It is a bad idea to choose the wrong map type for a planning or development need, because it will become obvious at the wrong time, usually when a council planning officer returns the planning application as incomplete or when a design team finds that the base map they use for their project does not have the information that they need for their stage of the project. The key to avoiding this unnecessary issue is to have a clear understanding of the types of maps offered and how they will meet the needs. Each of the CAD maps, location plans, DTM, and OS base has its own function, and if one is used in place of the other, it will have predictable failures.
Location Plans and Planning Submissions
The most frequently requested map in UK planning applications is a location plan. To identify the application site in its wider geographical context and to show the site boundary in relation to surrounding roads, buildings and landmarks at a scale which enables the planning officer to locate the site clearly. A location plan produced at a scale of either 1:1250 or 1:2500 scale from Ordnance Survey data, showing the application site boundary in red and other land in the ownership of the applicant in blue. This is a technical shortcoming that slows down applications when it is not produced from non-OS data or produced at an incorrect scale.
Site Plans and Their Distinct Function
The scale and detail required for a site plan are different from those for a location plan. A site plan is a plan of a site at 1:500 or 1:200 scale and, where a location plan is also available, is used to illustrate the specific development proposed, including existing and proposed features in sufficient detail for the planning authority to assess the development’s relationship to its immediate surroundings. A CAD map will be the exact map used to generate a compliant site plan. It will allow the positions of buildings, boundary relationships, and access arrangements to be shown at a level of accuracy that the planning authority can rely on.
CAD Maps for Design and Technical Work
Once planning is no longer in its submission phase but in the design and technical study phase, a CAD map is the right basis. It is integrated with design software, has a layered structure, and is accurate enough for architects to create site layouts, engineers to check drainage and infrastructure, and surveyors to create measured surveys that need to be tied to a dependable ground reference. Whether a CAD map or print-out of the plan is needed depends on the nature of the work to be performed: will the data be manipulated, measured, or built upon in software?
DTM Data and Topographic Requirements
A Digital Terrain Model must be used when decisions for the development project rely on knowledge of the site’s exact 3-D form. DTM data is not a standard plan but is required for drainage design, flood risk assessment, cut-and-fill calculations, environmental impact assessment, and the design of roads and infrastructure on sloping ground. Elevation data from a DTM is not found in a standard CAD map or OS plan and cannot be used to make decisions from contour lines on a printed map that are accurate enough for serious technical work.
Ordnance Survey Data and Its Specific Authority
OS mapping continues to have a distinct place in planning and property use in the UK because of the consistency, accuracy and legal status of OS data in these contexts. When mapping is required by a planning authority, a solicitor or a boundary dispute from an authoritative source, OS mapping is the benchmark for all other mapping types. This means that if OS data is requested only, not just preferred, then alternative mapping types are not submitted.
Matching the Map to the Moment
The art of map selection is knowing what kind of map is needed for a particular project and having it ready before it becomes an issue. OS mapping may be necessary for early site assessment to understand the context. CAD data is needed for technical design. DTM is required for environmental study. A compliant location plan is required for the planning submission. There is a clear requirement for mapping at each stage, and meeting this requirement with the right product is just part of being a competent project manager from start to finish.