La Rochelle, France knew during the second half of the twentieth century an important increase of its permanent and seasonal population. Since 1999, the city is grouped together with 17 others municipalities (communes) into an intercommunality (cooperation group between communes) : La Rochelle’s community of Agglomeration (CDA-LR). Because of an attractive coastal position, the CDA-LR is subjected to a strong growing of population. It showed itself by a massive urban spread. This urban spread is today particularly visible in the peripheral municipalities of the CDA-LR. These municipalities absorb the inhabitants because they cannot find a housing in the city of La Rochelle. The CDA-LR is under a strong land pressure because of its attractive coastal position. .Inhabitants are thrown back towards the peripheral by the price of the housing. The mastery of the urban spreading of the CDA-LR is one of stakes of the future land development plan (schema de coherence territorial : SCOT). The SCOT is at present in progress. This paper present a method to analyse the urban spread. The aim is to model the urban spread phenomenon between 1950 to today. Cadastral dataset is used as an input. This modeling is made with space and time analysis tools implemented in a geographical information system. Theses tools are described in the first part. They also present two indexes to analyse the urban spread. In a second part, theses indexes are compared to planning documents in order to verify the coherence between urban planning strategies and the concrete presence of buildings on the field.