Examination of the first hundred ship histories using the Journey Plotter shows that almost every ship has navigation errors.
These errors range from relatively minor (a few obvious glitches) to quite major (a lot of missing navigation).
While the navigation for every ship will be checked before it goes online, this process (which has taken several people a combined total of a month or more to fix for the edited logs) will go more quickly if ship editors can do some of the basic checking and fixing before submitting their ships.
This navigation checking can be done before, during, or after the history-writing, depending on each editor's preference.
When you send in your completed files, it would be useful to us if you could write a sentence or two (no more) about the amount of checking that you did.
(We understand if you feel this checking is too much of an added burden. We will do it for you, if so.)
Note that Journey Plotter currently only works on Windows, therefore users of other operating systems are excused these duties!
If you think you have found a problem, but you are not sure or you don't know how it can be fixed, please add a line in your file at the appropriate place that says 'Navigation problem'. This will allow us to find these unresolved problems quickly and see if they can be fixed.
The following list summarises the problems that we have found so far.
The most obvious errors are sudden spikes; these can vary from jumps of ~100 miles to global in size. They can be due to:
These can be caused by:
These are a little more subtle and are usually seen as a 'large' jump between positions on consecutive days, with a small change on the days before or after. They are fairly obvious when a ship is steering a straight course, but will probably not be seen when there are many course changes.
What is 'large'? Basically, 'large' is anything that looks seriously different to the adjacent days' positions. Check the positions against the log scans and change them if necessary.
These can be due to errors in the original log, errors in transcribing, or strange positions produced by the Old Weather location extraction program. Note that the extraction program's positions are rarely exactly the same as the positions in the logs. Please fix these if you can easily identify the error.
Some log keepers wrote their positions with the degrees and minutes separated by what looks like a decimal point. Some Old Weather transcribers have then mistakenly entered these as decimal degrees. For example, a ship latitude of 35° 09' might appear in the log as 35.9. This could then be wrongly transcribed as Lat 35.9, instead of the correct Lat 35.2.
These are often not obvious. A potential give-away is when you see a group of latitudes/longitudes given to two decimal places instead of the usual one. While these errors are usually not very significant in the open sea, they can often produce positions that plot onshore in more restricted waters, such as the Red Sea.
The extraction program will sometimes give us latitudes/longitudes in which the decimal places are set to 0 (zero) regardless of the value. Thus, 12.9, 12.1 and 12.0 all appear as 12.0. These often occur in batches of consecutive positions. In a Journey Plotter map, they can produce a 'boxy' appearance which can help their identification. Please correct these to their log scan values when you come across them.
In many cases, a position has not been provided in port before or after a ship has been at sea. Journey Plotter will then show a ship route starting or ending at sea and disconnected from land. Please add these port locations if you can.
Journey Plotter produces four reports which are worth looking at.
The first report (
If a log-page contains multiple days on one page, please insert a copy of the link to the log-page and add the date for each day.
The second report () lists those dates which have more than one entry in the file. Possible reasons for duplicate dates are: an incorrect date has been entered in the original log; a date has been incorrectly transcribed; or there are genuine multiple entries. Please fix these where you can identify the error.
The third report () lists both the dates for which no position has been transcribed and the dates for which a lat/long is present but which has been incorrectly formatted (please fix these).
The fourth report () lists dates where the distance from the recorded position of the previous day is greater than the maximum average speed of the ship would allow. Check the position for this date, or the day before this date, as most probably one of these two positions is incorrect, and fix the position if possible.