[daip] Re: GPS data into aips

[Chris Flatters]

>   I have obtained some RINEX formatted GPS data that I would like to
> get into AIPS for the calibration of some data.  I see that LDGPS
> would like the data in CONAN format.  Is there a program which will do
> the conversion from RINEX to CONAN?

It won't take CONAN any more. LDGPS uses a KEYIN variant that we designed
for the VLBA (and has for at least a year or so). Rich Moeser
(rmoeser at nrao.edu) was working on a RINEX to LDGPS converter. I do not know
the current status of this: you will have to ask him.

Note that calibration by this route is critically dependent on knowing the
time offsets between the L1 and L2 signals for each satellite as well as
for the receiver. These are difficult to determine.

You should normally be better off retrieving the relevant IONEX maps from
CDDIS. The maps are archived in the anonymous ftp area at cddisa.gsfc.nasa.gov
in directory /gps/products/ionex/2000/<day> where <day> is the day of the
year and are in a form that can be used directly by the AIPS task TECOR
(after uncompressing) provided that your data do not cross UTC midnight. If
your data cross the midnight boundary then you need to do some tedious editing 
work to merge 2 IONEX files into a single IONEX file for TECOR. Each directory
at CDDIS will usually contain 4 different IONEX data sets; there is no reason
to prefer any particular model over the others.

	Chris Flatters
	cflatter at nrao.edu