OR/14/045 Dataset integration: Difference between revisions
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Revision as of 14:23, 15 February 2016
| Price, S J, and Waters, C N. 2014. Model metadata report for Swansea-Neath-Port-Talbot. British Geological Survey Internal Report, OR/14/045. |
Borehole records were combined with 1:50 000 digital geological map data to create the 3D geological model.
Table 2 Summary of datasets used in the Swansea-Neath-Port-Talbot 3D geological model Dataset Comment DTM Derived from Ordnance Survey Landform Profile 5 m contours and spot heights using a cell size of 20 m. TIN created from file [swan_dtmgrid10k.asc]. Rockhead model A project specific geological rockhead model was used derived from manual construction and digitisation of rockhead contours drawn using topographical contours, spot heights and borehole records proving the base of superficial deposits. Rockhead model converted to TIN from file [first_rockhead_final]. Borehole data All boreholes selected from BGS’s Single Onshore Borehole Index (SOBI) and Borehole Geology (BOGE) corresponding to quarter sheets SS69NE, SS69SE, SS79NW and SS79SW and geological interpreter code DIS. Boreholes with missing start heights added manually by interpretation of Ordnance Survey Landform Profile 5 m contours and spot heights (see Appendix 1 - Changes to borehole start heights).
Boreholes with missing lithostratigraphical interpretation corrected or amended in two ways.
1. Corrected or amended in borehole geology file prior to modelling based on re-interpretation of borehole log and/or geological map.
2. Where re-interpretation was not possible, code UNKN was entered and resolved during 3D geological modelling. For the latter, the geological interpretation has not been back-populated in Borehole Geology. Lithostratigraphical interpretation changes listed in spreadsheets accompanying the metadata for the 3D geological model [NULL_LITHOSTRATIGRAPHY and NULL_LITHOSTRATIGRAPHY2].Lithological codes derived from the BOGE download were converted in to codes used for unlithified deposits following the procedures described in (Cooper et al., 2006[1]).
Elevation difference between DTM and borehole start elevation generally less than 1 m. Geological correlation undertaken on the basis of borehole start heights.
2009 boreholes and trial pits were recorded in 2002 in BGS’s Single Onshore Borehole Index (SOBI) database within quarter sheets SS69NE, SS69SE, SS79NW and SS79SW. A subset of 752 boreholes was selected for geological interpretation and digital coding to provide the basis for modelling the superficial deposits. 476 boreholes were considered for the creation of correlated cross- sections. The boreholes ranged in age from early 1900s to 2000 and were mainly derived from major road schemes and site investigations in the Swansea area. Consequently, many of the boreholes were arranged in linear transects across the area. Boreholes and trial pits are generally absent on the high ground north of Swansea and in the Crymlyn Bog area.
Map data Digital geological map Swansea Sheet 247, DigMapGB50. 2002 version. Ordnance Survey 1:50 000 scale topographical base map included. Photographs Field photographs illustrating the geomorphology of Quaternary deposits were considered.
References
- ↑ COOPER, A H, KESSLER, H, and FORD, J R. 2006. A revised scheme for coding unlithified deposits (also applicable to engineering soils). British Geological Survey, Internal Report, IR/05/123.