Purpose of the paper

This paper is intended to explain how to use official sources to complete and/or correct OpenStreetMap data.

Introduction

In Belgium, administrative boundaries as legally defined are fixed and can only be changed by law, ordinance or decree. The General Administration of Property Documentation is designated by the federal authorities as the authentic source of Belgian administrative boundaries. ⁽¹⁾

The data are freely available on the web site of the SPF Finances / FOD Financiën / FÖD Finanzen. In addition, it should be noted that these data are more accurate than those from NGI.

A lot of administrative boundaries are already present in the OpenStreetMap database.

At the municipality level, it appears that the OSM alignments of boundaries differ slightly from the alignments published by the SPF Finances / FOD Financiën / FÖD Finanzen.

In addition, at the lower level, i.e. at the division level, boundaries are partly absent. A division is a part of a municipality.

Why do we need the division level?

The division boundaries, i.e. level 9 in Belgium, are interesting for several reasons.

Firstly, this administrative level is still used on current cadastral documents.

Secondly, the divisions are historically the successors of the pre-1977 municipalities. While their alignments are not always similar, they are generally identical. Sometimes the place names are different. ⁽²⁾ This information, i.e. the boundaries and names, is useful for historians, genealogists and all those who read old documents. Thirdly, the postcode boundaries are essentially based on the level 8 and level 9 administrative boundaries.

Existing data

It is interesting to note that the terminology used may differ from one service (e.g. NGI) to another (e.g. Finances) are different. The following table shows the different sources and terminologies for administrative boundaries.

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