EphBpn

Introduction

This is the gem library which calculates ephemeris(Bias, Precession Nutation).

Installation

Add this line to your application's Gemfile:

gem 'eph_bpn'

And then execute:

$ bundle

Or install it yourself as:

$ gem install eph_bpn

Usage

Instantiation

require 'eph_bpn'

e = EphBpn.new("20160723")
e = EphBpn.new("20160723123456")
e = EphBpn.new

• You can set TDB formatted "YYYYMMDD" or "YYYYMMDDHHMMSS" as an argument.
• If you don't set an argument, this class considers the system time to have been set as an argument.

Calculation

pos_g   = [-0.50787065, 0.80728228, 0.34996714]  # GCRS Coordinate
pos_b   = e.apply_bias(pos_g)           # Apply Bias
pos_bp  = e.apply_bias_prec(pos_g)      # Apply Bias & Precession
pos_bpn = e.apply_bias_prec_nut(pos_g)  # Apply Bias & Precession & Nutation
pos_p   = e.apply_prec(pos_b)           # Apply Precession
pos_pn  = e.apply_prec_nut(pos_b)       # Apply Precession & Nutation
pos_n   = e.apply_nut(pos_p)            # Apply Nutation
puts "TDB: #{e.tdb}"                    #=> TDB: 2016-07-23 00:00:00 +0000
puts " JD: #{e.jd}"                     #=>  JD: 2457592.5
puts " JC: #{e.jc}"                     #=>  JC: 0.16557152635181382
puts "EPS: #{e.eps}"                    #=> EPS: 0.40905500411767176
p e.r_bias                              # Rotation matrix for Bias
p e.r_bias_prec                         # Rotation matrix for Bias & Precession
p e.r_bias_prec_nut                     # Rotation matrix for Bias & Precession & Nutation
p e.r_prec                              # Rotation matrix for Precession
p e.r_prec_nut                          # Rotation matrix for Precession & Nutation
p e.r_nut                               # Rotation matrix for Nutation
puts "SRC: #{pos_g}"                    #=> [-0.50787065, 0.80728228, 0.34996714]
puts "  B: #{pos_b}"                    #=> [-0.507870315369686, 0.8072824634004779, 0.34996720255697145]
puts " BP: #{pos_bp}"                   #=> [-0.5114184398598124, 0.805395337986056, 0.3491472536550768]
puts "BPN: #{pos_bpn}"                  #=> [-0.5114038678325663, 0.8054186649898355, 0.3491147860877318]
puts "  P: #{pos_p}"                    #=> [-0.5114180771311418, 0.8053955471104202, 0.34914730256926324]
puts " PN: #{pos_pn}"                   #=> [-0.5114035051003876, 0.8054188741108519, 0.34911483499021656]
puts "  N: #{pos_n}"                    #=> [-0.5114035051003876, 0.8054188741108514, 0.34911483499021656]

About alias:

• apply_bias => apply_b`
• apply_bias_prec => apply_bp`
• apply_bias_prec_nut => apply_bpn`
• apply_prec => apply_p`
• apply_prec_nut => apply_pn`
• apply_nut => apply_n`

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/komasaru/eph_bpn.

License

The gem is available as open source under the terms of the MIT License.