Demonstration on open data

GIS atlas of a sewer network to the RAEPA data standard

A sewer network published as open data, restructured to the French RAEPA data standard, checked pipe by pipe and laid out as an atlas sheet.

By Ibrahima Sory Diallo, GIS specialist · built in October 2026

This is not a client assignment: I built it on public data to show engineering and environmental consultancies how I work as a subcontractor.

Context: Demonstration built on open data, not commissioned by a client.
Data: Sewer network of the Lake Annecy joint authority (SILA), data.gouv.fr, ODbL licence, version of 2 March 2026; IGN BD TOPO® and Admin Express (Licence Ouverte 2.0)
Scope: Municipality of Doussard (Haute-Savoie, France): 1,458 pipes (42.6 km) and 1,446 structures. Connections are computed on the whole network of the authority (48,711 pipes).
Tools: QGIS 3.44, Python (PyQGIS), GeoPackage

The consultancy's problem

An engineering firm taking over a network plan inherits data entered by many hands over many years: reversed flow directions, manholes without invert levels, missing connections.

Before drawing the atlas, you need to know what the data is worth, and be able to tell the client, with figures.

What the demonstration shows

Structure. Pipes and structures restructured to the RAEPA v1.1 standard (COVADIS) with its code lists, in a GeoPackage.
Check. Six repeatable topology checks: orphan pipe, dangling end, inconsistent flow direction, duplicates, missing attributes.
Lay out. An A3 atlas sheet with its index grid, and the data dictionary on a second page.

Results

A3 atlas sheet of the Doussard sewer network: pipes by type, manholes and pumping stations, topology anomalies flagged — Sheet of the demonstration (A3, reduced). In French. Open the image full size

57pipes with an inconsistent flow direction in the municipality

Inconsistent flow direction57upstream invert lower than downstream by more than 5 cm
Dangling ends5real end of network or missing connection, to be checked
Missing attributes244mostly manholes without an invert level
Duplicates and orphans0none in the municipality

The flow direction could be computed on 1,035 pipes. An inconsistent direction does not say where the error is: pipe digitised backwards, wrong manhole level or a real reverse slope. Only an as-built plan or a site visit can tell; the anomaly layer lets you work through the cases one by one.

What I deliver

PDFA3 atlas sheet and data dictionary (2 pages)
GPKGRAEPA-structured network, anomaly layer and atlas grid (ODbL, like the source)
CSVCheck report, one row per anomaly, with its coordinates

Limits

The check covers the data as published: it replaces neither an as-built plan nor an inspection. No sewer network is published as open data in Bourgogne-Franche-Comté, so the demonstration uses the most complete dataset found, the SILA one.

GIS back-up for your consultancy

I work as a subcontractor: data structuring and quality checks, maps and atlases, in your house style and under your name if you wish. QGIS, GeoPackage and PDF deliverables.

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