A very rough and ready file for requesting elevation data in a square grid pattern from Google Maps

google-maps-elevation-request.js

const axios = require('axios');
const fs = require('fs')

const API_KEY = '[your google API key]'
const COMMA = '%2C'

const UNIT = 0.0001 // roughly 11.1 meters, +/- 5.55 m

const queue = makeLocations([55.9446035, -3.1940965], 10, UNIT * 8)
fs.writeFileSync('./data.csv', 'lat,lng,elevation\n')
dequeue()

// This this requests one location at a time, because the size of the request for all locations
// was too big and I didn't want to play around with finding the right chunk size that Google accepted
// but it wouldn't take too much work to shift a bunch of locations here and pipe-separate them, then
// to map through the results in `parseResponse`.
function dequeue() {
  const location = queue.shift()
  return makeRequest(location)
    .then(function (response) {
      const data = parseResponse(response.data)
      fs.appendFileSync('./data.csv', data)
      console.log(data)
      queue.length && dequeue()
    })
    .catch(function (error) {
      console.log(error);
    })
}

function makeRequest(location) {
  return axios({ method: 'get', url: makeUrl(location), headers: {} })
}

function makeLocations(center, size, step) {
  const minLat = center[0] - step * size / 2
  const minLng = center[1] - step * size / 2

  const locations = []
  for (let y = 0; y < size; y++) {
    for (let x = 0; x < size; x++) {
      locations.push(encodeLocation(minLat + x * step, minLng + y * step))
    }
  }
  return locations
}

function encodeLocation(lat, lng) {
  return `${lat}${COMMA}${lng}`
}

function makeUrl(location) {
  return `https://maps.googleapis.com/maps/api/elevation/json?locations=${location}&key=${API_KEY}`
}

function parseResponse(response) {
  const [{ location: { lat, lng }, elevation }] = response.results
  return `${[lat, lng, elevation].join(',')}\n`
}