	Putting all together
	Class Body Class AstroContext Class Ephemeris Exception handling Class diagrams In page "Class Organization", we saw the role of `Body` and `AstroContext`. Now we can see how frames, units and precision are taken into account.

Under construction ; does not contain reliable informations.

Class `Body`

Apart from its index, its coordinates and its coordinate expression, an object of class Body holds the units used to express its coordinates.
It is also used to store the ComputationException which may occur during the computation of its coordinates.

So here is how the Body class look lie :

The methods transforming cartesian to spherical coordinatesare handled by this class, as the result depends on units.

Class `AstroContext`

The signature of calcBodyCoords() is :

public void calcBodyCoords(int     frame, 
                           int     sphereCart, 
                           double  precision,
                           boolean velocities,
                           int[] units
                          ) throws JEphemException, AstroException

See the javadoc page for more details.

calcBodyCoord's job is :

for each of its bodies, call the right class to compute the coordinates for the given precision - order velocity computation if required.

Handle coordinate transformations to get to the required frame - transfom spherical / cartesian if necessary.

Order unit conversion before returning the results.

Class `Ephemeris`

jephem.astro.tools.Ephemeris is in charge of producing an ephemeris table.
It contains coordinates of several bodies, for several julian days.
This is a higher level class, which can use astronomical classes, but don't perform any astro computations. The Ephemeris constructor will build one AstroContext per julian day, and call their calcBodyCoords method.
To build an Ephemeris object, one must provide these informations :

int[]      bodyIndexes, 
double[]   JDs, 
int[]      whichCoords,
int[]      coordUnits,
int        frame,
int        sphereCart, 
double     precision

Exception Handling

During computation, two kinds of exceptions can be found :

Computation exceptions, thrown by classes implementing PlanetaryTheory (VSOP87, Pluto99 ...), when a computation is asked for a date not handled by a theory, or for a precision that can't be reached. When this happens a jephem.astro.solarsystem.ComputationException is stored in the corresponding Body. Note that planetary theories never throw ComputationExceptions.

Other exceptions, like I/O errors. When this occurs, a jephem.astro.AstroException is thrown

Class diagram

It is now possible complete the diagram presented in the page Class organization.

JEphem Presentation Ephemeris SkyMap Curve Date search Informatic Library Download Glossary About
	JEphem Ephemeris trail Putting all together

Class Body

Class AstroContext

Class Ephemeris

Exception Handling

Class diagram

Class `Body`

Class `AstroContext`

Class `Ephemeris`