From f809bb38c15a152b23d7a221669870a51e91fb74 Mon Sep 17 00:00:00 2001
From: PaulDoyle-DEFRA <97455399+PaulDoyle-DEFRA@users.noreply.github.com>
Date: Fri, 6 May 2022 08:50:04 +0100
Subject: [PATCH] Update README.md

Updates README.md to explain the need to add a leading zero for easting/northing input values which are short because they are located in the first row/column of the grid.
Refer to https://github.com/DEFRA/os-map-ref/issues/39
---
 README.md | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/README.md b/README.md
index 99c13f4..a612c02 100644
--- a/README.md
+++ b/README.md
@@ -51,6 +51,27 @@ location.northing      == 171043
 location.map_reference == 'ST 58801 71043'
 ```
 
+### Handling short easting/northing input values
+If the full input easting or northing value has fewer than six digits, for example a northing value for a location in the south of England, the input value should be left-zero-padded within the input string. For example:
+
+*Without* a leading zero on the northing input value, the map reference is for a location in Fife, Scotland:
+```ruby
+location = OsMapRef::Location.for '358801, 71043'
+
+location.easting       == 358801
+location.northing      == 710430
+location.map_reference == 'NO 58801 10430'
+```
+
+Whereas *with* a leading zero on the northing input value, the map reference is for a location in Dorset, England.
+```ruby
+location = OsMapRef::Location.for '358801, 071043'
+
+location.easting       == 358801
+location.northing      == 071043
+location.map_reference == 'SY 58801 71043'
+```
+
 ### From OS Map Reference to Longitude and Latitude
 
 If your end result needs to be longitude and latitude, you can combine the