1. Dataset location

The data archive has been deposited with the Archaeology Data Service.
HS2 Phase One: Heritage GIS Digital Archive: https://doi.org/10.5284/1113006
HS2 Phase One: Heritage GIS Digital Archive - Raster Data: https://doi.org/10.5284/1113005

Referee statement by Thomas Cromwell

2. Content of the dataset

High Speed Two (HS2) GIS data comprise both evaluation and mitigation spatial data from HS2 Phase One Historic Environment Programme.

For Archaeology Data Service (ADS) data deposition purposes, the HS2 Historic Environment GIS data has been divided into different GIS data packages, based on Area of Interests (AoI) along the line of the route. Each AoI is a 1km buffer around the boundary of a local authority.

According to the nature of historic environment surveys and activities data collection, there are five different GIS Schemas, each with their own datasets as follows:

• LSWSIs (Location Specific Written Scheme of Investigations), Project plans and their relating objectives and document lists, Intervention areas, Archaeological features, and Archaeological finds (Vector data and their relating tables);
• Geophysical Survey results (Raster data in RasterCatalog and TIFF format and their interpretation feature classes in Vector format);
• Cultural Heritage Settings (Vector data)
• Surface Collection survey results (Vector data)
• Remote Sensing survey results interpretations (Vector data)

Each GIS data package includes three folders:

• GIS data in ESRI ArcGIS GDB format
• GIS data in open format (Shapefile) to facilitate accessibility to those not equipped with ESRI GIS products;
• Guidance documents, including data licence (a Read Me text file), documents and instructions about how different GIS layers are related, and information regarding their domains and fields

HS2 prepare and send the GIS data packages to the ADS and line of route HERs (Historic Environment Records), every six months. The old revisions of data may then be superseded. The first GIS data deposited to ADS was transmitted in March 2021.

3. Background to the dataset

HS2's historic environment investigation programme is the largest ever undertaken in the UK, and it is revealing more than 10,000 years of British history, from prehistoric times through to World War Two. Phase One of High Speed Two (HS2) is being constructed using a hybrid Act 'High Speed Rail (London – West Midlands) Act 2017'. Accompanying the Act are the Environmental Minimum Requirements (EMRs), the overarching commitments by the Secretary of State to afford appropriate management and protection of people, communities and the natural, cultural and built environment (HS2 2017b). The Heritage Memorandum is one of the EMRs (HS2 2017c). It sets out how the historic environment will be addressed during the design and construction of Phase One of HS2.

To fulfil the commitment set out in the HS2 Heritage Memorandum, the Historic Environment Research and Delivery Strategy (HERDS) has been established for the fieldwork stage (HS2 2017d). HERDS sets out the project mechanisms for designing works, undertaking evaluation, delivering investigations, reporting, and archive deposition that will be adopted for the design and construction of Phase One of HS2. It presents a clear statement of objectives, standards and structure for the planning and implementation of historic environment works.

According to HERDS, a Building Information Management (BIM) approach and GIS are the key elements in the delivery of historic environment digital data, which enable:

• Historic environment elements and investigations to be created as HS2 project assets;
• A unique asset ID to be provided for each historic environment asset;
• The location and geometry of the archaeological investigations and historic environment assets to be recorded as spatial data (using GIS);
• Historic environment assets attribute table to be specified;
• The interrelationship and hierarchy between historic environment assets to be established.

4. Summary description

There are 30 different investigation activities in the HS2 historic environment programme, for which the delivery of their relating GIS data by contractors is mandatory. These GIS data deliverables are submitted and stored through five different GIS schemas, according to the nature and content of the evaluation/mitigation surveys.

The principal components of the HERDS GIS data are defined according to historic environment assets. These assets form the principal structure of the data which enable hierarchies and relationships to be established.

The HS2 historic environment assets hierarchy comprises five assets classes (two core asset classes and three primary classes of assets) (Figure 1).

1. Location Specific Written Scheme of Investigation (LS-WSI) as core assets are areas of land that largely are defined to meet construction needs, represented with polygon GIS layers.
2. Project Plans (PPs), as another class of core assets, are areas with specific packages of archaeological activities in order to achieve certain objectives of investigation e.g. a series of geophysical surveys, a building recording survey, archaeological excavation etc., which are all carried out within a boundary of a certain piece of land. Project Plans are represented with a polygon feature class; for each Project Plan, a unique asset ID as well as a 'site code' are allocated by HS2, which are recorded in dedicated fields in the project plans feature class.
3. Written Scheme of Investigation Interventions (WSI-Interventions), as a primary assets class, are the extents of single archaeological activities (e.g. borehole surveys, trial trenches), with their boundary also recorded as a polygon feature class.
4. Archaeological Features, as another primary assets class, are human-made, non-portable elements with a certain historical period, where their location and geometry are recorded in a polygon GIS feature class. For example, an intervention area with trial trenching activity type may uncover features such as postholes or ditches.
5. Archaeological Objects e.g. hand axes, coins or brooches, as another primary assets class, are found during archaeological investigations and their location is represented with points in a GIS feature class.

Aside from the above feature classes, the documents list and objective lists in gdb table formats have been deployed in HERDS GIS schemas, which enable linking GIS data to their relating reports (non-GIS data). Technically, reports and objectives of historic environment surveys and mitigations are all joined to their respective Project Plan polygon through a Project Plan's Unique Asset ID (UAID) field, which is a mutual attribute in those GIS layers. Also, 'Site Code' and 'HS2 Unique Asset ID (UAID)' as two crucial attributes embedded in the GIS datasets, play a significant role to create a relationship between HS2 historic environment GIS data and their associated physical and digital archive data.

5. Scope

The land required to be constructed in Phase One of HS2 along the route from London Euston to Birmingham and the West Midlands, is approximately 406 km² (40600 hectares) which is over 230 km (140 miles) long. The majority of the archaeological works were undertaken by the Enabling Works Contractors (EWCs) and their specialist supply chain. The route was divided into three areas for the enabling works – north, central, and south. Some archaeological works have been carried out by the Main Works Contractors (MWCs) and their specialist supply chain.

The line of route Local Authority Historic Environment Records (HERs) who were provided with the GIS data packages, according to their associated Areas of Interests (AoI), are listed in Table 1.

Table 1: The list of local authorities

1	Greater London
2	Buckinghamshire
3	Hertfordshire
4	Oxfordshire
5	Northamptonshire
6	Warwickshire and Solihull*
7	Birmingham
8	Staffordshire
9	Coventry
*Warwickshire HER oversees the HER in Solihull, therefore a single data package was created

6. Re-use potential

The GIS data generated from HS2 Phase One Historic Environment works provides an invaluable resource for future researchers of all types. This includes:

• As a reference source for Local Planning Authority (LPA) and HERs to inform decision-making;
• Research into the effectiveness of evaluation techniques;
• Comparative data for archaeological research across multiple periods;
• Lessons learnt from capturing, processing and archiving historic environment data on national infrastructure projects.

7. Relationship to other publications/archives

The creation of HS2's historic environment physical and digital archive is an integral part of the lasting legacy of the programme. HS2 will provide access to the artefacts and information in a variety of interesting ways through both publications and accessible archive that will enable people to learn about the story of a nation.

Digital Archive

The HS2 Phase One contractors were required to submit all the digital data generated during the undertaking of the historic environment programme in different reports and data formats. This HS2 digital archive will be made available to the public. The digital elements of the archive, including GIS data, is curated by the ADS, being the primary accredited digital repository for archaeological archives within the UK. This approach is supported by Historic England (HE). Three categories of HS2 digital archive are transmitted to the ADS.

• The historic environment survey and mitigation spatial data in GIS data packages, submitted according to HS2 Historic Environment GIS schemas and procedures, are assured and approved by a dedicated HS2 Heritage Data Manager, and submitted to the ADS directly via the HS2 Electronic Document Management System (EDMS).
• Online Access to the Index of Archaeological Investigations (OASIS) is an online mechanism for the recording of events impacting upon the historic environment within England. The system is hosted and maintained by the ADS. OASIS enables the recording of project-level metadata, and the uploading of project reports from all investigations undertaken within the historic environment arena. Relevant reports, location and extent of the physical archive will be recorded in the OASIS system, which will allow the ADS, HS2 Ltd and interested stakeholders to export metadata and reports. OASIS also develops effective links between the physical archive held by museums/repositories and the digital archive held by the ADS.
• Supplementary archaeological data, which sits behind those summary records and final reports, will also be deposited with the ADS for long-term preservation and dissemination (High Speed Two Ltd. 2023). Supplementary archaeological data is provided in a clear hierarchical directory (file folder) structure identified by the appropriate metadata and OASIS ID, and then divided into sensible data types and/or file formats. The main supplementary archaeological data types are images, CAD files, spreadsheets, raw geophysical data, Close-Range Photogrammetry (CRP), Reflectance Transformation Imaging (RTI), aerial survey (photographic), 3D laser scanning and Light Detection and Ranging data (LiDAR), medical imaging data, audio recording, and video recording.

Physical Archive

The HS2 historic environment physical archive (the artefacts and analogue records) will, where possible, be deposited locally with line-of-route museums according to their geographical collecting areas.

Acknowledgements

I am grateful to the HS2 Historic Environment Team, particularly Helen Wass, HS2 Heritage Lead, and Dr. John Halsted, Senior Historic Environment Manager, for their invaluable guidance and support. Helen Wass's expertise and insightful feedback, as well as Dr. John Halsted's extensive experience, have greatly influenced the direction and quality of this paper. I also appreciate the collective efforts of the entire HS2 Historic Environment Team and the encouragement from Michael Court, HS2 Historic Environment Lead. Their contributions have been instrumental in making this project a success

This dataset comprises a wide range of archaeological investigative techniques applied to the entire route of the HS2 train line from London to Birmingham (Phase One). The work includes geophysical surveys and other remote sensing, as well as more intrusive trial-trenching and open-area excavation. As such, it is a varied and complex dataset of great value.

At its core is the interactive map allowing access to the geophysical surveys and excavations, these latter prefaced with the research questions that set out the work. Copies of site reports can be found there, but access to site records including drawings, photos, and primary record sheets allows detailed examination not normally possible in published site reports alone. The geophysics comes as a range of GIS-compatible outputs based on a globally-defined set of metadata that enables cross-comparison.

The data harvested from HS2 offers an unprecedented slice through British archaeology, collected in one place in detail on a scale hitherto unknown. Not only can researchers examine the route at high level, they can also drill down to the individual site-created plans, photos, and record data allowing reinterpretation of the primary information. Even better, researchers can harvest elements of this raw data to aid targeted projects. It will be interesting to see how this wealth of new knowledge, available electronically, will affect the direction of British archaeology.