Michael R. Davis >
Geo-Spline >
Geo::Spline

Module Version: 0.16
Geo::Spline - Calculate geographic locations between GPS fixes.

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=>150.5300}; 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"; }

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

I did some simple Math (for an engineer with a math minor) to come up with these 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

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

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

Method returns a single point from a single time.

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

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);

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();

Integrate a better Lat, Lon to meter conversions.

Please send to the geo-perl email list.

I use a very rough conversion from degrees to meters and then back. It is accurate for short distances.

Michael R. Davis qw/perl michaelrdavis com/

Copyright (c) 2006 Michael R. Davis (mrdvt92)

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

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

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