In a virtual reality or mixed reality environment, an HMD device is configured to use surface reconstruction data points obtained with a sensor package to identify a location of a floor of a real world environment in which the device operates by sorting the data points by height into respective buckets where each bucket holds a different range of heights. A bucket having the greatest number of data points that are below the height of a user of the HMD device is used to identify the height of the real world floor, for example, by calculating an average of height values of data points in that bucket. A floor for the virtual reality environment may then be aligned to the identified height of the real world floor.