| Re: Digital Chart of World (WorldMap) [message #13692] |
Mon, 07 December 1998 00:00  |
Mark Hadfield
Messages: 783
Registered: May 1995
|
Senior Member |
|
|
Nando Iavarone wrote in message <36672204.665D0EDC@acsys.it>...
> Hi all,
> I need to access to the IDL database of DCW.
>
> Particularly I need a function returning a vector
> of lat/lon coordinates of a feature (e.g. rivers or coasts)
> in a region of interest,
In map_continents.pro, there is a function called MAP_GETINDEX which reads
the index data (position in file, number of points, lon/lat range for each
segment) in a map index file. The index files have names like
.../IDL52/resource/maps/high/*.ndx
.../IDL52/resource/maps/low/*.ndx
Attached is code for a function, MAP_GETDATA, which reads the lon/lat data
for a specified segment. The data files have names like
.../IDL52/resource/maps/high/*.dat
.../IDL52/resource/maps/low/*.dat
MAP_GETDATA calls FDECOMP from the IDL Astronomy Users Library
(http://idlastro.gsfc.nasa.gov/homepage.html)
To find all the segments for a specified ROI, you need to read in the index
data then search for lon/lat ranges that match the ROI. Unfortunately,
segments don't correspond very well to "features", ie a coastline or river
may be split into several segments.
--
Mark Hadfield, m.hadfield@niwa.cri.nz http://www.niwa.cri.nz/~hadfield/
National Institute for Water and Atmospheric Research
PO Box 14-901, Wellington, New Zealand
|
|
|
|
comp.lang.idl-pvwave archive
Members
Search
Help
Login
Home
