Yep. Does Google earth, labins, terraserver, etc. give you coordinates on a 3 dimensional grid format? Some of the things I was thinking do require exact coordinates. But nevermind..just drink your coffee... 
Nothing to see here, just move along....certainly no violation of privacy in any way... 
3d GRID as opposed to a regular latitude and longitude?
I assure you that given the advancement of photogrammetry and satellite recon, there is no need to GPS your house in order to get an accurate fix on it. If they have an aerial picture of it, than they have it. Close enough to drop one down the sewer vent if need be.
Saying that they needed to GPS to get the accurate 3D location of your house as opposed to interpolating it off of all the elevations they have from regular USGS quad sheets is ridiculous. GPS locations for the "3rd dimension", elevation, are notoriously the most errant. Whereas, a high res scaled photograph can be fixed and used to identify improvements horizontally to within a foot. And contours derived from any number of flood studies and other aerial surveys are good to within 2' on an identifiable hard surface.
Certainly, +/- 2 foot meets the criteria of "exact coordinates", that they can achieve in the office without raising the suspicion of having that faux census taker come to your house?
In order to get sub centimeter accuracy, they will need to set up survey grade GPS, which requires a
stationary observation of a few minutes, or a real time kinetic occupation, which requires another
stationary GPS survey base unit to be active nearby. But that only gives the coordinates of where the unit was set up, not the front door.
Or, perhaps, they can get a surveyor out there to get some exact coordinates on your front door?
Now given the inaccuracy of a handheld GPS unit - commerical or military, compared to some desk jockey pixelating your house to +/- 12" horizontally, and 2 feet vertically, I suspect that there is another reason for the GPS location.
Most likely if this is a work program, they want to ensure that the worker actually went to the house! The worker can't say "I got all this data from these houses" and then provide a location that comes back to the driveway down the street, or worse yet, "Joe's bar and grill"p.s. I used the term "front door" as an example. Feel free to replace the term "mushroom patch" if needed.
By the way, it is an invasion of privacy. My gates are locked. The driveway is a half mile long. I told the Census to shove their American Community survey. IIRC, they are entitled via the Constitution to conduct a census every ten years to know the number of people, the number working, and the number of rooms in a house.
That's all the orange juice they get.
