/ 
Geo-Spline-0.17
River stage zero No dependents
/ Geo::Spline

NAME

Geo::Spline - Calculate geographic locations between GPS fixes.

SYNOPSIS

use Geo::Spline;
my $p0 = {
          time    => 1160449100.67, #seconds
          lat     => 39.197807,     #degrees
          lon     => -77.263510,    #degrees
          speed   => 31.124,        #m/s
          heading => 144.8300,      #degrees clockwise from North
         };
my $p1 = {
          time    => 1160449225.66,
          lat     => 39.167718,
          lon     => -77.242278,
          speed   => 30.615,
          heading =>1 50.5300,
         };
my $spline = Geo::Spline->new($p0, $p1);
my %point  = $spline->point(1160449150);
print "Lat:", $point{"lat"}, ", Lon:", $point{"lon"}, "\n\n";

my @points = $spline->pointlist();
foreach (@points) {
  print "Lat:", $_->{"lat"}, ", Lon:", $_->{"lon"}, "\n";
}

DESCRIPTION

This program was developed to be able to calculate the position between two GPS fixes using a 2-dimensional 3rd order polynomial spline.

f(t)  = A + B(t-t0)  + C(t-t0)^2 + D(t-t0)^3 #position in X and Y
f'(t) = B + 2C(t-t0) + 3D(t-t0)^2            #velocity in X and Y

Formulas to calculate the unknowns from our knowns.

A = x0                                     # when (t-t0)=0 in f(t)
B = v0                                     # when (t-t0)=0 in f'(t)
C = (x1-A-B(t1-t0)-D(t1-t0)^3)/(t1-t0)^2   # solve for C from f(t)
C = (v1-B-3D(t1-t0)^2)/2(t1-t0)            # solve for C from f'(t)
D = (v1(t1-t0)+B(t1-t0)-2x1+2A)/(t1-t0)^3  # equate C=C then solve for D

CONSTRUCTOR

new

my $spline = Geo::Spline->new($p0, $p1);

initialize

METHODS

ellipsoid

Method to set or retrieve the current ellipsoid object. The ellipsoid is a Geo::Ellipsoids object.

my $ellipsoid=$obj->ellipsoid;  #Default is WGS84

$obj->ellipsoid('Clarke 1866'); #Built in ellipsoids from Geo::Ellipsoids
$obj->ellipsoid({a=>1});        #Custom Sphere 1 unit radius

ABCD

point

Method returns a single point from a single time.

my $point = $spline->point($t1);
my %point = $spline->point($t1);

pointlist

Method returns a list of points from a list of times.

my $list = $spline->pointlist($t1,$t2,$t3);
my @list = $spline->pointlist($t1,$t2,$t3);

timelist

Method returns a list of times (n+1). The default will return a list with an integer number of seconds between spline end points.

my $list = $spline->timelist($samples); 
my @list = $spline->timelist();

LIMITATIONS

The conversion from degrees to meters and then back is accurate for short distances.

AUTHOR

Michael R. Davis

LICENSE

Copyright (c) 2006-2025 Michael R. Davis

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

SEE ALSO

http://search.cpan.org/src/MRDVT/Geo-Spline-0.16/doc/spline.xls http://search.cpan.org/src/MRDVT/Geo-Spline-0.16/doc/spline.png

Math::Spline, Geo::Ellipsoids