Technical Information

The following content details the technical specifications of the GIS data, including licensing, data format, metadata, and data accuracy.

Technical Information

Data Licensing

A data licence will need to be agreed before the data may be downloaded. The licence will ask you to accept certain terms and conditions  attached to the use of the data.

Data Format

All of the datasets are available for download in either MapInfo .Tab or ESRI .shp format.

Metadata

All of the datasets supplied will be accompanied by metadata detailing scale/resolution, date of capture, attribution notes etc. CCW has adopted the ISO 19115 metadata standard, and the metadata, which is distributed with the GIS data, was generated using the MetaGenie v2 software. This is available at the Association for Geographic Information’s GIGateway.

Data Accuracy

• Boundary
  The boundary of the Site defines the extent of the area of Protected land. There may be excluded areas within the Site boundary.
  
  The Site boundary may follow a feature mapped on the Ordnance Survey (OS) map, such as a hedge or stream, or it may be 'undefined'. It may follow a feature such as the Mean Low Water mark, which is liable to change.
  
  
• Basic Scale of Data Capture
  Most sites have been digitised using the OS Landline 1:2500 or to the OS 1:10000 digital raster as a guide.
  
  This information is attributed in the data tables.Using the data, for mapping, or in a GIS, at scales other than those above may result in unpredictable results.
  
  
• Coordinate Systems
  The data is captured using the Cartesian coordinate system on the British National Grid.
  
  
• Accuracy of Digitised Line
  When OS Landline has been used to capture data against it is snapped to each node, where appropriate.
  
  Then data is captured against against OS 1:10000 raster, the aim is +- 0.2 mm, based on the old cartographic drawing standard in the days of pen and ink, which translates to 0.5 metres on the ground when used to produce maps at 1:2500 scale.
  
  
• Quality Assurance
  Digitisation is carried out using controlled environments to ensure correct topology. Plots are made and checked against source material.
  
  
• Positional Accuracy Improvement (PAI)
  Currently our Protected sites datasets have not been corrected to meet the PAI programme, later releases will be.
  
  For more details about PAI please see the Ordnance Survey website.