The results of the survey are initially at farm level and need to be grouped into geographic areas e.g. County, Local Government District and Ward. To do this we need to determine where the farm is located and allocate a grid reference.

The most reliable source of this data is the IACS (Integrated Administration and Control System) data collected by Defra's Regional Payments Agency (RPA). IACS is the European Union's farm subsidy data. When a farmers claim subsidies they provide a grid reference for the central point of each field. We will use one of these grid references for the farm after checking that it gives us a grid reference which relates to the parish the farm was allocated to when first registered. Note: From 2004, this data may be available through the new land register.

First we calculate the average grid reference (AGR) of all of the farm's IACS fields. In order of preference, we test this average grid reference (AGR) against the following conditions in order to select which field should be used to set the farm's grid reference:

1. The field which is closest to the average grid reference (AGR) and is in the same parish as the farm

• ¾ Parish Boundary
• Central grid reference of each field
• Average grid reference from all the fields
• The central grid reference of the field closest to the average grid reference of all fields (in this case it is in the same parish as the farm so this is the grid reference used)

As the central grid reference of the field closest to the average grid reference (AGR) of all fields is in the same parish as the one the farm has been allocated to, we will use this field's grid reference in the first instance.

If it is not in the same parish then we will try the following: -

2. The Field which is closest to the average grid reference (AGR) and is in the same ward as the farm

• ¾ Ward boundary
• Central grid reference of each field
• Average grid reference from all the fields
• The central grid reference of the field closest to the average grid reference of all fields (in this case it is in the same ward as the farm so this is the grid reference used)

As the central grid reference of the field closest to the average grid reference (AGR) of all fields is in the same ward as the one the farm has been allocated to, we will use this field's grid reference.

3. If the average field grid reference (AGR) is not in the same ward or parish as the holding - but is within 10 kilometres of the central point of the farms parish - we will use the field grid reference closest to this point. First we re-calculate the average grid reference as follows:

a. We ignore fields outside the farms parish, calculate the average grid reference for the fields within the parish and use the field grid reference closest to this point.
b. We ignore fields outside the farms ward, calculate the average grid reference for the fields within the ward and use the field grid reference closest to this point.

4. If the average field grid reference is not in the same ward or parish as the holding - but is within 15 kilometres of the central point of the farm's parish - we will use the field grid reference closest to this point, again re-calculating the average grid reference as described above.

Not all farms claim IACS payments so if we fail to get a grid reference from this then we look at RADX data. These are grid references that have been allocated to the farm in the past by Defra/MAFF. If they are in the same parish (or failing this ward) as the one the farm has been allocated to, then this is the grid reference used.

If still no grid reference can be found we look at the contact address for the farm. From the postcode it is possible to get a grid reference. The postcode is checked to make sure that is in the same parish or ward to which the farm has been allocated, as the contact address is not always at the same location as the farm.

For the remaining grid references we look to see if the farms have ever been given a grid reference in previous years and allocate this to them.

Finally, for those farms where no grid reference can be found a random grid reference is allocated to them from the same parish to which the farm has been allocated.

For more technical information, please see 'Grid ref generation - TechDoc'