Spatial data is the fuel for 3D Applications, but all too often the fuel supplied is inappropriate. The software applied and expertise required when modelling a flood event or predicting a cityscape’s lineof-site is exactly the same using highly precise data as it is for generalised data. The difference is in how well that analysis relates to the real world … i.e. whether the analysis is correct or not. Conversely, supplying highly accurate or dense data to a generalised analysis can cost both time and money which is not reflected in the final product. Hence the word of this paper is: appropriate. Apply the most appropriate data to your application. There is nothing wrong with “approximate” or “inexpensive” 3D data, as long as it is appropriate for the level of analysis being performed.