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srtm

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A small library that provides a simple interface to query locations on the earth for elevation data from the NASA Shuttle Radar Topography Mission (SRTM)

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srtm lib source esa.ex
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lib/source/esa.ex 

defmodule SRTM.Source.ESA do

  use SRTM.Source

  @moduledoc false



  alias SRTM.Client



  @impl true

  def fetch(%Client{}, {lat, _lng}) when not (-56 < lat and lat < 60) do

    {:error, :out_of_bounds}

  end



  def fetch(%Client{client: client, cache_path: cache_path}, {lat, lng}) do

    url = "http://step.esa.int/auxdata/dem/SRTMGL1/#{name(lat, lng)}.SRTMGL1.hgt.zip"



    with {:ok, zipped_data} <- get(client, url),

         {:ok, [hgt_file]} <- unzip(zipped_data, cwd: cache_path) do

      {:ok, hgt_file}

    end

  end

end