121 lines
3.6 KiB
Perl
121 lines
3.6 KiB
Perl
#!/usr/bin/env perl
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use strict;
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use warnings;
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use HTTP::Tiny;
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use POSIX qw(strftime);
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use Text::ParseWords qw(parse_line);
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use URI::Escape qw(uri_escape);
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my ($lat, $lon, $outfile, $iso_date) = @ARGV;
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die usage() unless defined $lat && defined $lon;
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$outfile ||= "declination.txt";
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$iso_date ||= strftime("%Y-%m-%d", gmtime());
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die "Latitude must be numeric\n" unless $lat =~ /\A-?\d+(?:\.\d+)?\z/;
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die "Longitude must be numeric\n" unless $lon =~ /\A-?\d+(?:\.\d+)?\z/;
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die "Latitude out of range\n" unless $lat >= -90 && $lat <= 90;
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die "Longitude out of range\n" unless $lon >= -180 && $lon <= 180;
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die "Date must be YYYY-MM-DD\n" unless $iso_date =~ /\A(\d{4})-(\d{2})-(\d{2})\z/;
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my ($year, $month, $day) = ($1, $2, $3);
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my $base_url = "https://www.ngdc.noaa.gov/geomag-web/calculators/calculateDeclination";
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my %query = (
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lat1 => $lat,
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lon1 => $lon,
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model => "WMM",
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startYear => $year,
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startMonth => $month + 0,
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startDay => $day + 0,
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resultFormat => "csv",
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);
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my $url = $base_url . "?" . join("&",
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map { uri_escape($_) . "=" . uri_escape($query{$_}) } sort keys %query
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);
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my $http = HTTP::Tiny->new(
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agent => "microReticulum-ex22-declination-fetch/1.0",
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timeout => 30,
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verify_SSL => 1,
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);
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my $res = $http->get($url);
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die "HTTP request failed: $res->{status} $res->{reason}\n" unless $res->{success};
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my $body = $res->{content};
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my $declination = extract_declination_from_csv($body);
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$declination = extract_declination_from_text($body) unless defined $declination;
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die "Unable to parse declination from NOAA response\n" unless defined $declination;
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my $procured = format_procured_date($year, $month, $day);
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open my $fh, ">", $outfile or die "Cannot write $outfile: $!\n";
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print {$fh} "# procured: $procured\n";
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print {$fh} "# for coordinates: $lat, $lon\n";
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print {$fh} "# source: NOAA/NCEI geomagnetic declination calculator\n";
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print {$fh} "# date: $iso_date\n";
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print {$fh} "# sign convention: east positive, west negative\n";
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printf {$fh} "declination_deg=%.6f\n", $declination;
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close $fh or die "Cannot close $outfile: $!\n";
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print "Wrote $outfile\n";
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printf "declination_deg=%.6f\n", $declination;
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sub extract_declination_from_csv {
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my ($text) = @_;
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my @lines = grep { /\S/ } split /\r?\n/, $text;
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return undef unless @lines >= 2;
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my @header = parse_line(",", 0, $lines[0] // "");
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my $decl_idx;
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for my $i (0 .. $#header) {
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next unless defined $header[$i];
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if ($header[$i] =~ /\Adeclination\z/i) {
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$decl_idx = $i;
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last;
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}
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}
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return undef unless defined $decl_idx;
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for my $line (@lines[1 .. $#lines]) {
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my @fields = parse_line(",", 0, $line);
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next unless defined $fields[$decl_idx];
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my $value = $fields[$decl_idx];
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$value =~ s/^\s+|\s+$//g;
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$value =~ s/[^\d+.\-]//g;
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return $value + 0 if $value =~ /\A[+-]?\d+(?:\.\d+)?\z/;
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}
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return undef;
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}
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sub extract_declination_from_text {
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my ($text) = @_;
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return $1 + 0 if $text =~ /declination[^-+0-9]*([+-]?\d+(?:\.\d+)?)/i;
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return undef;
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}
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sub format_procured_date {
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my ($y, $m, $d) = @_;
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my @month_names = qw(
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January February March April May June
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July August September October November December
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);
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my $name = $month_names[$m - 1] // die "Invalid month\n";
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return sprintf("%s %d, %04d", $name, $d, $y);
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}
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sub usage {
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return <<"USAGE";
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Usage:
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fetch_declination.pl <latitude> <longitude> [outfile] [YYYY-MM-DD]
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Example:
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fetch_declination.pl 44.93642012667761 -123.02203699545396 declination.txt 2026-04-16
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USAGE
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}
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