grab exif data from jpgs and emit geojson coordinates using ruby

exif-extract.rb

require 'json'
require 'base64'
require 'exifr'

def to_decimal(dms)
  dms[0].to_f + dms[1].to_f / 60 + dms[2].to_f / 3600
end

def to_geojson(exif)
  lat_exif = exif.gps_latitude
  lon_exif = exif.gps_longitude
  return "" unless lon_exif && lat_exif
  lon = to_decimal(lon_exif.map(&:to_f))
  lon = -lon if exif.gps_longitude_ref == "W"
  lat = to_decimal(lat_exif.map(&:to_f))
  lat = -lat if exif.gps_latitude_ref == "S"
  {
    :type => "Point", 
    :coordinates => [lon, lat]
  }
end

def format_attachment_gps(file)
  geometry, altitude = nil, nil
  body = File.read file
  r, w = IO.pipe
  w.write_nonblock(body)
  exif = EXIFR::JPEG.new(r)
  geometry = to_geojson(exif)
  altitude = exif.gps_altitude.to_f
  altitude = -altitude if exif.gps_altitude_ref.to_i < 0
  {geometry: geometry, altitude: altitude}
end

Dir.glob("*.jpg").each {|file| p format_attachment_gps(file)}