Instructions

1. Download CSV with rasters you want from USGS.
2. Convert CSV to JSON with something like http://www.csvjson.com/
3. Run script with `ruby usgs_downloader.rb path_to_json_file`
4. Sit back. 
5. ???
6. Receive slope analysis

usgs_downloader.rb

#! /usr/bin/env ruby

require 'json'

class USGSDownloader
  def self.process(filename='')

    if filename.empty?
      puts "You must pass the path to a json file as argument"
      return -1
    end

    unless File.exists?(filename)
      puts "Source file does not exists"
      return -1
    end

    new.process(rasters_metadata(filename))
  end

  def self.rasters_metadata(filename)
    JSON.parse(File.read(filename))
  end

  def process(metadatas)
    puts "Downloading #{metadatas.length} rasters\n\n"

    metadatas.each do |meta|
      download_raster(meta)
      unzip_raster(meta)
      reproject_raster
      analyze_reprojection

      delete_zip(meta)
      delete_tempdir_contents
    end
  end

  private


  def download_raster(meta)
    `wget #{download_url(meta)}`
  end

  def unzip_raster(meta)
    `unzip #{zip_filename(meta)} -d #{tempdir}`
  end

  def delete_zip(meta)
    `rm #{zip_filename(meta)}`
  end

  def reproject_raster
    puts "Reprojecting raster for: #{raster_name}"
    `gdalwarp -s_srs EPSG:4269 -t_srs EPSG:4326 #{raster_filename} #{reprojected_filename}`
  end

  def analyze_reprojection
    puts "Analyzing raster for: #{raster_name}"
    `gdaldem slope #{reprojected_filename} #{results_dir}/#{raster_name}_slope.tif`
  end

  def delete_tempdir_contents
    `rm -r #{tempdir}/*`
  end

  def tempdir
    Dir.mkdir('/tmp/usgs_dataset') unless Dir.exists?('/tmp/usgs_dataset')
    '/tmp/usgs_dataset'
  end

  def download_url(meta)
    meta["downloadURL"]
  end

  def results_dir
    Dir.mkdir("#{ENV['PWD']}/analysis") unless Dir.exists?("#{ENV['PWD']}/analysis")
    "#{ENV['PWD']}/analysis"
  end

  def raster_filename
    Dir.glob("#{tempdir}/*.img")[0]
  end

  def reprojected_filename
    "#{tempdir}/#{raster_name}_4326.tif"
  end

  def raster_name
    Regexp.new(/(n\d{2}w\d{3})/).match(raster_filename)[1]
  end

  def zip_filename(meta)
    Regexp.new(/IMG\/(.+\.zip)$/).match(download_url(meta))[1]
  end

  def raster_filename
    Dir.glob("/tmp/usgs_dataset/*.img")[0]
  end
end

USGSDownloader.process(ARGV[0])

usgs_mini.json

[
  {
    "sourceId": "581d213ae4b08da350d52d30",
    "extent": "1 x 1 degree",
    "sourceOriginName": "gda",
    "boundingBox": "{minY:30.9994444449061,minX:-90.0005555551941,maxY:32.0005555552955,maxX:-88.9994444448046}",
    "sizeInBytes": 376281338,
    "bestFitIndex": 0,
    "format": "IMG",
    "downloadURL": "https://prd-tnm.s3.amazonaws.com/StagedProducts/Elevation/13/IMG/USGS_NED_13_n32w090_IMG.zip",
    "previewGraphicURL": "https://prd-tnm.s3.amazonaws.com/StagedProducts/Elevation/13/IMG/USGS_NED_13_n32w090_IMG_thumb.jpg",
    "prettyFileSize": "358.85 MB",
    "datasets": "[National Elevation Dataset (NED) 1/3 arc-second,National Elevation Dataset (NED)]",
    "title": "USGS NED 1/3 arc-second n32w090 1 x 1 degree IMG 2016",
    "sourceOriginId": 8539703,
    "lastUpdated": "2016-11-12",
    "dateCreated": "2016-11-04",
    "metaUrl": "https://www.sciencebase.gov/catalog/item/581d213ae4b08da350d52d30",
    "sourceName": "ScienceBase",
    "publicationDate": "2016-10-07"
  },
  {
    "sourceId": "581d213ce4b08da350d52d89",
    "extent": "1 x 1 degree",
    "sourceOriginName": "gda",
    "boundingBox": "{minY:31.9994444447062,minX:-117.000555555194,maxY:33.0005555550957,maxX:-115.999444444805}",
    "sizeInBytes": 153988106,
    "bestFitIndex": 0,
    "format": "IMG",
    "downloadURL": "https://prd-tnm.s3.amazonaws.com/StagedProducts/Elevation/13/IMG/USGS_NED_13_n33w117_IMG.zip",
    "previewGraphicURL": "https://prd-tnm.s3.amazonaws.com/StagedProducts/Elevation/13/IMG/USGS_NED_13_n33w117_IMG_thumb.jpg",
    "prettyFileSize": "146.85 MB",
    "datasets": "[National Elevation Dataset (NED) 1/3 arc-second,National Elevation Dataset (NED)]",
    "title": "USGS NED 1/3 arc-second n33w117 1 x 1 degree IMG 2016",
    "sourceOriginId": 8268718,
    "lastUpdated": "2016-11-12",
    "dateCreated": "2016-11-04",
    "metaUrl": "https://www.sciencebase.gov/catalog/item/581d213ce4b08da350d52d89",
    "sourceName": "ScienceBase",
    "publicationDate": "2016-07-11"
  }
]