In this work, a model has been developed allowing for a rapid calculation of chord length distributions (as obtained from Focused Beam Reflectance Measurements (FBRM)) as well as the prediction of measurements acquired by in-situ microscopy. The data from the FBRM and in-situ microscopy are interpreted in terms of bidimensional particle size distributions (PSD). Using the model, an algorithm was developed to monitor bidimensional growth rates from FBRM and in situ microscopy measurements. The algorithm assumes knowledge on the initial PSD, as for example in a seeded crystallization, and will provide insight in how temperature and supersaturation affect growth rates. Knowledge of multidimensional growth rates and their dependence on operating parameters is a key requirement for the control of crystal size and shape in industrial crystallization. The models and techniques developed in this work provide a better understanding of multidimensional crystal growth and can form a basis for on-line crystal shape control.