Document correlation set rebuilding process

* INSTALL: Add a new section documenting the way in which newer
correlation data sets can be rebuilt and substituted for officially
distributed copies.

diff --git a/INSTALL b/INSTALL
index 17eac87..6e64ce2 100644 (file)
--- a/INSTALL
+++ b/INSTALL
@@ -2,7 +2,7 @@
  Basic Unix Installation Instructions for the Weather Utility
 ==============================================================
 
  Basic Unix Installation Instructions for the Weather Utility
 ==============================================================
 

-:Copyright: (c) 2006-2012 Jeremy Stanley <fungi@yuggoth.org>. Permission
+:Copyright: (c) 2006-2014 Jeremy Stanley <fungi@yuggoth.org>. Permission

             to use, copy, modify, and distribute this software is
             granted under terms provided in the LICENSE file distributed
             with this software.
             to use, copy, modify, and distribute this software is
             granted under terms provided in the LICENSE file distributed
             with this software.


@@ -66,3 +66,41 @@ Manuals
 Optionally, the weather.1 and weatherrc.5 files can be placed in sane
 locations for TROFF/NROFF manual files on your system (for example,
 /usr/local/share/man/ or ~/man/).
 Optionally, the weather.1 and weatherrc.5 files can be placed in sane
 locations for TROFF/NROFF manual files on your system (for example,
 /usr/local/share/man/ or ~/man/).

+
+Updating Correlation Sets
+-------------------------
+The version control repository and tarballs are occasionally updated
+with refreshed correlation sets (the files which track what the nearest
+stations and weather zones are to various places). If you find you need
+to generate updated correlation sets yourself, however, it can be done.
+
+You'll need to retrieve the most recent source databases from the
+different sites mentioned in the comments at the top of a recent
+correlation data file--each one includes a comment block with a list of
+the origins and checksums of the data files used along with the date and
+time they were built. You'll also want to generate recent slist and
+zlist files (look at the comments at the top of each for the shell
+commands used to generate them). You probably also need the most recent
+overrides.conf from the weather source repository or tarball, since that
+contains known corrections for errors in the original data. Put all of
+these files in your current working directory and then call::
+
+    weather --build-sets
+
+Then wait, and wait, and wait some more. After loading and analyzing the
+source data, it will guess an upper-bound for the number of great-arc
+distance calculations it may have to perform and attempt to give you a
+progress bar indicating percent completion. If you're lucky, it will
+finish successfully also generate some automated quality assurance
+analysis of the results (mostly checking for obviously bad airports,
+stations, zones). If you are UNlucky, it will break, which is not
+terribly uncommon because the government-provided source data is often
+misformatted or gets sudden schema changes requiring updates to the
+parsing routines in weather.
+
+If you're using a system-wide (for example, distribution packaged) copy
+of weather and its data, you may want to place the new airports,
+stations, places, zctas and zones files into your ~/.weather directory
+and make use of the setpath configuration or command-line options to
+override where weather looks for them. See the weather(1) and
+weatherrc(5) manpages for details.