Capability, Suitability & Climate Programme, ALC Soil Data
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2018-19 Soil Policy Evidence Programme Capability, Suitability & Climate Programme, ALC Soil Data Digitisation 5th March 2020 Report Code: CSCP01 Mae’r ddogfen yma hefyd ar gael yn y Gymraeg. This document is also available in Welsh. © Crown copyright 2020 WG41030 Capability, Suitability & Climate Programme ALC Soil Data Digitisation Prepared by: Caroline Keay Date: 05 March 2020 Capability, Suitability & Climate Programme ALC Soil Data Digitisation Contents 1 Introduction .................................................................................................................................... 1 2 Methods .......................................................................................................................................... 1 2.1 Data Scanning ............................................................................................................................ 1 2.2 Map Digitisation ......................................................................................................................... 1 2.3 Profile Data Digitisation ............................................................................................................. 2 2.4 Data Validation .......................................................................................................................... 4 APPENDIX A Context and Guidance (Written by Ian Rugg) ................................................................. 8 APPENDIX B Notes from Correspondence with Ian Rugg .................................................................. 16 Figure 1 Sample ALC Map - P011-15 Swansea - Parc Mawr ................................................................... 3 Table 1 Standardised Table for ALCTEXTURE .......................................................................................... 5 Table 2 Standardised Table for MOTTLES ............................................................................................... 6 Table 3 Standardised Table for Concretions ........................................................................................... 7 Table 4 Standardised Table for Calcareous ............................................................................................. 7 1 Introduction This project include the scanning and assessing of unpublished Welsh Government (WG) held soil data. These are mainly ALC survey reports from c.1977 – 2018. Each file was catalogued separately with a unique identifying case number. This information was at risk of loss with records missing and the knowledge to interpret it. The information was previously held in a web accessible format so could not be published for public download. The information is used in development management cases by planning authorities, but could also be used by researchers / projects using the soil property information. The data has been collected by the Welsh Government and its contractors in three phases: Pre-Revision Surveys (Pre 1989) Post-Revision Surveys (1989 – 2011) Commercial Surveys (Post 2011) Ian Rugg wrote a guide “ALC Predictive Map Scanning pre revision (7).pdf” which describes how the ALC mapping protocols changed over the periods. 2 Methods 2.1 Data Scanning The data was delivered to Cranfield in several batches, some in archive boxes containing folders for each survey plus some via a web dropbox service where the reports had already been scanned. The paper reports were scanned using the Bookeye book Scanner, which allows a user to present the reports one page at a time for scanning and then compiles them into a PDF document. The documents were named with the project case number and prefixes to indicate the type of material (“_Report” for the main report and “_Extras” for survey cards and any additional material held within the folder). Scanned Files Case folders: year/ALC000-99 – All the case reports were scanned and the pdf files are stored in individual folders. o Pre Rev Welsh Government o Post Rev Welsh Government o Post Rev Commercial 2.2 Map Digitisation The ALC survey maps were digitised from each report that had a map. Firstly the map pages were extracted from the PDF to JPG file(s). The map page images were then loaded into ArcGIS and georectified using any grids on the map, satellite imagery and the LPIS field boundary data to select suitable control points. WG had already digitised many of these maps and sent two files PostRev_data.shp and PreRev_data.shp. Where the maps already existed, the previously digitised maps were overlain with the georectified image to check accuracy, in some cases the line work appeared to have been corrupted and in these cases the maps were redigitised otherwise the linework and attribution were copied from the maps into the new standardised template. Only the ALC class was collected (any soil map unit or other data information was not collected). The 1 spreadsheet WG_ALC_MASTER_LIST.xlsx contains a list of the ALC projects, whether they were sent to Cranfield and notes of what data was digitised and captured). At the end of the digitisation process, the maps were merged into three layers in a geodatabase. GIS Files WG_ALC.gdb – this geodatabase holds the digitised ALC maps and profile data. WG_ALC_PreRev_survey; WG_ALC_PostRev_Survey and WG_ALC_Commercial_Survey: These maps contain the areas of each ALC case. WG_ALC_PreRev_data; WG_ALC_PostRev_data and WG_ALC_Commercial_data: These maps divide the cases by ALC class WG_ALC_PreRev_AUGER_SITE + AUGER_HOR + PIT_SITE + PIT_HOR + FORM_SITE + FORM_HOR WG_ALC_PostRev_AUGER_SITE + AUGER_HOR + PIT_SITE + PIT_HOR WG_ALC_Commercial_AUGER_SITE + AUGER_HOR + PIT_SITE + PIT_HOR WG_ALC_PROFILE_CLIMATE 2.3 Profile Data Digitisation The profile data was captured from the various scanned reports and field record cards. The data was captured for each attribute in the format it was originally recorded in order to preserve the decisions of the soil surveyor. This results in a multitude of formats and classifications which need interpolation by the reader. Some of this was due to changes over time in the ALC guidelines, soil texture classification and soil wetness assessment. Other issues related, for example, to variations in recording between surveyors and assessments marginal between two classes. Further detail is provided later in this report. For ALC purposes the texture, mottles, depth to gleying and depth to slowly-permeable information was subsequently reclassified into a standardised format while still retaining the original data. Spreadsheets WG_ALC_MASTER_LIST.xlsx – this spreadsheet lists all the report case no’s. It details when they were sent to Cranfield and whether they were scanned, the point locations and map data captured and the profile (augerbores and soilpits) data captured (see Table 1 for Summary). WG_ALC_PreRev_Profiles.xlsx; WG_ALC_Post_Rev_Profiles; WG_ALC_Commercial_Profiles – these spreadsheet contains the raw profile data for augers and soilpits as captured from the source documentation, this data has been loaded into the geodatabase. WG_ALC_POINTS_CLIMATE.xlsx – For every auger/pit location in the previous spreadsheets the climate data has been derived interpolated to the average altitude from the OS 50m grid. This data can be used in future to standardise the Wetness Class from the older Drainage classes. 2 Images A selection of jpg images have been created one for each case in the three categories. Figure 1 Sample ALC Map - P011-15 Swansea - Parc Mawr 3 Table 1 Count of ALC Studies and Captured Profile Data Measured Measured Cases Augers Soil Pits PSD OM Pre-Revision 187 5052 286 171 132 Post-Revision 208 5786 685 876 452 Commercial 73 2590 105 55 17 2.4 Data Validation The record information was left as collected from the source material, some attention was given to obvious typos and spelling errors but not necessarily consistently. Standardised fields were added for texture (ALCTEXTURE) and DRAINAGE characteristics (MOTTLES+CONCRETIONS+CALCAREOUS+COMMENTS ( wet, dry etc)) Where no location information was given the Easting and Northing of the site was set to 0,0. 4 Table 2 Standardised Table for ALCTEXTURE ALC texture texture description ALC texture texture description notation notation ASH ASH OHCL organic heavy clay loam C clay OHZCL organic heavy silty COAL COAL clay loam OLFS organic loamy fine sand COAL ASH COAL ASH OLMS organic loamy medium CS coarse sand sand CSL coarse sandy loam OMCL organic medium clay FS fine sand loam FSL fine sandy loam OMSL organic medium sandy silt loam FSZL fine sandy silt loam OMSL organic medium sandy GRAVEL GRAVEL loam GRITTY GRITTY OMSZL organic medium sandy HCL heavy clay loam silt loam OMZCL organic medium silty HZCL heavy silty clay loam clay loam IMPENETRABLE Auger stopped by OMZCL organic silty clay loam - ROCK bedrock OSCL organic sandy clay loam IMPENETRABLE Auger stopped by stones -OTHER or other restriction, OZC organic silty clay may not be total depth OZL organic silt loam of profile OC organic clay LCS loamy coarse sand OSC organic sandy clay LFS loamy fine sand P peat LMS loamy medium sand PL peaty loam LP loamy peat PS peaty sand MCL medium clay loam ROCK na MS medium sand SC sandy clay MSL medium sandy loam SCL sandy clay loam MSZL medium sandy silt loam SCL medium sandy loam MUDSTONE na SHALE na MZCL medium silty clay loam SILTSTONE na na na SLAG na OCS organic coarse sand SP sandy peat OFSL organic fine sandy loam SPOIL na OFSL organic loamy fine sand ZC silty clay OFSZL organic fine sandy silt ZL silt loam loam 5 Table 3 Standardised