Astérix Th2001 Le Masque de Néfer
Coordinate CalculatorTM Java Applet
This Java applet is a very powerful tool for calculating location, bearing,
distance, time enroute, winds aloft, headings and more.
The Coordinate Calculator(tm) is very easy to use. Simply enter the
information you know in the appropriate input fields, and press [Enter] to
perform the calculation, and the answers appear in red.
The Coordinate Calculator has many built in formulas it goes through to
determine unknown values. Also, the given values are cross checked to make sure
all the information is consistent: for example, distance must equal the time
enroute times the ground speed. If values do not make sense, a 'consistency
error' is shown.
Much effort was expended to assure the accuracy of the calculations. The
great circle math routines (used for distance and bearing) are implemented from
Sodano's method, as also used by the FAA for determining routes. However, when
the distance being measured is less than 1.25 nautical miles, a standard X,Y
grid is used after properly scaling both the X and Y axis to the ellipsoid. The
X,Y technique is used because the great circle routines lose their accuracy for
these very short distances. The WGS 84 ellipsoid is also used for calculations.
The winds triangle calculations use simple trigonometry and do not account for
curviture of the earth. This should not be a problem with distances shorter than
||Holds the latitude of the Start or Dest. (destination) coordinate.
Unless specified, the latitude is assumed to be North. The value can be
entered in many different formats. All the following are valid and
represent the same longitude: N38 22.50 or N3822.50 or
N38 22 30 or 382230
||Holds the longitude of the Start or Dest. coordinat. Unless specified,
the longitude is assumed to be West. The following examples represent the
same longitude: W122 38.25 or W12238.25 or or W122 38 15 or
||This is the magnetic variation. Unfortunately, this applet does not
calculate the variation for you. It will automatically assume 0 if you
don't specify it.
||Distance between the Start and Dest. coordinates displayed in the
selected units. This value can also be calculated based on the ETE time
and Ground speed.
||True course between the Start and Dest. coordinates.
||Magnetic course. Adds the true course to the magnetic variation.
||Airspeed, in the selected units. Calculations for this value are based
on the wind triangle. If no wind triagle is specified, then Airspeed may
be set to the ground speed.
||Estimated Time Enroute. Calculations to obtain this value are based on
Distance/GroundSpeed. Values are to be entered with hours:minutes and
optional :seconds; e.g.; 1:45 or 1:45:00.
||Angle the wind is coming from, in magnetic degrees. All calculations
are based on the wind triangle. Warning: this value must be entered as
magnetic degrees. Weather stations usually report winds near the
surface (below 3000 feet AGL) in magnetic degrees, but winds aloft (at
3000 feet AGL & up) are usually reported in true degrees and must be
||Wind speed in the selected units. All calculations are based on the
||Wind Correction Angle in degrees. Calculations for this value are
based on the winds triangle or the difference between Mag.Course and
||Magnetic Heading (in degrees). This is the Magnetic Course with a
correction for winds.
Mag.Heading = Mag.Course + W.Correction.
||Ground speed in the selected units. Calculations for this value is
based on the wind triangle. |
||Select this button to perform a calculation based on the 'given'
(black) values. All currently calculated
(red) values are cleared for the new set of
calculated values. If any 'given' values are not formed correctly, an
appropriate error message is shown and input focus is given to the erred
value. You can also call 'Calculate' by pressing [Enter] when input focus
is on any input field. |
||Coordinate Format. Select this button to change the displayed format
of the latitude or longitude coordinate fields. This button does not
affect the format of how the coordinate is read in. One handy way to use
the coordinate format feature is for converting between different formats.
For example; you can enter a coordinate value in say Degree minutes and
seconds form (e.g., N38 25 30) and press Enter to convert it to Degrees
and decimal degree format (e.g., +38.42500 ).
||Changes the Distance and Speed units. Cylces between Nautical, Statute
and Metric units. This button also causes a calculation to be performed.