The Position Tools pane assists in calculating the ship's position using sighted geographic points, bearings and distances. If the Position Tools pane isn't displayed, show it by selecting Position Tools in the Tools menu.
Information for a maximum of three points can be entered to calculate the position.
Positions
Positions are entered in the point's Position field, where the latitude and longitude must be separated by a comma.
A wide variety of notations is supported.
Both latitude and longitude can be entered in decimal degrees, or degrees and decimal minutes, or degrees, minutes and decimal seconds. The ° (degrees), ' (minutes) and " (seconds) symbols are optional, but if not used a space separating the individual values is required.
To indicate the hemisphere the value can be preceded by a - or + sign, where the latter is optional, or followed by a compass direction, N or S for the latitude and E or W for the longitude. If no sign or compass direction is given + is assumed.
The terms Lat and L(o)ng are allowed to be part of the position, where the character case of the term is ignored.
Examples of valid entries:
| Entered value | Equivalent in degrees |
|---|---|
| 54.4, 4.5 | 54.4, 4.5 |
| 31 52 30 N, 125 48 00 E | 31.875, 125.800 |
| 17°9'30"S, -77° 19' 30" | -17.15833, -77.32500 |
| 36°57', 76.36W | 36.95, -76.36 |
| 40 14 N, 73 47.5W | 40.23333, -73.79167 |
| Lat 61.60, Long -169.90 | 61.60, -169.90 |
A white exclamation mark in a red circle at the far end of the field is shown when the entered position isn't recognised.
When the Enter key is pressed, or if the position field loses focus, and a valid position has been entered, a marker bearing the name and in the colour of the point will be shown on the map.
Instead of entering a position for a point, it can be selected from the map. Click the button for the appropriate point and click the map at the location where the point should be.
To cancel picking a point, click the button again, or press the Escape key.
A point's marker on the map can be dragged to a different position.
Click the marker and, whilst keeping the mouse button pressed, drag the marker to its new location.
The map will pan automatically when approaching the edge.
When the mouse button is released the updated position will appear in the Position field.
Bearings
Bearings to a point are entered in the point's Bearing field, either in degrees, as a bearing angle, or as a compass point.
A bearing in degrees can be entered in decimal degrees, or degrees and decimal minutes, or degrees, minutes and decimal seconds. The ° (degrees), ' (minutes) and " (seconds) symbols are optional, but if not used a space separating the individual values is required.
Examples of valid entries:
| Entered value | Equivalent in degrees |
|---|---|
| 293° | 293 |
| 330.7 | 330.7 |
| 57°45'18.5" | 57.75514 |
| 264° 28' | 264.46667 |
| 187 51 09.8 | 187.85272 |
Bearing angles are case insensitive, and the angle can be entered in decimal degrees, or degrees and decimal minutes. The ° (degrees) and ' (minutes) symbols are optional, but if not used a space separating the individual values is required.
Examples of valid entries:
| Entered value | Equivalent in degrees |
|---|---|
| N35°W | 325 |
| S18°45'E | 161.25 |
| s84.5w | 264.5 |
| N45e | 45 |
| N18 30W | 341.5 |
Compass points can be entered using the 256-wind, or 256-point rose, can be clockwise or anticlockwise, and are case insensitive.
The by in a compass point can be abbreviated to b or x.
The 256-wind rose allows for the fractions ⅛, ¼, ⅜, ½, ⅝, ¾ and ⅞, which can also be entered as 1/8, 1/4, 3/8, 1/2, 5/8, 3/4, and 7/8.
Examples of valid entries:
| Entered value | Equivalent in degrees |
|---|---|
| N | 0 |
| E by S | 101.25 |
| SxW | 191.25 |
| WbyS5/8W | 265.78125 |
| SbE¼E | 165.9375 |
| wnw | 292.5 |
| NE by E3/8E | 60.46875 |
Each bearing can be true or magnetic, and also relative to the ship's heading.
Setting the True check box assumes the given bearing is using true north, otherwise magnetic north is assumed.
Setting the Relative check box makes the given bearing relative to the ship's heading, otherwise the bearing is absolute, i.e. from the magnetic or true north.
A white exclamation mark in a red circle at the far end of the field is shown when the entered bearing isn't recognised.
If the point's marker is shown on the map, a line showing the bearing will be drawn on the map for a valid bearing.
The bearing line is drawn as a great circleopen_in_new, so it might not appear as a straight line on the map.
Distances
The optional distances to a point are entered in the point's Distance field.
Distances are only required to calculate the position from a single point and are ignored for cross bearing calculations.
By default the distance is entered in nautical miles, but different units of length can be used as well. A space between the number and unit is optional; if no unit is entered nautical miles are assumed.
The following units can be used:
| Unit | Description |
|---|---|
| m | metres |
| km | kilometres |
| ft | feet |
| fth or ftm | fathoms |
| fur | furlongs |
| mi | (statute) miles |
| nm | nautical miles |
| x or y | yards |
| c | cables |
Examples of valid entries:
| Entered value | Equivalent |
|---|---|
| 8.25 | 8.25 nautical miles |
| 3nm | 3 nautical miles |
| 1500 y | 1500 yards, or 0.74 nautical miles |
| 8c | 8 cables, or 0.8 nautical miles |
A white exclamation mark in a red circle at the far end of the field is shown when the entered distance isn't recognised.
If the point's marker is shown on the map, an area of equal distance will be drawn on the map for a valid distance.
The distance area will follow the great circleopen_in_new, so it might not appear as a perfect circle on the map.
Compass Correction
If one of the bearings, or if the ship's heading, is a magnetic bearing, the compass reading must be corrected to get a true north heading.
The correction consists of two parts, the magnetic deviationopen_in_newand the magnetic declinationopen_in_new.
The magnetic deviation is the error induced in a compass by local magnetic fields. Local magnetic fields are caused by magnetized iron, e.g. the ship's structure, and are independent of location.
Leave the Deviation field empty if the magnetic deviation is not known.
The magnetic declination, or magnetic variation, is the error induced in a compass by the earth's magnetic field. The earth's magnetic field varies over time and also depends on the location.
If the magnetic declination is not known Journey Plotter can calculate it.
The calculation for dates from 1900 onwards uses the 13th generation of International Geomagnetic Reference Fieldopen_in_newseries of models.
For dates before 1900 the GUFM1open_in_newmodel, a model based on geomagnetic secular variation from historical records between 1590 and 1990, is used.
By default the magnetic declination is calculated automatically. The mean position of the entered points is used for the location, but the date has to be selected manually.
Dates can be selected by clicking the ∨ button next to the date, which will show a calendar from which a date can be selected. Use the left or right arrows in the calendar header to change the displayed month, or click on the month and select a month from the menu that will be shown. Click on the year to select a year from the menu.
Alternatively, dates can be changed using the keyboard. First click on part of the date, i.e. day, month or year, and use the Up, Down, Page Up, Page Down, Home and End cursor keys of your keyboard to change the value. Use the Left and Right arrow keys to step through the parts of the date.
To enter the magnetic declination in the Declination field, or to have Journey Plotter calculate it at your discretion by clicking the Calculate button, disable the automatic calculation by clearing the Automatic check box.
Both the magnetic deviation and declination can be entered in decimal degrees, or degrees and decimal minutes, or degrees, minutes and decimal seconds. The ° (degrees), ' (minutes) and " (seconds) symbols are optional, but if not used a space separating the individual values is required.
Bearing lines shown on the map will be adjusted automatically when the compass correction changes.
Ship
For relative bearings the heading of the ship is required; in other cases it is used as an indication only.
The heading must be entered in the ship's Heading field, and can be entered in the same manner as earlier described for bearings.
To calculate the ship's position, select a calculation method from the list of methods. This list is dynamic, depending on the entered point information, and therefore one or more of the following methods can be used:
- Cross bearing Points 1, 2 and 3: calculate the position using the positions and bearings of all three points
- Cross bearing Points 1 and 2: calculate the position using the positions and bearings of Points 1 and 2
- Cross bearing Points 1 and 3: calculate the position using the positions and bearings of Points 1 and 3
- Cross bearing Points 2 and 3: calculate the position using the positions and bearings of Points 2 and 3
- Distance and bearing to Point 1: calculate the position using the position, bearing and distance of Point 1
- Distance and bearing to Point 2: calculate the position using the position, bearing and distance of Point 2
- Distance and bearing to Point 3: calculate the position using the position, bearing and distance of Point 3
Click the Calculate button to perform the selected calculation.
If the magnetic declination is set to automatic, you'll notice a warning message appear, asking whether the correct date is selected. The date is important for the magnetic declination; it varies over time, so the date has to be set before calculating the position.
The ship's position labelled Position will show the result of a successful position calculation, in the format set in the Map Options (see the Optionssection). Also a ship marker labelled "Ship" will be shown on the map. If a heading was entered, the ship marker will have an arrow pointing in the direction of the heading.
In the case of a three-point cross bearing an area is drawn on the map, indicating where the ship's position could be. The ship marker will be positioned at the mean position of this area. Optionally three intermediate cross points are shown, indicating the cross bearing positions of the corresponding points.
The ship's position labelled NHN will show the calculated position rounded to the selected number of decimals, and is primarily added for the naval-history.net open_in_new(NHN) editors. Also a marker labelled "Ship (NHN)" will be shown on the map to indicate the location of the rounded NHN position.
The number of decimals can be decreased or increased using the and buttons after the position.
The button will copy the NHN position to the clipboard, after which it can be pasted into the document being edited. The copy is in the standard naval-history.net open_in_newformat, e.g. Lat 50.70, Long 0.40.
Example of a calculated position using one point, bearing and distance.
Example of a calculated position using two points and bearings.
Example of a calculated position using three points and bearings.
The appearance of Position Tools points and areas on the map can be customised, and whether or not to show intermediate point markers for three-point cross bearings can be chosen in the Tools Options (see the Options section).
Check the Videos and Screenshotspage for a video showing some of the possibilities Position Tools and Gazetteer panes have to offer using examples taken from authentic log-books.