Introduction.md

@@ -3,8 +3,8 @@ identifier information and to identify duplicate observations in the
 **International Comprehensive Ocean-Atmosphere Data Set** (ICOADS) marine data source. **BOLD** denotes an ICOADS variable name.
 
 ICOADS is the world most extensive surface marine meteorological data collection. 
-Contains ocean surface and atmospheric observations from the 1600's 
-to present and is still receiving more data every year. 
+Contains ocean surface and atmospheric observations from the late 1600's 
+to present and is updated every month with observations from near-real-time data streams. 
 The data base is made up of observation reports from many different sources, 
 there are several hundred combinations of the **DCK** (deck) and **SID** (sources) 
 flags that indicate the origin of the data. 
@@ -13,9 +13,9 @@ Typically, **DCK** indicates the type of data
  about the data system or format 
  (e.g. data stream extracted from the WMO global telecommunications systems, GIS). 
 
-Sometimes a single DCK is associated with a single SID, 
-sometimes a single DCK will contain several SID and vice versa, 
-leading to a number of duplicated entries of meteorological observations. 
+Sometimes a single **DCK** is associated with a single **SID**, 
+sometimes a single **DCK** will contain several **SID** and vice versa, 
+not all of the **DCK** and **SID** are independent so there can be duplicated reports which need to be identified and flagged. 
 
 Historically archives of marine data have been maintained by individual nations, 
 and often these were shared so that the same observations appear in the archives