Re: [ferret_users] time axis definition and precision

[Martin Schmidt <martin.schmidt@xxxxxxxxxxxxxxxxx>]

Peter,
I had the same problem several times.

To read daily data with a period of 1 s from a file, where times have 
the form

2008-02-19 00:00:00
2008-02-19 00:00:01
...

I do the following:
let offset = DAYS1900 ( 2008, 1, 1)
define axis/x/x=1:86400:1 xax
define grid/x=xax xg
COLUMNS/deli=" "/grid=xg $1
let v1o=v1-offset
define axis/t/from_data/t0=1-jan-2008/unit=days time=v1o+v2/24 + 1e-5
define grid/t=time tgrid

From now on things work well.     

Two things are needed, the offset to keep the time values limited and 
the 1.e-5. Otherwise I get the same error message as you have got.

There are several show-ups of single precision limitations:
- long time axes with small time periods
- strong zooming of other axes, which gives occasionally good looking 
but wrong plots
- seawater thermodynamics, i.e. relations between salinity, temperature 
pressure and conductivity and so on ...

Greetings,
Martin