GNU Astronomy Utilities


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12.3.32 Unit conversion library (units.h)

Datasets can contain values in various formats or units. The functions in this section are defined to facilitate the easy conversion between them and are declared in units.h. If there are certain conversions that are useful for your work, please get in touch.

Function:
int
gal_units_extract_decimal (char *convert, const char *delimiter, double *args, size_t n)

Parse the input convert string with a certain delimiter (for example, 01:23:45, where the delimiter is ":") as multiple numbers (for example, 1,23,45) and write them as an array in the space that args is pointing to. The expected number of values in the string is specified by the n argument (3 in the example above).

If the function succeeds, it will return 1, otherwise it will return 0 and the values may not be fully written into args. If the number of values parsed in the string is different from n, this function will fail.

Function:
double
gal_units_ra_to_degree (char *convert)

Convert the input Right Ascension (RA) string (in the format of hours, minutes and seconds either as _h_m_s or _:_:_) to degrees (a single floating point number).

Function:
double
gal_units_dec_to_degree (char *convert)

Convert the input Declination (Dec) string (in the format of degrees, arc-minutes and arc-seconds either as _d_m_s or _:_:_) to degrees (a single floating point number).

Function:
char *
gal_units_degree_to_ra (double decimal, int usecolon)

Convert the input Right Ascension (RA) degree (a single floating point number) to old/standard notation (in the format of hours, minutes and seconds of _h_m_s). If usecolon!=0, then the delimiters between the components will be colons: _:_:_.

Function:
char *
gal_units_degree_to_dec (double decimal, int usecolon)

Convert the input Declination (Dec) degree (a single floating point number) to old/standard notation (in the format of degrees, arc-minutes and arc-seconds of _d_m_s). If usecolon!=0, then the delimiters between the components will be colons: _:_:_.

Function:
double
gal_units_counts_to_mag (double counts, double zeropoint)

Convert counts to magnitudes through the given zero point. For more on the equation, see Brightness, Flux, Magnitude and Surface brightness.

Function:
double
gal_units_mag_to_counts (double mag, double zeropoint)

Convert magnitudes to counts through the given zero point. For more on the equation, see Brightness, Flux, Magnitude and Surface brightness.

Function:
double
gal_units_mag_to_sb (double mag, double area_arcsec2)

Calculate the surface brightness of a given magnitude, over a certain area in units of arcsec\(^2\). For more on the equation, see Brightness, Flux, Magnitude and Surface brightness.

Function:
double
gal_units_sb_to_mag (double sb, double area_arcsec2)

Calculate the magnitude of a given surface brightness, over a certain area in units of arcsec\(^2\). For more on the equation, see Brightness, Flux, Magnitude and Surface brightness.

Function:
double
gal_units_counts_to_sb (double counts, double zeropoint_ab, double area_arcsec2)

Calculate the surface brightness of a given count level, over a certain area in units of arcsec\(^2\), assuming a certain AB zero point. For more on the equation, see Brightness, Flux, Magnitude and Surface brightness.

Function:
double
gal_units_sb_to_counts (double sb, double zeropoint_ab, double area_arcsec2)

Calculate the counts corresponding to a given surface brightness, over a certain area in units of arcsec\(^2\). For more on the equation, see Brightness, Flux, Magnitude and Surface brightness.

Function:
double
gal_units_counts_to_jy (double counts, double zeropoint_ab)

Convert counts to Janskys through an AB magnitude-based zero point. For more on the equation, see Brightness, Flux, Magnitude and Surface brightness.

Function:
double
gal_units_au_to_pc (double au)

Convert the input value (assumed to be in Astronomical Units) to Parsecs. For the conversion equation, see the description of au-to-pc operator in Arithmetic operators.

Function:
double
gal_units_pc_to_au (double pc)

Convert the input value (assumed to be in Parsecs) to Astronomical Units (AUs). For the conversion equation, see the description of au-to-pc operator in Arithmetic operators.

Function:
double
gal_units_ly_to_pc (double ly)

Convert the input value (assumed to be in Light-years) to Parsecs. For the conversion equation, see the description of ly-to-pc operator in Arithmetic operators.

Function:
double
gal_units_pc_to_ly (double pc)

Convert the input value (assumed to be in Parsecs) to Light-years. For the conversion equation, see the description of ly-to-pc operator in Arithmetic operators.

Function:
double
gal_units_ly_to_au (double ly)

Convert the input value (assumed to be in Light-years) to Astronomical Units. For the conversion equation, see the description of ly-to-pc operator in Arithmetic operators.

Function:
double
gal_units_au_to_ly (double au)

Convert the input value (assumed to be in Astronomical Units) to Light-years. For the conversion equation, see the description of ly-to-pc operator in Arithmetic operators.


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