diff --git a/src/Geodesy/Conversion/ConversionInterface.php b/src/Geodesy/Conversion/ConversionInterface.php
new file mode 100644
index 0000000..b9d0ced
--- /dev/null
+++ b/src/Geodesy/Conversion/ConversionInterface.php
@@ -0,0 +1,10 @@
+<?php
+
+namespace Geodesy\Distance;
+
+interface ConversionInterface
+{
+
+    public function convert();
+    
+}
diff --git a/src/Geodesy/Conversion/ECEF2LLA.php b/src/Geodesy/Conversion/ECEF2LLA.php
index 6c8883b..b8cad3d 100644
--- a/src/Geodesy/Conversion/ECEF2LLA.php
+++ b/src/Geodesy/Conversion/ECEF2LLA.php
@@ -5,7 +5,7 @@
 use Geodesy\Location\ECEF;
 use Geodesy\Location\LatLong;
 
-class ECEF2LLA extends BaseConversion
+class ECEF2LLA extends BaseConversion implements ConversionInterface
 {
 
     protected $ecef;
diff --git a/src/Geodesy/Conversion/LLA2ECEF.php b/src/Geodesy/Conversion/LLA2ECEF.php
index 90b86ca..10c24a0 100644
--- a/src/Geodesy/Conversion/LLA2ECEF.php
+++ b/src/Geodesy/Conversion/LLA2ECEF.php
@@ -5,7 +5,7 @@
 use Geodesy\Location\ECEF;
 use Geodesy\Location\LatLong;
 
-class LLA2ECEF extends BaseConversion
+class LLA2ECEF extends BaseConversion implements ConversionInterface
 {
 
 	protected $latlong;