Geospatial information shall be managed with the same evidential, temporal, version and assurance controls as non-spatial land referencing information.

Spatial representation shall be fit for the intended use. A visually precise geometry shall not be used to imply legal or positional certainty unsupported by the source.

The project instruction shall include a spatial data specification that identifies:

spatial object classes;

geometry type and dimensionality;

approved CRS and vertical datum, where relevant;

units;

source hierarchy;

required positional accuracy and spatial resolution;

capture and interpretation rules;

topology rules and tolerances;

attribute schema and code lists;

metadata requirements;

versioning and exchange requirements;

quality checks and acceptance criteria; and

portrayal requirements for controlled outputs.

The specification shall identify requirements that differ by object class or intended output.

Each spatial dataset and geometry exchange shall identify its CRS by an authoritative name and identifier.

The CRS shall be defined in accordance with ISO 19111.

Where data is transformed:

source and target CRS shall be recorded;

transformation method and parameters shall be identified;

transformation date and software or service shall be recorded;

expected transformation accuracy shall be assessed; and

the transformed data shall be checked against known control or contextual information.

Data with an unknown or assumed CRS shall not be combined with controlled spatial information without a recorded assessment and approval.

JURISDICTIONAL NOTE (informative)
OSGB36 British National Grid is the national mapping CRS used by Ordnance Survey in Great Britain. Mapping and registration sources on the island of Ireland can use Irish Grid or Irish Transverse Mercator; current Tailte Eireann registration maps use ITM. The applicable CRS, transformation and vertical datum are to be stated in the project spatial data specification rather than inferred from the jurisdiction alone.

The mapping or imagery used as spatial context shall be identified by product, supplier, version or publication date, coverage, scale or resolution, CRS and licence.

Where geometries are captured relative to a contextual dataset, the dependency shall be recorded. A later change to the contextual dataset shall trigger an assessment of affected geometries.

Different organisations contributing spatial information to the same controlled dataset shall use compatible contextual mapping and CRS or shall provide a documented transformation and reconciliation process.

For each geometry, the organisation shall retain lineage sufficient to determine:

source or sources;

source date and scale, resolution or accuracy;

feature or document part interpreted;

capture or derivation method;

operator or process;

date created;

manual adjustments;

transformations;

quality checks; and

version history.

Where different parts of one geometry rely on different evidence, the lineage shall distinguish the relevant parts where material.

The organisation shall classify each captured geometry as one or more of:

directly supplied authoritative geometry;

traced or digitised from a plan or map;

surveyed or observed;

derived by spatial operation;

inferred from related evidence; or

indicative or representative.

Interpretation shall take account of the source’s purpose, date, scale, resolution, symbology, stated limitations and relationship to current physical features.

A source geometry shall not be altered to remove a conflict solely for visual neatness. Adjustments shall be recorded and the source representation preserved or recoverable.

A spatial index, cadastral polygon or other search geometry shall not be treated as a substitute for the authoritative title, folio, title sheet, registry map, deed or filed plan where the latter is required for the intended use.

Where an index geometry and the authoritative document differ, the organisation shall:

retain both representations;

record the discrepancy;

assess the source limitations;

determine the representation approved for the intended purpose; and

record the decision and approver.

The organisation shall not purport to resolve the legal extent beyond its competence or authority.

Where a right is unregistered or its extent is not authoritatively mapped, the geometry shall be based on the best available combination of documentary, physical, inquiry and contextual evidence.

The geometry shall state:

asserted basis;

evidence;

interpretation;

quality status;

uncertainty; and

matters requiring confirmation.

An inferred extent shall be distinguishable from an authoritative or verified extent in data and outputs.

Topology rules shall be defined by object class and purpose.

The organisation shall check, as applicable:

geometry validity;

self-intersection;

unintended gaps or overlaps;

duplicate geometries;

slivers;

containment within the relevant requirement boundary;

continuity across dataset tiles or delivery boundaries;

adjacency consistency;

vertical-stratum consistency; and

correspondence between geometry and attributes.

A fixed tolerance shall not be applied without considering source accuracy, map scale or resolution, intended use and consequence of error.

Where a continuous coverage model is required, every gap and overlap above the approved tolerance shall be resolved or recorded as an accepted finding. The original source geometries shall remain traceable.

An intersection used to determine affected land or rights shall consider:

horizontal extent;

vertical extent;

temporal validity;

object status; and

the purpose and rule of intersection.

Objects that overlap horizontally but do not overlap vertically or temporally shall not be treated as affected unless the applicable requirement provides otherwise.

Derived spatial information shall be reproducible.

For each derivation, the organisation shall record:

source datasets and versions;

operation or rule;

parameters and tolerances;

date and process;

output dataset and version;

exceptions or manual edits;

validation results; and

affected outputs.

Spatial dataset metadata shall conform to ISO 19115-1 and shall include, as applicable:

title and abstract;

responsible organisation;

purpose;

geographic and temporal extent;

CRS;

lineage;

creation and revision dates;

update frequency or trigger;

quality information;

access, security, licence and use constraints;

distribution format; and

contact point.

A geospatial delivery shall include:

dataset and version identifier;

schema or feature catalogue;

CRS and units;

geometry type and dimensionality;

attribute definitions and code lists;

metadata;

quality report;

known issues;

delivery manifest or checksum where appropriate; and

relationship to the project instruction and relevant outputs.

The receiving organisation shall check that the delivery can be interpreted without relying on undocumented local knowledge.

The portrayal of spatial information shall preserve the meaning and status of the underlying objects.

A controlled land plan shall, as applicable, show:

title and purpose;

plan, sheet and version identifiers;

issue status and date;

geographic coverage;

north indication;

scale or statement that the plan is not to scale;

scale bar where meaningful;

legend;

requirement boundary;

relevant land or derived parcel identifiers;

distinction between requirement classes or right classes;

base mapping attribution and date;

CRS or grid information where required;

continuation and match-line information;

inset or location information;

copyright, licence and use limitations; and

approval status.

Line width, offset, colour, shading, hatching and labelling shall be selected so that the intended boundary and object remain unambiguous at the intended output size and in any required monochrome or accessible form.

Map scale shall be selected by reference to legibility, source accuracy, extent and procedural requirements. This document does not prescribe a universal scale.