In this manuscript some theoretical background and interrelations of Geoinformatics shall be assembled. Also the most important formulae of Mathematics, Surveying, Geodesy and Cartography will be presented in short. Besides these provinces of course Informatics builds a very important part of Geographic Information Systems. In a closing chapter all basic knowledge will be combined to a short overview over Geoinformatics, where especially modelling, extensions, specializations and analysis of Geoinformatics are shown. The open source GIS application MensorGIS, written by the author, implements the described topics in source code and functionality. A final chapter refers to this program, showing where the basic principles can be found. In addition Adjustment Computation, a matter relevant in all parts of Surveying and Geodesy, is presented including samples. A Geoinformatics - from Theory to the Application 1 Introduction 2 Overview over the Basic Knowledge of Geoinformatics 3 Basics of Mathematics 4 Basic Calculations of Surveying 5 Basic Calculations of Geodesy 6 Basics of Cartography and Photogrammetry 7 Basics of Informatics 8 Geoinformatics 9 Practical Application in MensorGIS B Statistics and Adjustment Computations 1 Introduction 2 Basics of Statistics 3 Basics of Matrix Calculation 4 Adjustment Computation 5 Application of Adjustment Computation With extensive appendices and index. The Book should be read by students approaching advanced lectures with the focus on Geoinformatics. Also recommended for career changers, who want to learn more about the geodetic background of Geographic Information Systems.