Systems and methods are disclosed to implement a delta data collection technique for collecting machine characteristics data from client machines. In embodiments, the collected data is used by a machine assessment service to maintain a virtual representation of the client machine for assessments. To initialize the collection process, the client uploads an initial copy of the data in full. Subsequently, the client determines periodic deltas between a current baseline of the data and a last reported baseline, and the deltas are uploaded as patches. The machine assessment service then applies these patches to update the virtual representation of the client machine. In embodiments, to facilitate the generation or uploading of the patches, the client may generate the baselines in a different encoding format as used by the data. For example, baselines in the new encoding format may be more easily compared and manipulated during the patch generation process.