Hi Ken and Alexander,

I didn't get a chance to examine your responses today, as I was spent most of the day implementing the suggestions from one of the other respondents. I eventually got it to work correctly. The biggest problem I had was extracting the elements out of the hash to write them out to the final output file. I eventually got there.

I will examine your suggestions on Monday

In the meantime, I have appended a couple of fields to the datasets you sent me to show you basically what I have.

The hash should contain:

Date, Time, all 5 remaining fields from gravity, all 4 remaining fields from magnetics, and three remaining fields from bathymetry.

Whilst the navigation should be the same in all three files, by putting them into the hash I can check that they are. If they are not essentially the same, then I know that a problem exists.

No further processing of the fields is done (ie addition, etc). They are just read from the hash and written in a specific format (MGD77) to an output file. With the work I did today, I think I can manage that. Where there are multiple navigations (most times),I have a hierarchy and select what I believe is the best for output (usually bathymetry).

Here is the updated file structure you sent me ( can't see how to make the attachment you did)

$ cat gravity

2010-10-01 00:00:03 lat1 long1 grav1 g_anom1 eotvos1

2010-10-02 00:00:05 lat2 long2 grav2 g_anom2 eotvos2

2010-10-03 00:00:07 lat3 long3 grav3 g_anom3 eotvos3

$ cat magnetics

2010-10-02 00:00:05 lat2 long2 mag1 m_anom1

2010-10-03 00:00:07 lat3 long3 mag2 m_anom2

2010-10-04 00:00:09 lat4 long4 mag3 m_anom3

$ cat bathymetry

2010-10-03 00:00:07 lat3 long3 bath1

2010-10-04 00:00:09 lat4 long4 bath2

2010-10-05 00:00:01 lat3 long3 bath3

Thanks once again

Mike