How to determine if a lat/lon pair is located inside of a shapefile polygon

Question

I am using the rgeo and rgeo-shapefile gems in my Rails 5 application. My goal is to load in a shapefile of neighborhoods and determine which neighborhood a latitude/longitude point is located within.

In their documentation they have this example.

require 'rgeo/shapefile'
name = "neighborhoods.shp"
RGeo::Shapefile::Reader.open(name) do |file|
  puts "File contains #{file.num_records} records."
  file.each do |record|
    puts "Record number #{record.index}:"
    puts "  Geometry: #{record.geometry.as_text}"
    puts "  Attributes: #{record.attributes.inspect}"
  end
  file.rewind
  record = file.next
  puts "First record geometry was: #{record.geometry.as_text}"
end

I'm not quite sure how to move from this example towards what I would like to do.

Answer 1

Use the #within? method.

point.within?(neighborhood)

The coordinate systems for the point and the neighborhood need to be the same. I believe its more efficient to use rectilinear projections for these types of operations but I've used them successfully in the past with WGS as well, though I remember I've gotten error messages for certain types of overlap-type queries in WGS/4326. #within? should work fine though.