This book presents didactically the various models used within geomatics applications. To do so, we rely on the following statement: any model refers to an object or a system of the real world; therefore the model maker wishes to produce, during their reflection work, a model. To do so, model makers have at their disposal various approaches and formalisms. Therefore, we have to establish an overview of the approaches, formalisms and related models. The authors of this book therefore discuss: data models with specificities related to the field (spatial and temporal aspects), processing models (symbolic and digital approach) and knowledge representation models.