.. -*- coding: utf-8 -*- .. _LDAC_basics: ================================================ LDAC - Conversion from and to the ASCII format ================================================ .. note:: The concrete examples on this page use the LDAC catalogue `D1_r_sex.cat <../_static/D1_r_sex.cat>`_, the ASCII table `D1_r_part.asc <../_static/D1_r_part.asc>`_ and the configuration file `D1_r_asctoldac.conf <../_static/D1_r_asctoldac.conf>`_. A tar archive with the complete set of LDAC Tools example files is `here <../_static/LDAC_Tools_Examples.tgz>`_ The most basic operations with an LDAC catalogue are conversions from and to ASCII tables. The description on this page, together with :ref:`LDAC_concepts`, is sufficient for those who only want to transform an existing LDAC catalogue, but who do not want to use the format otherwise. LDAC to ASCII conversion ======================== To obtain an ASCII version of an LDAC table we use the program :command:`ldactoasc`: :: user$ ldactoasc > SYNTAX: ldactoasc -i Catalog1 Catalog2 [-t ] [-k keys] [options] Options are: -b (suppress printing of the banner) -r (Print the row number) -s (Print strings and arrays) -q (Quiet flag: defaulted to verbose!) user$ ldactoasc -s -i D1_r_sex.cat -t LDAC_OBJECTS # 1 NUMBER Running object number # 2 X_IMAGE Object position along x [pixel] # 3 Y_IMAGE Object position along y [pixel] # 4 A_IMAGE Profile RMS along major axis [pixel] # 5 B_IMAGE Profile RMS along minor axis [pixel] # 6 THETA_IMAGE Position angle (CCW/x) [deg] # 7 FLAGS Extraction flags # 8 FLUX_RADIUS Fraction-of-light radii [pixel] # 9 MAG_AUTO Kron-like elliptical aperture magnitude [mag] # 10 MAGERR_AUTO RMS error for AUTO magnitude [mag] # 11 FLUX_ISO Isophotal flux [count] # 12 FLUXERR_ISO RMS error for isophotal flux [count] # 13 MAG_ISO Isophotal magnitude [mag] # 14 MAGERR_ISO RMS error for isophotal magnitude [mag] # 15 MAG_APER Fixed aperture magnitude vector [mag] # 19 MAGERR_APER RMS error vector for fixed aperture mag. [mag] # 23 ALPHA_J2000 Right ascension of barycenter (J2000) [deg] # 24 DELTA_J2000 Declination of barycenter (J2000) [deg] # 25 A_WORLD Profile RMS along major axis (world units) [deg] # 26 B_WORLD Profile RMS along minor axis (world units) [deg] # 27 THETA_WORLD Position angle (CCW/world-x) [deg] # 28 CLASS_STAR S/G classifier output # 29 IMAFLAGS_ISO FLAG-image flags OR'ed over the iso. profile # 30 NIMAFLAGS_ISO Number of flagged pixels entering IMAFLAGS_ISO 1 1063.23 1.46569 1.88867 0.498216 ...... 2 3805.27 1.40545 0.981680 0.479890 ..... . . 100 2205.74 28.5372 1.49797 1.03572 ..... It is also possible to access only certain keys: :: user$ ldactoasc -s -i D1_r_sex.cat -t LDAC_OBJECTS -k X_IMAGE Y_IMAGE MAG_APER # 1 X_IMAGE Object position along x [pixel] # 2 Y_IMAGE Object position along y [pixel] # 3 MAG_APER Fixed aperture magnitude vector [mag] 1063.23 1.46569 27.5003 26.8671 26.7404 26.7300 3805.27 1.40545 27.8551 27.6437 27.6903 27.1868 4412.24 1.42108 28.1911 27.6672 27.6506 27.4137 user$ ldactoasc -s -i D1_r_sex.cat -t LDAC_OBJECTS -k X_IMAGE Y_IMAGE "MAG_APER(2)" # 1 X_IMAGE Object position along x [pixel] # 2 Y_IMAGE Object position along y [pixel] # 3 MAG_APER Fixed aperture magnitude vector [mag] 1063.23 1.46569 26.8671 3805.27 1.40545 27.6437 4412.24 1.42108 27.6672 .. note:: #. When dealing with *vector* or *string* :ref:`keytypes `, the '-s' option to :command:`ldactoasc` must be used! #. To access certain elements of a vector the syntax is as '-k "MAG_APER\ **(2)**\"' for the second element of MAG_APER. Note that you need to protect the expression 'MAG_APER(2)' from the shell by surrounding it with double quotes (parentheses are special shell characters!). ASCII to LDAC conversion ======================== To bring an ASCII catalogue to the LDAC format we use the :command:`asctoldac` tool: :: user$ less D1_r_part.asc 1 Object_1 1063.230000 1.465690 2.394140 2 Object_2 3805.270000 1.405450 1.444970 3 Object_3 4412.240000 1.421080 1.970170 4 Object_4 2058.430000 1.742440 1.875930 . . user$ asctoldac -i D1_r_part.asc -o D1_r_part_ldac.cat -t OBJECTS -c D1_r_asctoldac.conf ASCII table to Binary FITS table conversion Version: 0.6 (Aug 24 2010) 100 row(s) converted user$ ldacdesc -i D1_r_part_ldac.cat > Reading catalog(s) ------------------Catalog information---------------- Filename:..............D1_r_part_ldac.cat Number of segments:....3 ****** Table #1 Extension type:.........(Primary HDU) Extension name:......... ****** Table #2 Extension type:.........BINTABLE Extension name:.........OBJECTS Number of dimensions:...2 Number of elements:.....100 Number of data fields...6 Body size:..............8200 bytes ****** Table #3 Extension type:.........BINTABLE Extension name:.........FIELDS Number of dimensions:...2 Number of elements:.....1 Number of data fields...4 Body size:..............28 bytes > All done :command:`asctoldac` takes a configuration files specifying how to transfer individual ASCII columns to the LDAC format. See the file `D1_r_asctoldac.conf <../_static/D1_r_asctoldac.conf>`_ for further documentation. .. note:: #. It is currently *not* possible to create :ref:`vector keys ` with :command:`asctoldac` #. Traditionally object tables get the tablename *OBJECTS* in an LDAC catalogue. It always has an associated *FIELDS* table with it. See :ref:`LDAC_tables` for further information. .. include:: links.txt