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# SWE-GLib
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SWE-GLib is a GLib style wrapper library around the [Swiss Ephemeris library](http://www.astro.com/swisseph/), created by Astrodienst.
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The source tree contains Astrodienst's (the writers/publishers of the Swiss Ephemeris library) ephemeride files, as requested by Alois Treindl of Astrodienst in a mail written to me on 24 July, 2013.
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## Usage
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For exact calculations, you need to create a GsweTimestamp object:
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```c
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GsweTimestamp *timestamp = gswe_timestamp_new_from_gregorian_full(1983, 3, 7, 11, 54, 45, 0, 1.0);
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```
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The GsweTimetamp object is used to convert dates between the Gregorian calendar dates and Julian Day values (not to be confused with Julian calendar dates!).
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Next, you have to create a GsweMoment object:
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```c
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GsweMoment *moment = gswe_moment_new_full(timestamp, 19.081599, 47.462485, 300.0, GSWE_HOUSE_PLACIDUS);
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```
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The GsweMoment object holds information of a given moment at a given place on earth. `gswe_moment_new_full()` requires a `GsweTimestamp` object, some geographical coordinates together with altitude above sea level (coordinates must be given in degrees, while altitude in meters!), and a house system to use.
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### About altitude
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The Swiss Ephemeris library requires the altitude value to be specified for several calculations. It also notifies how important it is:
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> the altitude above sea must be in meters. Neglecting the altitude can result in an error of about 2 arc seconds with the moon and at an altitude 3000m.
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2 arc seconds is about 0.000555 degrees of error, which is, well, kind of small. Of course, if you need very precise horoscopes, precise horoscopes; otherwise, it is safe to pass any value (well, that seems logical. The average level of all dry lands is about 840 meters; the average level of the whole planet Earth (including oceans and seas) is around 280 meters).
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## API stability
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The project is currently marked as 1.0. However, without further notice, the API should not be seen as stable.
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This means that some function prototypes may be modified in the near future. Mostly error handling routines are missing, so some functions will get a `GError **` parameter.
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Otherwise, the API is final, in term of future compatibility. New functions may be added later, though.
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