Because we are using different methodologies. The activity data is the same but the rationale and scope for using the data is different. Google’s EIE is showing you, for example, all of the in-bound and out-bound trips in your council area, as well as in-boundary journeys. For Snapshot, we’re seeking compliance with the GPC protocol so a proportion of the in-bound and out-bound trips need to be attributed to other councils.
For example, North Sydney Council and Mosman Council in inner Sydney share a boundary. In EIE you can see all of the in-bound and out-bound trips to and from each council. But if we included then all within Snapshot then we’d be double-counting many trips and essentially doubling the transport emissions for each council area. So we apply a methodology consistent with the standard GPC protocol to account for this and avoid double-counting of emissions.