NAME
llsearch - Search a GNIS file for place names within a given block of
latitude/longitude
SYNOPSIS
llsearch [-L] | [latitude_low longitude_low latitude_high
longitude_high]
DESCRIPTION
The U.S. Geological Survey supports sites on the Internet with
Geographic Names Information System (GNIS) files. These files contain
lists of place names, complete with their latitude/longitude and other
information. There are separate files for each of the U.S. states, and
each file contains many, many, many place names. If you want to use
this data with drawmap, it is useful to reduce the data to only the
items that you need. Llsearch lets you filter a GNIS file and winnow
out only those place names that fall within the latitude/longitude
boundaries that you specify. (You may want to specify boundaries that
are a tiny bit larger than what you are interested in, so that
numerical quantization doesn’t eliminate locales that fall exactly on
your boundaries.)
Latitudes and longitudes are positive for north latitude and east
longitude, and negative for south latitude and west longitude.
Llsearch expects you to enter them in decimal degrees. (The latitudes
and longitudes in the GNIS file are in degrees-minutes-seconds format,
followed by ’N’, ’S’, ’E’, or ’W’. However, there are two available
file formats, and one of the formats also contains the
latitudes/longitudes in decimal degrees.) Typical usage is as follows:
gunzip -c california.gz | llsearch 33 -118 34 -117 >
gnis_santa_ana_west
If you enter the "-L" option, the program will print some license
information and exit.
Once you have reduced the data to some subset of interest, you can
search for particular items via the grep or perl commands, or other
search commands, or you can simply edit the results with your favorite
text editor. Search commands are useful in reducing the sheer volume
of data to a more manageable size (by extracting, say, all mountain
summits or all streams), but you will probably ultimately end up
looking through the remaining data manually. The individual records
contain codes, such as "ppl" for populated places, and "summit" for
mountain tops, that can help you pick and choose.
There is considerable redundancy in place names, and human intelligence
is useful in sorting things out. While I was writing drawmap and
llsearch, I frequently gazed out my office window, where I could spot
at least two, and possibly three Baldy Mountains. There are also quite
a few Beaver Creeks, Bear Canyons, Saddle Buttes, and Springfields out
there. By taking a close look at the information associated with each
place name, you can find the particular locations that interest you.
SEE ALSO
drawmap(1)
Jul 24, 2001