Where are you getting your height info?
I just checked again and found it to be less than 1 foot off on a random topo I pulled out of the drawer.
Here's my info.
Google Map Location
https://maps.google.com/maps?q=212th+St+SW,+Snohomish,+Washington&hl=en&ll=47.807091,-122.309968&spn=0.002183,0.003846&sll=48.02805,-121.819153&sspn=0.098385,0.26144&t=h&gl=us&geocode=FcV42QIdIZ61-A&hnear=212th+St+SW,+Snohomish,+Washington&z=19
[image: RUqu_mapheighttestmap.JPG]
Google Map Find Altitude.
[image: b59q_mapheighttest.JPG]
Here's the professional survey and topo
[image: LflH_mapheighttesttopo.JPG]
I'd say that's easily within a foot.
Let us know how you got your figures.