reason. So, to determine how many hours between GMT time and our local time, we would compare the line of longitude we are at with that at GMT. For simplicity´s sake, let´s say we are currently at 150° East longitude. GMT is at the Prime Meridian or 0 degrees longitude. So, our difference in longitude is 150 degrees. Dividing 150 degrees by 15 degrees/hour, we find the difference in time is 10 hours. Therefore, at 150 degrees East longitude, we are 10 hours ahead of GMT which is at 0°.

Following lunch, we had our second lecture. Every day, the students from University of Papua New Guinea are offered an hour-long lecture given by the scientists onboard. I attend the lectures along with Jason, who works at the Geological Survey of Papua New Guinea and is joining us on this leg. The lectures relate to the work that is being done onboard. Yesterday, Chuck Nittrouer began with an overview of the Fly River dispersal system and the Gulf of Papua. He outlined why this it is an interesting study site, and reviewed the basics of four types of oceanography: physical, geological, chemical and biological.

Navigation
Today, John Crockett, a Ph.D. candidate at the University of Washington, taught us about navigation. We reviewed the basics of latitude and longitude, and then reviewed the tools used when charting a course. You need four things: (1) a chart (map) of the area, (2) a divider which allows you to measure distances, (3) parallel rules or triangles to find the compass heading on the rosette to your position on the chart, and (4) a pencil to plot your course. Compasses (also called rosettes) as well as latitude and longitude lines are printed on nautical charts to make charting a course easy. John then had us each take turns find charting the course after he provided the heading (bearing) and the distance in nautical miles (nm). It was an enjoyable exercise, and although we all ended up on land, rather than in the water where we were heading, it wasn´t a bad first attempt!

Weather
(Today's weather and location at 0900)

Air Temperature: 28.7°C
Water Temperature: 30°C
Salinity: 33.02 PSU
Barometric Pressure: 1008.0 cmbar
Precipitation: 14.7mm (last 24 hours)

Location
Longitude: 144° 20´ E
Latitude: 8° 43´ S

Menu
Breakfast: Bacon, ham, eggs, potatoes, fresh fruit
Lunch: Chicken a la king, fish and chips
Dinner: Shrimp Creole, grilled tuna steaks, rice, veggie
Dessert: Chocolate cake