GPS smart phone app

Tammy found a GPS app for her smart phone.  It is called: Backcountry Navigator.  I tested it out by walking around much of the ranch's boundary.  I then downloaded the data to Google maps.  My mapped route is pretty close to Google's (via the USDA Farm Service agency's) satellite image for the ranch but not perfect. East/west and north/south are off a few feet with east/west off by a greater amount.

The mapped route had me walking through part of the barn when in reality I walked just south of it.  The route did have me start and end correctly in the house even though my entry and exit into the house were through the same door, which is in the NW corner of the house.  Therefore the line from the right going into the house is wrong as I have no door in the NE section of the house.

 
And the GPS app had me some distance off the fence line when I actually walked right next to the fence.  In the photo below I had walked to the corner even if the track does not have me doing that.  Also I walked in a straight line to under the tree where I marked an X.  I wonder if walking under the tree threw the GPS app off and it then guessed that I had walked north of the tree?

Also when I walked along the river I often was shown to have been walking in the river.   In the photo below I walked to the right of A, the end of land.  Then I backtracked to go to B as I had to walk around the tree that is in the 7 o'clock position from B.  I then walked a little to the left of B then up to C.   As you can see this doesn't not match the route mapped.  The route here is in the middle of the river and I assure you I did not walk in the water especially as this is December and the water is very cold.

I've noticed the same problem with my property boundaries/fence lines with other government agencies who have mapped the ranch using satellite photos.  I think the original GPS coordinates for the USDA Farm Service Agency satellite photos were inputted a little off, or is this in the margin of error for GPS units?

The distance I walked seemed to be correct.  However the elevation gain and loss were way off.  The GPS app had me gaining 679 feet in elevation and losing 820 ft.  I walked in a circle starting and ending in my house.  The elevation gain and loss should be identical.  Also I think the elevation numbers are off by a more than a factor of 10.  My estimate of the elevation gain/loss to have been 20 to 30 ft.

Still, for a $9.99 app, this may be a good deal as a decent GPS unit - or at least the one I would like - is $600.