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@komasaru komasaru/ecef2blh.rb
Created Feb 24, 2019

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Ruby script to convert ECEF to WGS84(BLH) coordinate.
#! /usr/local/bin/ruby
#---------------------------------------------------------------------------------
# ECEF -> BLH 変換
# : ECEF(Earth Centered Earth Fixed; 地球中心・地球固定直交座標系)座標を
# WGS84 の緯度(Latitude)/経度(Longitude)/楕円体高(Height)に変換する。
#
# Date Author Version
# 2019.02.19 mk-mode.com 1.00 新規作成
#
# Copyright(C) 2019 mk-mode.com All Rights Reserved.
#---------------------------------------------------------------------------------
#
class ConvEcef2Blh
USAGE = "[USAGE] ./ecef2blh.rb X Y Z"
PI_180 = Math::PI / 180.0
# WGS84 座標パラメータ
A = 6378137.0 # a(地球楕円体長半径(赤道面平均半径))
ONE_F = 298.257223563 # 1 / f(地球楕円体扁平率=(a - b) / a)
B = A * (1.0 - 1.0 / ONE_F) # b(地球楕円体短半径)
E2 = (1.0 / ONE_F) * (2 - (1.0 / ONE_F))
# e^2 = 2 * f - f * f
# = (a^2 - b^2) / a^2
ED2 = E2 * A * A / (B * B) # e'^2= (a^2 - b^2) / b^2
# Initialization
# * コマンドライン引数の取得
def initialize
if ARGV.size < 3
puts USAGE
exit
end
@ecef = ARGV[0, 3].map(&:to_f)
end
# Execution
def exec
puts "ECEF: X = %12.3fm" % @ecef[0]
puts " Y = %12.3fm" % @ecef[1]
puts " Z = %12.3fm" % @ecef[2]
blh = ecef2blh(@ecef)
puts "--->"
puts "BLH: LATITUDE(BETA) = %12.8f°" % blh[0]
puts " LONGITUDE(LAMBDA) = %12.8f°" % blh[1]
puts " HEIGHT = %12.3fm" % blh[2]
rescue => e
msg = "[#{e.class}] #{e.message}\n"
e.backtrace.each { |tr| msg << "\t#{tr}\n" }
$stderr.puts msg
exit 1
end
private
# ECEF -> BLH 変換
#
# @param ecef: ECEF 座標 [x, y, z]
# @return blh: BLH 座標 [latitude, longitude, height]
def ecef2blh(ecef)
x, y, z = ecef
n = lambda do |x|
s = Math.sin(x * PI_180)
A / Math.sqrt(1.0 - E2 * s * s)
end
p = Math.sqrt(x * x + y * y)
theta = Math.atan2(z * A, p * B) / PI_180
lat = Math.atan2(
z + ED2 * B * Math.sin(theta * PI_180)**3,
p - E2 * A * Math.cos(theta * PI_180)**3
) / PI_180
lon = Math.atan2(y, x) / PI_180
ht = (p / Math.cos(lat * PI_180)) - n.call(lat)
return [lat, lon, ht]
rescue => e
raise
end
end
ConvEcef2Blh.new.exec if __FILE__ == $0
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