Illegal building construction can be a problematic issue on densely populated metropolitan cities, especially because it leads to crooked civilization and unbalanced urban structure. The development plans define a maximum boundary for building coverage and floor ratios, but practically it is challenging to apply the plans to the real life in partly unplanned cities that are going under urban transformation, such as Istanbul. Rapidly changing settlements make it crucial to track property statuses carefully since there can be juristic consequences. In this study, we use airborne Light Detection and Ranging (LIDAR) point cloud data, stereo KOMPSAT-3 images and development plans of Guzeltepe district, locating in Uskudar/Istanbul of Turkey to detect the structures built against the development plans. The plans were converted into aGeographical Information System ( GIS) environment for the ease of analysis. Digital elevation models and digital surface models (DSMs) were created with both LIDAR and stereo KOMPSAT-3 data to obtain normalized DSMs for extracting the heights of the buildings. These heights extracted from our models were then compared with the planned boundaries. Also, the two different dataset's accuracies were analyzed. Our research may have direct implications on automatically building 3D plans and eventually instrumental for identification of illegal buildings.