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@komasaru komasaru/blh2ecef.rb
Created Feb 24, 2019

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Ruby script to convert WGS84(BLH) to ECEF coordinate.
#! /usr/local/bin/ruby
#---------------------------------------------------------------------------------
# BLH -> ECEF 変換
# : WGS84 の緯度(Beta)/経度(Lambda)/楕円体高(Height)を
# ECEF(Earth Centered Earth Fixed; 地球中心・地球固定直交座標系)座標に
# 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 ConvBlh2Ecef
USAGE = "[USAGE] ./blh2ecef.rb LATITUDE(BETA) LONGITUDE(LAMBDA) HEIGHT"
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
@blh = ARGV[0, 3].map(&:to_f)
end
# Execution
def exec
puts "BLH: LATITUDE(BETA) = %12.8f°" % @blh[0]
puts " LONGITUDE(LAMBDA) = %12.8f°" % @blh[1]
puts " HEIGHT = %7.3fm" % @blh[2]
ecef = blh2ecef(@blh)
puts "--->"
puts "ECEF: X = %12.3fm" % ecef[0]
puts " Y = %12.3fm" % ecef[1]
puts " Z = %12.3fm" % ecef[2]
rescue => e
msg = "[#{e.class}] #{e.message}\n"
e.backtrace.each { |tr| msg << "\t#{tr}\n" }
$stderr.puts msg
exit 1
end
private
# BLH -> ECEF 変換
#
# @param blh: BHL 座標 [latitude, longitude, height]
# @return ecef: ECEF 座標 [x, y, z]
def blh2ecef(blh)
lat, lon, ht = blh
n = lambda do |x|
s = Math.sin(x * PI_180)
A / Math.sqrt(1.0 - E2 * s * s)
end
x = (n.call(lat) + ht) \
* Math.cos(lat * PI_180) \
* Math.cos(lon * PI_180)
y = (n.call(lat) + ht) \
* Math.cos(lat * PI_180) \
* Math.sin(lon * PI_180)
z = (n.call(lat) * (1.0 - E2) + ht) \
* Math.sin(lat * PI_180)
return [x, y, z]
rescue => e
raise
end
end
ConvBlh2Ecef.new.exec if __FILE__ == $0
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