Class: OsMapRef::Location

Inherits:
Object
  • Object
show all
Defined in:
lib/os_map_ref/location.rb

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(args = {}) ⇒ Location

Returns a new instance of Location.



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# File 'lib/os_map_ref/location.rb', line 13

def initialize(args = {})
  @map_reference = args[:map_reference].freeze if args[:map_reference]
  @easting = remove_decimals(args[:easting]) if args[:easting]
  @northing = remove_decimals(args[:northing]) if args[:northing]
end

Class Method Details

.for(text) ⇒ Object 



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# File 'lib/os_map_ref/location.rb', line 8

def self.for(text)
  input_processor = InputProcessor.new(text)
  new input_processor.params
end

Instance Method Details

#build_map_reference ⇒ Object 



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# File 'lib/os_map_ref/location.rb', line 27

def build_map_reference
  [grid_reference_prefix, short_easting, short_northing].join(" ")
end

#chars_in_northing_start ⇒ Object 



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# File 'lib/os_map_ref/location.rb', line 51

def chars_in_northing_start
  long_northing? ? 2 : 1
end

#determine_prefix_coordinates ⇒ Object 



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# File 'lib/os_map_ref/location.rb', line 92

def determine_prefix_coordinates
  matrix.index(prefix) || raise_prefix_error(prefix)
end

#easting ⇒ Object 



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# File 'lib/os_map_ref/location.rb', line 59

def easting
  @easting ||= easting_from_map_reference
end

#easting_from_map_reference ⇒ Object 



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# File 'lib/os_map_ref/location.rb', line 71

def easting_from_map_reference
  prefix_coordinates[1].to_s + map_reference_parts[1]
end

#grid ⇒ Object

Grid of 100km squares as they are arranged over the UK. The grid is reversed so that the origin (0,0) is the bottom left corner (‘SV’).



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# File 'lib/os_map_ref/location.rb', line 107

def grid
  @grid ||= [
    %w[HL HM HN HO HP JL JM JN JO JP],
    %w[HQ HR HS HT HU JQ JR JS JT JU],
    %w[HV HW HX HY HZ JV JW JX JY JZ],
    %w[NA NB NC ND NE OA OB OC OD OE],
    %w[NF NG NH NJ NK OF OG OH OJ OK],
    %w[NL NM NN NO NP OL OM ON OO OP],
    %w[NQ NR NS NT NU OQ OR OS OT OU],
    %w[NV NW NX NY NZ OV OW OX OY OZ],
    %w[SA SB SC SD SE TA TB TC TD TE],
    %w[SF SG SH SJ SK TF TG TH TJ TK],
    %w[SL SM SN SO SP TL TM TN TO TP],
    %w[SQ SR SS ST SU TQ TR TS TT TU],
    %w[SV SW SX SY SZ TV TW TX TY TZ]
  ].reverse
end

#grid_easting ⇒ Object 



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# File 'lib/os_map_ref/location.rb', line 31

def grid_easting
  easting.to_s[0].to_i
end

#grid_northing ⇒ Object 



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# File 'lib/os_map_ref/location.rb', line 43

def grid_northing
  northing.to_s[0..(chars_in_northing_start - 1)].to_i
end

#grid_reference_prefix ⇒ Object 



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# File 'lib/os_map_ref/location.rb', line 55

def grid_reference_prefix
  grid[grid_northing][grid_easting]
end

#long_northing? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/os_map_ref/location.rb', line 39

def long_northing?
  northing.to_s.length >= 7
end

#map_reference ⇒ Object 



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# File 'lib/os_map_ref/location.rb', line 23

def map_reference
  @map_reference ||= build_map_reference.freeze
end

#map_reference_parts ⇒ Object

The parts should be a pair of letters then two sets of numbers ‘ST 58901 71053’ becomes [‘ST’, ‘58901’, ‘71053’]



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# File 'lib/os_map_ref/location.rb', line 77

def map_reference_parts
  @map_reference_parts ||= map_reference.split
end

#matrix ⇒ Object 



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# File 'lib/os_map_ref/location.rb', line 100

def matrix
  @matrix ||= Matrix[*grid]
end

#northing ⇒ Object 



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# File 'lib/os_map_ref/location.rb', line 63

def northing
  @northing ||= northing_from_map_reference
end

#northing_from_map_reference ⇒ Object 



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# File 'lib/os_map_ref/location.rb', line 67

def northing_from_map_reference
  prefix_coordinates[0].to_s + map_reference_parts[2]
end

#prefix ⇒ Object 



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# File 'lib/os_map_ref/location.rb', line 81

def prefix
  map_reference_parts[0]
end

#prefix_coordinates ⇒ Object

Returns array of [grid_northing, grid_easting] for the grid element matching the map reference prefix. So ‘ST 58901 71053’ will return [1, 3] which are the coordinates of the prefix ‘ST’ in the grid.



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# File 'lib/os_map_ref/location.rb', line 88

def prefix_coordinates
  @prefix_coordinates ||= determine_prefix_coordinates
end

#raise_prefix_error(prefix) ⇒ Object

Raises:



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# File 'lib/os_map_ref/location.rb', line 96

def raise_prefix_error(prefix)
  raise OsMapRef::Error, "Unable to process map reference #{@map_reference}: #{prefix} not found"
end

#remove_decimals(number) ⇒ Object 



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# File 'lib/os_map_ref/location.rb', line 19

def remove_decimals(number)
  number.to_s.sub(/\.\d*/, "")
end

#short_easting ⇒ Object 



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# File 'lib/os_map_ref/location.rb', line 35

def short_easting
  easting.to_s[1..-1]
end

#short_northing ⇒ Object 



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# File 'lib/os_map_ref/location.rb', line 47

def short_northing
  northing.to_s[chars_in_northing_start..-1]
end