The Project Database

The Project Database

 

After that initial processing of CLIWOC, TSTD, HURDAT, and my database of Catalan voyages, I developed the project database as an Excel 2010 workbook named ACLS_Voyages_Data.xlsx. It contains 73 voyages by 41 vessels between 1752 and 1900 sailing between Europe, Africa, the Caribbean, South America, North America, and Asia carrying cargos of coffee, sugar, spices, gold, and many other products as well as enslaved Africans. The daily position and cargo data for 15 of the vessels making 17 of the voyages came from my database of Catalan voyages while that for the other 26 vessels and 56 voyages came from CLIWOC. Of the 41 vessels, 27 made a single voyage; 4 made 2 voyages; 4 made 3 voyages, 4 made 4 voyages, and 2 made five voyages. Vessels making multiple voyages were designated by different letters for each voyage: for example, Middelburgs_Welvaren_A versus Middelburgs_Welvaren_B.

The following table shows the breakdown by nationality.

Nationality	Number of Vessels	Number of Voyages	Slaving Voyages	Slaving Voyages Also in TSTD
British	4	4	2	2
Dutch	22	52	46	42
Spanish	15	17	0	0
TOTAL	41	73	48	44

Four of the Dutch slaving voyages do not appear in TSTD because they did not carry slaves across the Atlantic. The Zephyr was a naval brig that sailed from the Netherlands directly to Suriname; while on the Berbice River in Guyana in February 1764, the Zephyr took aboard 72 slaves from the Sieben Provinzen, a vessel name that does appear in TSTD but not for any voyages during the 1760s. Two of the three voyages of the Mercurius do not appear in TSTD because after taking aboard some slaves in Africa, the captain traded them and returned directly to the Netherlands with cargoes of ivory and gold. Similarly, one of the two voyages of the Granadier initially took aboard enslaved Africans but returned directly to the Netherlands with a cargo of ivory, wood, and wax.

Two of the British and two of the Spanish voyages did not carry cargoes at all because they were voyages of scientific exploration. I chose to include them because of their potential interest. The British ones were James Cook’s first two voyages: in the Endeavor, 1768-1771, and the Resolution, 1772-1775. The Spanish ones concerned the Alessandro Malaspina expedition of 1789-1794, involving two ships named the Descubierta and the Atrevida.

Another of the Spanish voyages was by the Astuto from Peru to Spain in 1778 with a cargo of coinage, jewels, gold, silver, copper, tin, cacao, cacao hulls, chocolate, and sugar. During the voyage, ten people kept separate logbooks and thereby generated ten separate records of their position that I chose to include because of the potential to evaluate the relative precision of their estimates.

Before importing the database into the GIS, I used Excel’s standard tools such as fill, find and replace, and sort to modify it in various ways because of the much higher productivity possible with Excel than trying to make the modifications once in ArcGIS. I standardized spellings of vessel names, captain’s names, place names, and so on, typically to conform modern usage. I added underscores to join words, for example, changing Drie Gezusters to Drie_Gezusters to avoid problems with ArcMap recognizing field names. Because CLIWOC had data on the number of crew members, tonnage, armaments, and other interesting information but presented it in a single field called OtherRemarks, I added separate fields for CrewSize, Tonnage, Armaments, and so on. And I added a field named DayOfWeek and populated it using the fill series tool and the calendar calculator at http://www.timeanddate.com.

Once all of those the changes had been made, most productively done in a single worksheet, I saved each voyage as a separate worksheet within the workbook because the free version of ArcGIS Online will only accept files of limited size, up to a maximum of 1,000 features. Since each voyage included several hundred features, each one representing a daily position on a particular date with associated attributes such as cargo, I would not be able to add them to ArcGIS Online using the free, non-subscription version as a single file.

A remaining issue involved the lack of vessel positions for some vessels while they were in port. I used the Geodata table in CLIWOC21.mdb to create another worksheet called Ports_and_Landmarks to locate the sometimes obscure places noted in the logbooks. The Geodata table provided an initial list of places and their latitudes and longitudes for that worksheet. I then added more places to it, especially regarding the Catalan voyages and the places along the coasts of West Africa and the Gulf of Guinea. David Eltis and David Richardson, An Atlas of the Transatlantic Slave Trade (New Haven: Yale University Press, 2010) proved helpful in locating obscure place references along the African coast. I used GoogleEarth to determine their latitudes and longitudes in +/- decimal degrees and copied/pasted them into the Ports_and_Landmarks worksheet. That worksheet then allowed me to populate the empty latitude and longitude cells for vessels in specific ports with the latitudes, longitudes for those ports.

A final remaining issue to ready the database before importing it into ArcGIS concerned missing days, latitudes, and longitudes. These occurred in three types of instance.

The first type of instance concerned entirely missing segments of the voyage. For example, many of the slaving voyages made their first African landfall along the coast of West Africa between present-day Senegal and Liberia, followed the coast southward and eastward while trading for enslaved Africans, and then departed for the Americas from a port in the Gulf of Guinea, such as Elmina in present-day Ghana. The logbooks generally did not record latitude and longitude positions while following the coast because sailors navigate by coastal landmarks when they can. Often there are no entries at all; sometimes a general description of the itinerary is given as a single entry that encompasses weeks or months of coastal sailing and trading; and in a few logbooks, landmarks and anchorages are noted for particular dates. For entirely missing segments, I simply ended with the last record of the previous segment, such as from Fort Rammekens, Netherlands to Cape Mount on the Liberian coast, and resumed with the first record of the next segment, such as from Elmina, Ghana to Paramaribo, Suriname. For segments that gave landmarks on particular days and places that the vessel anchored for, sometimes, weeks at a time, I added those days and used the latitudes and longitudes of those landmarks, anchorages, and ports in my Ports_and_Landmarks worksheet to add the missing positions for that segment.

The second instance concerned single days that were clearly missing from particular voyage segments. For example, if a day was missing in mid Atlantic from a segment of a voyage from the Gulf of Guinea to Suriname, I simply added that day and used the last known latitude and longitude as the position. In cases that the day was present but either the latitude, longitude, or both were missing, I again used the last known latitude, longitude, or both. Once the voyages were mapping in the GIS, I knew it would be possible to use the interactive editing tool to select those position markers and drag them into what amounted to a best estimate, interpolation of the missing position. In other words, the missing day, latitude and longitude would be dragged to a position intermediate to the position of the day before and the day after.

The third instance concerned days and positions, often multiple, at the ends of segments. A common instance of this occurred when vessels approached Europe on the homeward segment of a voyage. Sometimes the last entry in the logbook recorded sighting The Lizard, a lighthouse on Lizard Point that marked the Atlantic end of the English Channel. In other logbooks, The Lizard also marked the last latitude, longitude entry but other types of entries followed. Sometimes a single entry gave the date of arrival in a port, such as Fort Rammekens. Other logbooks included multiple entries that gave sightings of key landmarks as the vessel progressed up the Channel, such as Portland, the Isle of Wight, and Dover. For the first type, I ended the segment at that point, for example, at the Atlantic end of the English Channel. For the second type, I added the days between the end of the latitude, longitude entries to arrival in a specific port on a particular day and used the latitudes, longitudes of that port, of landmarks given, and of either the last known or next known position. Again, once the voyages were mapping in the GIS, I knew it would be possible to use the interactive editing tool to select those position markers and drag them into what amounted to a best estimate, interpolation of the missing position.

(The next post will deal with importing the database into the GIS.)