Delineating the French Urban Areas Ongoing Thoughts

Delineating the French urban areas Ongoing thoughts

Vincent Loonis, Vianney Costemalle

Geographical repositories and methods division French national institute of statistics and economic studies (Insee)

EFGS, Manchester, 11th October 2019

Vincent Loonis, Vianney Costemalle Delineating the French urban areas Introduction

France has delineated its urban areas at a regular pace for the past 200 years. The current definition has remained unchanged since 1962. For the next delineation, to be published in 2020, Insee has to face new challenges. Easy-to-access geospatial information leads to: scholars and official bodies questioning Insee’s implementation of the definition. increasing the number of urban area definitions (based o, population densities or built-up areas). A solution may consist in studying the robustness of the various definitions, while finding a way to combine them.

Vincent Loonis, Vianney Costemalle Delineating the French urban areas Introduction

Territorial classifications are classifications. As such, they are subject to statistical conventions. Some of these conventions are: classical: thresholds on population, on density rates... specific to spatial information: distance, reference system, choice of geographical layers, quality of the latter. The question raised by Insee is how to measure the influence of geographical conventions on territorial classifications. We will illustrate our ongoing thoughts with two examples: a density-based definition a built-up-area-based definition

Vincent Loonis, Vianney Costemalle Delineating the French urban areas density-based deﬁnition

Figure: Urban center: a cluster of contiguous 1 km2 grid cells (excluding diagonals) with a population of at least 1 500 inhabitants and a minimum global population of 50 000 inhabitants after gap-ﬁlling.

(b) Urban center in Caen: 125 000 inhabitants and 3 municipalities (a) The LAEA grid

Vincent Loonis, Vianney Costemalle Delineating the French urban areas density-based deﬁnition

(b) leads to another delineation of (a) Another grid, with the same Caen’s urban centre, i.e. 156 000 properties as the former, inhabitants and 10 municipalities. constructed by rotation and translation,

Vincent Loonis, Vianney Costemalle Delineating the French urban areas density-based deﬁnition

Depending on the rotation or the translation of the grid: 17.5 million of inhabitants 431 municipalities are are always in an urban always in a so-called city centre 545 municipalities are 8.3 million are sometimes sometimes in and in and sometimes out sometimes out An average of 22.5 million An average of 684 inhabitants are classiﬁed as municipalities are classiﬁed living in an urban centre. as City. The results are robust at the national level but may be more unstable at the local level. How to manage the sensitivity while preserving the spirit of the method ?

Vincent Loonis, Vianney Costemalle Delineating the French urban areas density-based deﬁnition: managing the sensitivity

Consider the dwellings living in all the urban centres deﬁned by the various rotations or translations of the oﬃcial LAEA grid.

Vincent Loonis, Vianney Costemalle Delineating the French urban areas density-based deﬁnition: managing the sensitivity

Gather them by a 200-meter rule, you will get a delineation that is robust to the underlying choice of the grid and that ﬁts with the French built-area-based deﬁnition.

Vincent Loonis, Vianney Costemalle Delineating the French urban areas Built-up area based typologies

1 Urban units (Insee) 2 Localities (European regulation for census) 3 Sustainable development goals (UN HABITAT, indicator 11.7.1)

Vincent Loonis, Vianney Costemalle Delineating the French urban areas Urban units in France

1) continuity of build-up areas (200m between buildings)

Vincent Loonis, Vianney Costemalle Delineating the French urban areas Urban units in France

1) continuity of build-up areas (200m between buildings)

Vincent Loonis, Vianney Costemalle Delineating the French urban areas Urban units in France

2) urban area : at least 2000 inhabitants

Vincent Loonis, Vianney Costemalle Delineating the French urban areas Urban units in France

3) classiﬁcation on administrative units : at least 50% of population within a continuous urban area

Vincent Loonis, Vianney Costemalle Delineating the French urban areas Sensitivity

Classiﬁcations reduce world complexity. Some units are at the edge between two classes. these can leads to debates and disagreements We try to detect the sensitive cases of urban units classiﬁcation in relation to the distance threshold.