From 79f5be3609386ef9af51f75887c854485167f7e0 Mon Sep 17 00:00:00 2001
From: Eliot Sykes <eliotsykes@gmail.com>
Date: Sun, 30 Jun 2013 10:17:03 +0100
Subject: [PATCH] Add notes on accuracy and data types to README (issue #477)

https://github.com/alexreisner/geocoder/issues/477
---
 README.md | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/README.md b/README.md
index c5c6b552..f945d71c 100644
--- a/README.md
+++ b/README.md
@@ -36,6 +36,7 @@ Object Geocoding
 
 Your model must have two attributes (database columns) for storing latitude and longitude coordinates. By default they should be called `latitude` and `longitude` but this can be changed (see "Model Configuration" below):
 
+    # Numeric data types other than float are supported, see 'Data Types and Accuracy' section
     rails generate migration AddLatitudeAndLongitudeToModel latitude:float longitude:float
     rake db:migrate
 
@@ -604,6 +605,13 @@ When you install the Geocoder gem it adds a `geocode` command to your shell. You
 
 There are also a number of options for setting the geocoding API, key, and language, viewing the raw JSON reponse, and more. Please run `geocode -h` for details.
 
+Data Types and Accuracy
+-----------------------
+
+Geocoder works with any numeric column type (e.g. float, double, decimal) on which trig (and other mathematical) functions can be performed.
+
+A summary on the relationship between location accuracy and the number of decimal places in latitude and longitude degree values is available at http://en.wikipedia.org/wiki/Decimal_degrees#Accuracy (as an example, at the equator, degree values with 4 decimal places give about 11 metres accuracy, whereas 5 decimal places gives roughly 1 metre accuracy).
+
 Notes on MongoDB
 ----------------
 
-- 
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