Amogh N P
✦ In loving memory of Amogh N P — Architect · Designer · Visionary ✦
A laptop on a desk showing a GIS map of a historic city with coloured heritage layers overlaid on an old map, beside a printed conservation-zone plan, no people, no readable text.
Unit IIIAdvanced Practice & Technique in Conservation

Geospatial Data & GIS for Heritage

Layers, historic maps and spatial analysis.

≈ 45 min + studio task

A historic city is too big to draw and too rich to list — it needs a map that thinks. Learn GIS fundamentals — vector (points, lines, polygons + attributes) versus raster (a grid of cells), layers and the attribute table; georeferencing historic maps onto modern coordinates to read change over time; spatial analysis (overlay, buffer, proximity) for listing, risk and zoning; and how GIS differs from CAD.

Learning objectives

By the end of this lesson, you will be able to — mapped to the course outcomes for Advanced Practice & Technique in Conservation:

1
CO3 · Understand

Explain GIS fundamentals — vector vs raster, layers and attributes.

2
CO3 · Apply

Georeference a historic map and overlay it on modern coordinates.

3
CO3 · Apply

Use spatial analysis for heritage listing, risk and zoning.

4
CO3 · Analyse

Distinguish GIS from CAD.

Vector, raster, layers

GIS fundamentals

A GIS holds the world as vector features (with attributes) and raster grids, stacked as layers; the attribute table makes a map queryable — and that is what separates GIS from CAD.[1]

Vector, raster & layers VECTOR — features + attributes point line polygon RASTER — a grid of cells a scanned map, an aerial photo, a surface The ATTRIBUTE TABLE — name, date, grade, condition — is what makes a map queryable. Vector and raster are not interchangeable — each suits different tasks.
DiagramGIS holds data as vector — points, lines and polygons with attributes — and raster, a grid of cells, stacked as layers

How GIS holds the world

A GIS captures, stores, analyses and DISPLAYS spatially-referenced data. It holds the world two ways. VECTOR data represents discrete features as POINTS (a monument), LINES (a city wall) and POLYGONS (a conservation-zone boundary), each carrying ATTRIBUTES in a linked table. RASTER data is a GRID OF CELLS (pixels), each with a value — a scanned historic map, an aerial photo, an elevation surface. Thematic datasets stack as LAYERS, and the ATTRIBUTE TABLE — name, date, grade, condition — is what makes a map QUERYABLE. MISCONCEPTION→correct: 'vector and raster are interchangeable' — vector suits features and analysis, raster suits imagery and continuous surfaces.[1]

GIS vs CAD GIS georeferenced (real coords) attribute + analysis-driven a queryable database 'which sites within 50 m of the river?' CAD geometry / drafting arbitrary local coordinates no spatial database draw the building precisely Draw the building in CAD; manage the precinct in GIS. They are not the same tool. GIS locates, links data and analyses; CAD drafts.
DiagramGIS is georeferenced and attribute and analysis-driven; CAD is geometry and drafting in arbitrary local coordinates
Past on present

Historic maps & analysis

Georeferencing a scanned historic map onto modern coordinates lets you overlay past on present and read change; spatial analysis turns an inventory into a management tool.[1, 2]

Georeferencing a historic map scanned historic map modern coordinates match control points → warp (rubber-sheet) Now the old map overlays the present — read lost streets, demolished structures, settlement growth. The closest thing to seeing the city as it was, measured against the city as it is.
DiagramGeoreferencing warps a scanned historic map onto modern coordinates by matching control points, so past overlays present and change is visible

Overlaying past on present

One of GIS's most powerful heritage uses is GEOREFERENCING HISTORIC MAPS: a scanned old survey is given real-world coordinates by matching CONTROL POINTS (features common to old and new), often by 'RUBBER-SHEETING' — warping the scan to fit modern coordinates. Now the historic map overlays the present, and you can read CHANGE OVER TIME — lost streets, demolished structures, the growth of a settlement — and even DIGITISE (vectorise) vanished features off the warped raster. It is the closest thing to seeing the city as it was, measured against the city as it is.[1, 2]

GIS vs CAD

At a glance

AspectDetailNote
VectorPoints, lines, polygons + attributesBoundaries, features, analysis
RasterA grid of cells (pixels)Imagery, scanned maps, surfaces
GISGeoreferenced + attribute-drivenQuery and analyse
CADGeometry / drafting, local coordsDraw, not analyse
Historic map useGeoreference (rubber-sheet)Overlay past on present
Vocabulary

Key terms

GIS

A system to capture, store, analyse and display spatially-referenced data.

Vector / raster

Discrete points/lines/polygons + attributes / a grid of cells (pixels).

Attribute table

The database linked to features — what makes a map queryable.

Georeferencing

Assigning real-world coordinates by matching control points (rubber-sheeting).

Buffer / overlay

Zones around features / combining layers — core spatial analyses.

GIS vs CAD

Georeferenced, attribute/analysis-driven vs geometry/drafting in local coordinates.

Apply it

Studio task

For a historic precinct, list the GIS LAYERS you would build (monuments as points, walls as lines, conservation zones as polygons, a scanned old map as raster) and the attributes each would carry. Then describe how you would georeference the historic map and what one spatial analysis (a buffer around a monument, say) would tell a conservation authority.

Check your understanding

Self-assessment

1. In GIS, a conservation-zone boundary would most likely be stored as a —

2. Georeferencing a historic map lets you —

3. GIS differs from CAD because GIS is —

In a nutshell

Recap

GIS holds the world as vector (points/lines/polygons + attributes) and raster (a grid of cells), stacked as layers.
The attribute table makes a map queryable; vector and raster suit different tasks and are not interchangeable.
Georeference historic maps (rubber-sheeting) to overlay past on present and read change over time.
Spatial analysis — overlay, buffer, proximity — supports heritage listing, risk mapping and conservation zoning.
GIS is georeferenced and analysis-driven; CAD is drafting in local coordinates — they are not the same tool.
The evidence

References & further reading

  1. [1]Heritage GIS guidance (Historic England GIS for heritage; ESRI cultural-resource GIS) — vector/raster, analysis, GIS vs CAD.
  2. [2]Geospatial Historian / Harvard Library tutorials — georeferencing and vectorising historic maps.
  3. [3]Krygier & Wood, Making Maps: A Visual Guide to Map Design for GIS — geo-visualisation and cartography.
  4. [4]Eun Sul Lee & Forthofer; O'Sullivan & Unwin, Geographic Information Analysis — spatial analysis methods.

Further reading

  • Krygier & Wood — Making Maps.
  • O'Sullivan & Unwin — Geographic Information Analysis.
  • MacDonald (ed.) — Digital Heritage: Applying Digital Imaging to Cultural Heritage.

Sources gathered and fact-checked June 2026. Published values vary by source, sample and method — treat as indicative and confirm against the cited standard before structural use.