localisedEstimate()

gistfile1.coffee

# localisedEstimate:
#   targetlngLat (Array|Object) = Containing the latLng you require a definition for
#                   Example: [9, 10]
#   surroundinglngLats (Array) = Local LngLats (objects) to be used when finding the value of target.
#                   Example: [{lng:9.21, lat:10.23, value:34}, {lng:8.5, lat:9.78, value:10}]
#   valueKey (String) = Key used for value in surroundinglngLats Objects.
#                   Example: 'NDWI'

localisedEstimate = (targetlngLat, surroundinglngLats, valueKey) ->

  valueKey = valueKey || 'value'

  if(!targetlngLat || !surroundinglngLats)
    false

  # Extract & Normalise Values
  targetlngLat = normaliseLngLat targetlngLat

  values = []
  for lngLat, i in surroundinglngLats
    values[i] = surroundinglngLats[i][valueKey]
    surroundinglngLats[i] = normaliseLngLat surroundinglngLats[i]

  # Find Distances

  distances = []
  greatestDistance = 0
  totalDistance = 0

  for lngLat, i in surroundinglngLats

    distances[i] = distance targetlngLat, surroundinglngLats[i]
    greatestDistance = distances[i] if distances[i] > greatestDistance
    totalDistance = totalDistance + distances[i]

  # Grade surroundinglngLats against closesed distance to target

  grades = []

  for tempDistance, i in distances
    grades[i] = tempDistance / totalDistance

  output = 0

  for grade, i in grades
    output = output + (grades[i] * values[i])

  output