GIS & Spatial Heritage

A Guide for Technical Staff and Archivists

What is it?

The GIS & Spatial Heritage plugin (ahgGISPlugin) adds geospatial search and GeoJSON export for heritage records that carry coordinates. It aggregates latitude/longitude from several sources already present in the system and exposes them through simple JSON APIs: a bounding-box search, a radius (distance) search, and a GeoJSON export suitable for loading into mapping tools.

Key features

Bounding-box search — find records within a lat/lng rectangle.
Radius search — find records within a distance (km) of a point, using a Haversine distance calculation, returning distance_km per result.
GeoJSON export — emit a FeatureCollection (application/geo+json) for records with coordinates.
Multi-source coordinate aggregation from:
- contact_information (repositories, actors)
- research_map_point (research projects)
- nmmz_archaeological_site (Zimbabwe monuments)
- dam_iptc_metadata (photo GPS)
Source auto-detection — only sources whose tables exist are queried.

How to use it

All endpoints return JSON (the GeoJSON export uses application/geo+json).

Bounding-box search

GET /gis/bbox?lat_min=&lat_max=&lng_min=&lng_max=&sources=&limit=

lat_min and lat_max are required. limit defaults to 200 (max 1000). Results are sorted north-to-south.

Radius search

GET /gis/radius?lat=&lng=&radius=&sources=&limit=

lat and lng are required; radius is in kilometres (default 50, allowed 0–20000). limit defaults to 200 (max 1000). Each result includes its distance_km from the centre point.

GeoJSON export

GET /gis/geojson?sources=contact,nmmz&limit=500

Returns a GeoJSON FeatureCollection. limit defaults to 1000 (max 5000). Omit sources to include all available sources. Each feature's geometry is a Point in [longitude, latitude] order, ready for QGIS, Leaflet, Mapbox, etc.

The sources parameter (used by all three endpoints) is a comma-separated subset of contact, research, nmmz, iptc.

Administration / setup

Run the plugin's database/install.sql. It creates no new tables — it adds a composite B-tree index on contact_information(latitude, longitude) to make range (bounding-box) queries efficient. (MySQL 8 cannot place a spatial index on float columns, so a composite index is used.)
Enable the plugin (ahgCorePlugin is required; ahgContactPlugin, ahgHeritagePlugin and ahgNMMZPlugin are optional sources).
Records only appear if they have populated latitude/longitude in one of the supported source tables.

Tips & FAQ

No results? Confirm the relevant source table exists and the records actually have coordinates; the plugin silently skips sources whose tables are absent.
Which sources are active? Only those whose tables are present are queried; pass sources= to restrict to specific ones.
Loading the export on a map? Use the GeoJSON endpoint directly as a layer URL, or save the response and import it into your GIS tool.
Radius too coarse? The query pre-filters by a lat/lng box (~111 km per degree) then refines with exact Haversine distance, so results inside the radius are accurate.

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