llsearch(1) [debian man page]
LLSEARCH(1) General Commands Manual LLSEARCH(1) 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, fol- lowed by 'N', 'S', 'E', or 'W'. However, there are two available file formats, and one of the formats also contains the latitudes/longi- tudes 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 vol- ume 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 LLSEARCH(1)
Check Out this Related Man Page
BLOCKMEAN(l) BLOCKMEAN(l) NAME
blockmean - filter to block average (x,y,z) data by L2 norm SYNOPSIS
blockmean [ xyz[w]file(s) ] -Ix_inc[m|c][/y_inc[m|c]] -Rwest/east/south/north[r] [ -C ] [ -F ] [ -H[nrec] ] [ -L ] [ -S ] [ -V ] [ -W[io] ] [ -: ] [ -bi[s][n] ] [ -bo[s][n] ] DESCRIPTION
blockmean reads arbitrarily located (x,y,z) triples [or optionally weighted quadruples (x,y,z,w)] from standard input [or xyz[w]file(s)] and writes to standard output a mean position and value for every non-empty block in a grid region defined by the -R and -I arguments. Either blockmean, blockmedian, or blockmode should be used as a pre-processor before running surface to avoid aliasing short wavelengths. These routines are also generally useful for decimating or averaging (x,y,z) data. You can modify the precision of the output format by editing the D_FORMAT parameter in your .gmtdefaults file, or you may choose binary input and/or output using single or double precision storage. xyz[w]file(s) 3 [or 4] column ASCII file(s) [or binary, see -b] holding (x,y,z[,w]) data values. [w] is an optional weight for the data. If no file is specified, blockmean will read from standard input. -I x_inc [and optionally y_inc] is the grid spacing. Append m to indicate minutes or c to indicate seconds. -R west, east, south, and north specify the Region of interest. To specify boundaries in degrees and minutes [and seconds], use the dd:mm[:ss] format. Append r if lower left and upper right map coordinates are given instead of wesn. OPTIONS
-C Use the center of the block as the output location [Default uses the mean location]. -F Block centers have pixel registration. [Default: grid registration.] (Registrations are defined in GMT Cookbook Appendix B on grid file formats.) Each block is the locus of points nearest the grid value location. For example, with -R10/15/10/15 and and -I1: with the -F option 10 <= (x,y) < 11 is one of 25 blocks; without it 9.5 <= (x,y) < 10.5 is one of 36 blocks. -H Input file(s) has Header record(s). Number of header records can be changed by editing your .gmtdefaults file. If used, GMT default is 1 header record. Not used with binary data. -L Indicates that the x column contains longitudes, which may differ from the region in -R by [multiples of] 360 degrees [Default assumes no periodicity]. -S Report the sum of all z-values inside a block [Default reports mean value]. -V Selects verbose mode, which will send progress reports to stderr [Default runs "silently"]. -W Weighted modifier[s]. Unweighted input and output has 3 columns x,y,z; Weighted i/o has 4 columns x,y,z,w. Weights can be used in input to construct weighted mean values in blocks. Weight sums can be reported in output for later combining several runs, etc. Use -W for weighted i/o, -Wi for weighted input only, -Wo for weighted output only. [Default uses unweighted i/o] -: Toggles between (longitude,latitude) and (latitude,longitude) input/output. [Default is (longitude,latitude)]. Applies to geo- graphic coordinates only. -bi Selects binary input. Append s for single precision [Default is double]. Append n for the number of columns in the binary file(s). [Default is 3 (or 4 if -W is set)]. -bo Selects binary output. Append s for single precision [Default is double]. EXAMPLES
To find 5 by 5 minute block means from the ASCII data in hawaii.xyg, try blockmean hawaii.xyg -R198/208/18/25 -I5m > hawaii_5x5.xyg SEE ALSO
blockmedian(1gmt), blockmode(1gmt), gmtdefaults(1gmt), gmt(1gmt), nearneighbor(1gmt), surface(1gmt), triangulate(1gmt) 1 Jan 2004 BLOCKMEAN(l)