| Re: map_set coastline data [message #33554 is a reply to message #33489] |
Wed, 08 January 2003 14:09   |
Liam E. Gumley
Messages: 378
Registered: January 2000
|
Senior Member |
|
|
"Mark Hadfield" <m.hadfield@niwa.co.nz> wrote in message
news:avi3pn$mgf$2@newsreader.mailgate.org...
> "paul wisehart" <wisehart@runbox.com> wrote in message
> news:slrnb1omah.3qf.wisehart@stingray.mcst.ssai.biz...
>> How do I get at the data that map_set uses
>> to plot coastline/continents?
>>
>> I can find the actual files on my machine, I
>> just don't know how to open them.
>
> I have a couple of routines to read these files and can send them to you
if
> you want.
>
> But, as Rick comments, there are better sources of coastline data. These
> days I use GSHHS:
>
> http://www.ngdc.noaa.gov/mgg/shorelines/gshhs.html
I've written a short procedure to plot the GSHHS binary data files. It's
available at
ftp://origin.ssec.wisc.edu/pub/gumley/IDL/gshhs/
The files required are plot_gshhs.pro and little_endian.pro (the GSHSS files
are stored in big-endian order). Here's a few examples:
IDL> window, /free, xs=800, ys=600
IDL> map_set
IDL> gshhs_plot, 'gshhs_l.b' ; Low resolution (5.0 km)
IDL> gshhs_plot, 'gshhs_l.b', /fill
IDL> map_set, 45, -90, scale=20e6
IDL> gshhs_plot, 'gshhs_i.b' ; Intermediate resolution (1.0 km)
IDL> gshhs_plot, 'gshhs_i.b', level=2
IDL> map_set, 25, -80, scale=4e6
IDL> gshhs_plot, 'gshhs_h.b' ; High resolution (0.2 km)
IDL> gshhs_plot, 'gshhs_h.b', level=3, /fill
The procedure could be made faster through by a smart indexing scheme: this
version always reads the entire file. But it does seem to do a reasonable
job, and it fixes some of the gross inaccuracies of the old CIA WDBII data
use by map_continents.pro.
Cheers,
Liam.
Practical IDL Programming
http://www.gumley.com/
|
|
|
|
comp.lang.idl-pvwave archive
Members
Search
Help
Login
Home
