accurate gps tracker app for survey work

[mtbdudex]

Hi - I am in need of an pretty accurate gps tracker app for survey work, I will be using my new iPhone 7 Plus.
I realize this is NOT accurate enough for legal work, but within 2 feet is what I hope for.

I’m the “executor” of the private road Kendra LN Road Maintenance Agreement (RMA), on behalf of the 16 residents of Kendra LN. I just overtook this position this Summer-2016.

Our private dirt/gravel road Kendra LN is in desperate shape , simply it’s in poor condition, appears to never have been designed/built “right”.

I have the 1988 original road survey and centerline locations, but seems the actual road is 14-16 feet off centerline.

Before we proceed with any serious road re-work, I'd like to have good idea of the road centerlines.

 

[aaronvan]

Unless the app deliberately "fuzzes" the location, aren't they all the same? It's the iPhone itself providing the GPS coordinates.

 

[sparksd]

2 feet? Note that the US Govt claims 7.8 meters at 95% confidence level and you should certainly see at least this with the phone's A-GPS (Assisted-GPS which uses both GPS and cellular network assistance). But don't count on 2 feet - you need high-grade surveying gear for that.

 

[mtbdudex]

appreciate replies, so no matter the app on the iPhone I'm limited to the accuracy??

I've got this app called "Bike Brain", I use it to map my MTB routes.
Yesterday afternoon I walked very slowly down the centerline of our road, when I mapped it went all over the place.
My starting point was center of the T intersection on bottom, and ended up at the top curve stake intersection point.

The plot line makes me look like I'm caddy-wampus walking!
(these were done with my iPhone5s, as my iPh7 is not here yet)

 

[sparksd]

Yes, you're seeing the results of the accuracy limitations. You should have seen what your track would have looked like before Selective Availability was turned off (SA was the introduction of random, time-varying errors of up to 100 meters in the civilian signal and was turned off by Pres. Clinton's order in 1996). What we have now is orders of magnitude better but it still has its limits.