latlong-ref-dist.json

{
    "name": "Lat/Long Distance from a reference point",
    "description": "Extends a dataset with the distance in meters between lat/long fields and a reference point.",
    "inputs": [
        {
            "name": "dataset-in",
            "type": "dataset-id",
            "description": "Dataset for extending with distance calculation."
        },
        {
            "name": "lat-field",
            "type": "string",
            "description": "The name/id of the latitude field."
        },
        {
            "name": "long-field",
            "type": "string",
            "description": "The name/id of the longitude field."
        },
        {
            "name": "lat-ref",
            "type": "number",
            "description": "The latitude of the reference point in signed degrees."
        },
        {
            "name": "long-ref",
            "type": "number",
            "description": "The longitude of the reference point in signed degrees."
        }
    ],
    "outputs": [
        {
            "name": "dataset-out",
            "type": "dataset-id",
            "description": "The ID of the extended dataset"
        }
    ]
}

latlong-ref-dist.whizzml

; Computes the distance between lat/long coordinates and a reference point
; All lat/long coordinates must be in signed degrees (no N/W/S/E etc)
(define (latlong-ref-dist dataset-in lat-field long-field lat-ref long-ref) 
  (create-and-wait-dataset {
    "origin_dataset" dataset-in 
    "new_fields" [ 
       {
        "field" ( flatline "( let ("
          "R 6371000 "
          "latA (to-radians {lat-ref}) "
          "latB (to-radians ( field {{lat-field}} ) ) "
          "latD ( - latB latA ) "
          "longD ( to-radians ( - ( field {{long-field}} ) {long-ref} ) ) "
          "a ( + ( square ( sin ( / latD 2 ) ) ) ( * (cos latA) (cos latB) (square ( sin ( / longD 2))) ) ) "
          "c ( * 2 ( asin ( min (list 1 (sqrt a)) ) ) ) ) " 
          "( * R c ) )" )
        "name" "Distance (m)"
       }
      ]
    }
  )
)

(define dataset-out (latlong-ref-dist dataset-in lat-field long-field lat-ref long-ref))