# Math lib (even in C or C++... nobody is perfect !)

I am looking for a function to calculate the barycentre of a point list
(GPS coordinates lat/lng) …

anybody aware of such lib or utility I could rewrite in Ruby ? bet it
doesn’t exist yet

thanks for any hint
joss

Hi!

Whenever I need to use a math lib in C, I use the GNU Scientific Library
(GSL): GSL - GNU Scientific Library - GNU Project - Free Software Foundation
However, no idea if it contains what you need…

cheers, Severin

Josselin schrieb:

On 2007-05-18 15:38:27 +0200, Severin Schoepke
[email protected] said:

Josselin schrieb:

I am looking for a function to calculate the barycentre of a point list
(GPS coordinates lat/lng) …

anybody aware of such lib or utility I could rewrite in Ruby ? bet it
doesn’t exist yet

thanks for any hint
joss

got it from a PHP script… translated into Ruby…

(d/180.0)*Math::PI
end
(r/Math::PI)*180
end

def self.gravity_center(placemarks)
sumx = 0.0
sumy = 0.0
sumz = 0.0

for placemark in placemarks do
# convert to radians
# convert spherical coordinate into cartesian
x = Math::cos(lat) * Math::sin(lon)
y = Math::cos(lat) * Math::cos(lon)
z = Math::sin(lat)
# sum the vectors
sumx += x
sumy += y
sumz += z
end

# convert cartesian coordinate back to spherical

meanz = sumz / placemarks.nitems
lon = rad2deg(Math::atan2(sumx, sumy))

meanx = sumx / placemarks.nitems
meany = sumy / placemarks.nitems
lat = rad2deg(Math::atan(meanz / Math::sqrt(meanx2 + meany2)))
return [lat, lon]
end