Section 89 of the Environmental Protection Act (EPA) 1990 requires certain bodies to keep relevant land clear of litter and refuse, and roads clean, as far as practicable. One of the ways that this is being achieved in Scotland is to zone relevant land based on its potential for litter, which then determines how quickly an organisation must clean an area if it falls below the standard. Monitoring of litter in Scotland is being undertaken using the Litter Monitoring System, which is populated with land zoning data provided by the organisations.
Zero Waste Scotland contracted Exegesis to support Scottish local authorities in meeting the requirement for land zoning data. This involved:
- Providing practical technical advice to local authority staff on the use of GIS to zone land.
- Creating first cut spatial datasets of relevant land to be zoned.
- Processing data on behalf of local authorities in various ways.
- Supporting local authority staff as they determine and apply zones to their data.
- Quality assuring data and preparing it for the Litter Monitoring System.
Data processing was generally undertaken in the PostgreSQL extension PostGIS, using QGIS to view the data in PostGIS. Some processing was also undertaken in GRASS where this was beneficial, such as cleaning and removing small areas from the spatial data (using v.clean, especially the rmarea tool). Advice to local authority staff was tailored to their corporate GIS, mainly ESRI ArcGIS and Pitney Bowes MapInfo.
One of the requirements was that zoned land was split into 1,000 m² sample locations. Each sample location defined an area of land that could be surveyed as part of litter monitoring. Part of the support provided to local authorities was to run the pre-existing QGIS Polygon Divider plugin on supplied data to create the sample locations. This highlighted the need to enhance the Polygon Divider, which we undertook following discussion with Zero Waste Scotland. This included:
- The addition of an approach to split complex polygons into more manageable chunks to the Polygon Divider interface.
- Improved data handling to use memory more efficiently and reduce crashes and failures.
- Implementation of PostGIS compatibility.
- Improved message logging.
- Various minor bug fixes.
The changes to the Polygon Divider were submitted for inclusion in the released tool.
Further information from Mike Lush.