| Gridding-Interpolation of satellite data [message #38148] |
Sat, 21 February 2004 16:37 |
mmccabe
Messages: 4
Registered: May 2003
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Junior Member |
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I always get nervous posting to this site for fear of asking a
particularly stupid question....well, here goes.
I'm using some satellite data and need to regrid the standard EASE
projection (around 25km resolution) onto a regular grid of my own
design - a 1/8th degree grid over the US. Previous postings have been
very helpful in assisting me in this.
I realise GRIDDATA and TRIANGULATE would do this no
problems...however, I have gaps in the global/continental data from
the overpasses which are causing me issues. The satellite scans leave
no-data values (assigned 8888) in between overpasses. However, I don't
see that GRIDDATA allows me to ignore these areas without affecting
the interpolated values around the 'edges' (areas between data and
no-data) i.e. values near the boundary of these, depending on the
interpolation routine employed, will be affected by the no-data
values. A post-interpolation mask, while getting rid of most of the
affected data - will still leave numerous edge effects significantly
different to the 'true' value.
I thought I might be able to set no-data values to !VALUES.F_NAN - but
GRIDDATA and TRIANGULATE don't handle this....basically I just want to
interpolate within those areas that have data and exclude from the
interpolation values I don't want so I don't significanly influence
the 'real' data. My aim is not so much to smooth or massage the raw
data - just regularly grid it.
Have I missed something completely fundamental or is it actually a bit
tricky.
Thanks in advance,
Matt
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