**GHOST** (**G**lobally **H**armonised **O**bservational **S**urface **T**reatment) 
is a project dedicated to the harmonisation of global surface observations (most 
notably air quality pollutants) and metadata, for the purpose of faciliting a greater
quality of observational/model comparison in the atmospheric chemistry community.

Some of the unique features of **GHOST** are:       
*All relevant network provided numerical and textual metadata is standardised.    
*All metadata parameters are handled as dymnaically changing variables though time.  
*Reported measurement methodologies are referenced to a centrally compiled measurement methodology database, allowing the standardisation of measurement methodologies.  
*Network provided station classifications are carefully standardised.    
*All data is passed through numerous quality control tests, giving detailed quality assurance (QA) flags.  

The **documentation** directory contains detailed descriptions regarding the processing 
procedures undertaken, as well as detailed descriptions of each of the standardised 
metadata fields. The **GHOST** dataset has been explicitely designed to be used 
in coordination with the Evalation Tool (ET). The document: **using_GHOST_with_ET** 
explains how to use the **GHOST** dataset with the ET.

A summary of the networks currently processed and contained under the umbrella of **GHOST** 
are given here:

| **Network** | **Data range** | **Parameters** |
|   --------  |    --------    |    --------    |
|   **EBAS**  |   1970 - 2018  | sconcc, sconccl, sconcco, sconcec, sconchno3, sconcisop, sconcna, sconcnh3, sconcnh4, sconcno, sconcno2, sconcno3, sconco3, sconcoc, sconcso2, sconcso4|
|  **EIONET** |   2013 - 2018  |                |