View source for OR/16/010 Technical information

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{{OR/16/010}}
==Pre-requiste requirements==
To use the Infiltration SuDS Map, a computer with vector-based GIS software is required.

==Creation of the dataset ==
The component datasets are directly derived from the datasets listed in Table 6. The original datasets were modified to create the component datasets in one or more of the following ways:
: a)     polygons were reclassified with SuDS scores (scores used are stated in Tables 2 to 5) and those with identical attributes were merged
: b)     raster datasets with continuous numerical values were classified into intervals
: c)     polygons that were not relevant were not incorporated in the map

Resulting polygons were attributed with a score, a short description, a detailed description, an advice description layer identification (ID), where relevant, further information about the dataset. The only exception was the superficial thickness data layer, which was not attributed with a score classification.

The four summary maps were derived from the rasterised component datasets as shown in Figure 4. For each raster cell, the maximum score from the individual datasets was calculated and used to create the summary map.

{{clear}}[[Image:OR16010fig4.jpg|thumb|left|300px| '''Figure 4''' Flow diagram showing how data was used to create summary maps. PFM: Predominant flow mechanism.]]{{clear}}

==Scale ==
The Infiltration SuDS Map is produced for use at 1:50&nbsp;000 scale providing 50&nbsp;m ground resolution. A cell size of 50&nbsp;m is deemed reasonable given that 1:50&nbsp;000 geological linework has a cartographic accuracy of 50&nbsp;m. The mapping scales on which the original geological linework are based are shown in [[OR/16/010 Appendix | Appendix]].

==Field descriptions ==
{| class="wikitable"
|+ Table 7 Attribute table field descriptions
| '''FIELD NAME'''
| '''FIELD TYPE'''
| '''DESCRIPTION'''
|-
| LayerID
| String
| Layer name
|-
| Score
| Integer
| SuDS score
|-
| Short description
| String
| Short description of polygon attribute
|-
| Detailed  description
| String
| Detailed description of polygon attribute
|-
| Advice
| String
| Advice on action necessary
|}

==Dataset History==
The Infiltration SuDS Map was originally created and released in 2012. This report describes the second version of the map released in 2016. The methodology used to create the map remains the same; however a number of the source datasets have been re-released since the Infiltration SuDS Map was released and thus the new versions of these datasets are now incorporated. The changes to these datasets (permeability, predominant flow mechanism, geohazards, groundwater flooding and artificial ground) are a result of changes to the underlying DigMapGB-50 and other advances in methodology/understanding. A new version of the depth to water table dataset has been incorporated. This dataset has been completely revised and as a result you may notice some differences compared to the old dataset. Since the last release, the Environment Agency, and Natural Resources Wales, have released new versions of the source protection zone datasets and these are now incorporated.

==Coverage==
The data covers Great Britain, but not the Isle of Man. The source protection zone dataset does not have coverage in Scotland and hence queries will not return any data.

==Data_Format==
The ''Infiltration SuDS Map: Summary ''has been created as vector polygons, which are available in a range of GIS formats, including ArcGIS (.shp) and MapInfo (.tab).

A sample of the map is available at [http://www.bgs.ac.uk/products/hydrogeology/infiltrationSuds.html http://www.bgs.ac.uk/products/hydrogeology/infiltrationSuds.html].

==Limitations==
*  The Infiltration SuDS Map has been developed at 1:50&nbsp;000 scale and must not be used at larger scales.
* The Infiltration SuDS Map is based on, and limited to, an interpretation of the records in the possession of the British Geological Survey at the time the dataset was created.
* The search does NOT consider the suitability of sites with regard to previous land use, for example with regard to water quality issues that might arise as a result of infiltration through contaminated land and associated mobilisation of surface or subsurface contaminants.
* This dataset is NOT an alternative for a site investigation or for infiltration testing, either of which may reach a different conclusion.
* Site observations represent the properties of the ground more accurately than the data provided by the infiltration SuDS map.
* This dataset must NOT be used to justify the disposal of foul waste or grey water.
* This dataset considers only the subsurface beneath the search area and does NOT consider potential surface or subsurface impacts outside of that area.
* Other more specific and detailed ground instability information may be held by BGS, and an assessment of this could result in a different outcome.
* An indication of potential natural ground instability does not necessarily mean that a location will be affected by ground movement or subsidence. Such an assessment can only be made by inspection of the area by a qualified professional.
* Limitations associated with the individual datasets are highlighted in [[OR/16/010 What information does the dataset provide | What information does the dataset provide]].
* The dataset does not represent a complete list of factors that should be considered when designing infiltration SuDS. In particular, the dataset does not consider:
::*presence of contaminated land
::*potential for perched water tables
::*shallow mining hazards relating to coal mining
::*made ground, where not recorded, and
::*zones around private water supply boreholes that are susceptible to groundwater contamination
* The dataset may under-represent some hazards, in particular:
::*shallow mining hazards in areas that are not typically mined, or are subject to historical artisan mining
::*Landslide hazards in some coastal areas

            

[[category: OR/16/010 User guide for the infiltration SuDS map: summary | 07]]