Population 24/7 Download: User Guide. Purpose

Transcription

1 Population 24/7 Download: User Guide Purpose The Population 24/7 Download application is designed to enable a user to navigate around a map of England and Wales; select an area of interest represented by a rectangle on the map; choose a modelling scenario, age band, time and population count of interest and download corresponding model data in a specified GIS data format. The application provides an interface to exemplar population model results from the ESRC-funded Population 24/7: space-time specific population surface modelling project (Award Number RES ). Further information about the project can be obtained from the ESRC website at (which includes links to relevant methodological papers and presentations) and the project website at The award holders were David Martin, Samantha Cockings and Samuel Leung. Coding of the download interface was undertaken by Homme Zwaagstra and exemplar data preparation by Samuel Leung. The models were created using a custom-written software tool SurfaceBuilder247. Use of SurfaceBuilder247 requires preparation of an extensive input data library, hence the Population 24/7 Download application is intended to provide a simple interface to some selected model outputs without the necessity to set up and run SurfaceBuilder247. As the models incorporate data sourced from the ESRC Census Programme the application requires users to be registered with the census programme for use of 2001 census aggregate statistics and postcode directory datasets. User guide On entering the application, the user will be presented with a starting screen that looks like this: 1

2 Help text is provided in the central information box, which contains a summarised version of the information in this document, not including notes on the data. The information box can be closed by clicking on the X icon in the top right corner and can be viewed again by clicking on the i icon in the centre of the compass rose (top left). Navigation The user can navigate around the map using a mouse or the navigation arrows which form the compass rose. It is possible to zoom in and out with the mouse wheel or by double-clicking. Once zoomed in, the map can be panned by holding down the left mouse button and dragging. The + and icons also zoom in and out and the globe icon resets the map to its maximum extent. Note that the navigable extent of the map is restricted to England and Wales, which is also the limit of the modelled data available for download. Selecting your area of interest A rectangle on the map represents the extent of the data selected for download. This rectangle can be drawn by holding the shift key whilst left clicking with the mouse and dragging it across the map. Alternatively, the edit area tool (the [123] icon) may be used to specify the exact extent of the rectangle. Coordinates must be entered in British National Grid to 1m precision (6 digits for each of X and Y axes) and are initially populated with the extent of any existing rectangle. The coordinates of the current mouse position are always displayed at the bottom left of the map window in British National Grid coordinates. Selecting your criteria The selection of a dataset for download is controlled through a series of dropdown boxes across the top of the map. The dropdown boxes enable the user to select a combination of population scenario, age band, date, time of day and population count. The exemplar models are arranged as a series of scenarios, within which there are further options. For a specific application, it is recommended that the original SurfaceBuilder247 modelling program be run on a bespoke collection of input data files which match the users requirements. Clearly, there is an enormous number of possible combinations of dates, times and assumptions and these exemplar data therefore cover a small number of representative options. Five principal scenarios are available, for some of which multiple dates and times have been provided, as follows: Night time resident population 2001 (School Holiday Time, University Holiday Time). This is different to the 2001 census population basis as all students have been modelled to their term-time addresses. Night time resident population 2001 (School Term Time, University Term Time). This is the nearest equivalent to the 2001 census count with all population treated at their place of usual residence. Night time resident population 2006 (School Term Time, University Term Time). This is the equivalent of the 2001 census count, but modelled using 2006 mid-year estimate data. Work, Education and Health (LFS) (School Term Time, University Term Time). In addition to residential locations, this allocates population to locations of employment, education and 2

3 health care using working time profiles derived from the Quarterly Labour Force Survey by industrial classification. Work, Education and Health (School Term Time, University Term Time). This allocates population to locations of employment, education and health care using a simple 9am-5pm working day assumption. Once a scenario has been chosen, a population count must be selected. The exemplar modelling runs were based on treating separately each of seven population sub-groups, as follows. These are essentially based on age, but it has been necessary to subdivide the population aged by activity patterns rather than by age, in order to treat separately those attending sixth form education, higher education and in the workforce: 0 to 3 years 4 to 10 years 11 to 15 years 65 and over College students Higher education students Working age not studying Once the scenario and target population group has been specified, a date and time should be chosen. The dates and times available are dependent on the scenario (e.g. only a term-time reference date can been used for a term-time model, etc.) The modelled dates are Wednesday 18 April 2001 (term time); Wednesday 25 July 2001 (holiday time); Tuesday 18 April 2006 (term time), Saturday 22 April 2006 (representative weekend day). Reference times are 00:00, 09:00 and 14:00. Choosing data for download In specifying the data for download, several model outputs and formats can be selected. These reflect the intermediate outputs of the SurfaceBuilder247 modelling software. Origin spread. This represents the population spread around origin (residential) centroid locations. Origin immobile. This represents the population who remain at residential locations and are not moved by the modelling algorithm (e.g. prisoners). Destination spread. This represents the population spread around destination (e.g. workplace, education) locations. In travel. This represents the population considered to be in the transportation system at the modelled time. Total. This represents the total population distribution at the modelled time and for most purposes will be the most useful download. Note that the total here refers only to the total of the specified population sub-group. Seven groups would need to be downloaded and added together in order to map the entire population distribution. The data may be downloaded in three formats. These enable the data to be used in typical GIS applications, although the XYZ format can also be opened in a spreadsheet program. When a format is chosen, the application will provide a rough estimate of the size of the prospective download in 3

4 the Create download button. Clicking this button will initiate the generation of the data. A progress bar provides feedback during the generation of larger datasets. Users should be aware that potential download sizes are very large and it is strongly advised to download a small set of sample data first in order to ensure that the output format is acceptable and the data suitable for the intended purpose. At the end of this process, data are available as a compressed zip file. In addition to the data files, for those data formats that do not support directly embedding the coordinate reference system, an additional file with the extension.aux.xml is present and represents the British National Grid coordinate system for use in GIS applications. Example In the following example, a geographical extent has been chosen representing a 50km x 50km window covering Southampton and the New Forest. The coordinates were entered into the edit area tool as shown below and will then be represented by the shaded area on the following map screen. The map screen on the following page shows this area highlighted and dropdown box options chosen to select the Work, Education and Health (LFS) (School Term Time, University Term Time) scenario for the population of working age who are not studying. Four reference times and dates are available for this dataset and, of these, on Tuesday 18 April 2006 has been chosen. The total population in this sub-group will be downloaded in X,Y,Z ascii format and the estimated download size is 164kb. The data downloaded will thus be an ascii format file with three fields per record, showing X, Y coordinate values and Z values, the latter representing the estimated population of working age not studying who are estimated to have been present in each 200m x 200m grid cell under the specified modelling scenario, time and date. Note that there are many population flows which are not represented by this example, most notably population engaged in retail and leisure activities as customers (rather than employees) and major international and interregional population flows. The SurfaceBuilder247 software includes functions to handle these types of adjustment but they have not been included in the exemplar model outputs. 4

5 Notes on exemplar models The exemplar models created using SurfaceBuilder247 are based on an extensive database of population centroid locations and associated information assembled by the project team. A simple overview is provided here, as the detailed modelling concepts and process are the subject of ongoing academic publication. Total population counts for 2001 models are based on 2001 census area statistics, those for 2006 are based on 2006 Mid Year Estimates (MYEs). Population locations for both periods are based on 2001 census output area (OA) centroids MYE data are provided at Lower layer Super Output Area (LSOA) level and have been allocated to OA centroid locations weighted down to the OA level using the 2006 National Statistics Postcode Directory (NSPD). Locations of employment in 2001 models are based on workplace counts from the 2001 census. Locations of employment in 2006 have been estimated using the 2006 Annual Business Inquiry data, also at LSOA level, split by according to a custom aggregation of eight industry groups and remodelled using the distribution of large user and small business locations identified in the NSPD and allocated to OAs. No original counts from any of the input sources are recoverable by analysis of the output layers. A background layer has been prepared using the Meridian layer from OS OpenData and Average Annual Daily Flow (AADF) traffic data from the Department for Transport s National Transport Model (NTM) in order to obtain initial weights for the location of population in transit between locations. Education and health locations are derived from the Neighbourhood Statistics Service, Edubase and various datasets within Hospital Episode Statistics databases. No school locations were available for Wales within this dataset. As we have subscribed to various data services in preparing our input data, we regret that we are unable to pass on most of our input data files to other researchers, who may nevertheless register themselves to access the same sources. 5

6 Data acknowledgements Office for National Statistics 2001 Census: Standard Area Statistics (England and Wales): ESRC Census Programme, Census Dissemination Unit, Mimas (University of Manchester). National Statistics Postcode Directory Data: Office for National Statistics, Postcode Directories: ESRC Census Programme, Census Geography Data Unit (UKBORDERS), EDINA (University of Edinburgh). Quarterly Labour Force Survey, Economic and Social Data Service, usage number Our employee data were obtained from the Annual Business Inquiry Service, National Online Manpower Information Service, licence NTC/ABI07-P3020. Meridian 2 v1.1 Release , Contains Ordnance Survey data Crown copyright and database right 2010; Hospital Episode Statistics Copyright 2010 Reused with the permission of The Health and Social Care Information Centre. All rights reserved The NHS Information Centre has suspended the application of re-use licence fees as a consequence of government policy ('Making Public Data Public'). National Transportation Model data Crown copyright, Great Britain Road Traffic Survey, DfT. Population 24/7 Download application credits Data model programming and web download application created by the GeoData Institute. Background map data OpenStreetMap contributors, CC-BY-SA. Contacts David Martin D.J.Martin@soton.ac.uk Samantha Cockings S.Cockings@soton.ac.uk Geography and Environment, University of Southampton, Southampton, SO17 1BJ, UK v1 6