Hi Everyone,
I am looking into developing a GPS/GNSS RTK system to help me fence a 10 acre property. I know where one of the survey markers is and know the longitude and latitude for it. The property has a dense tree canopy. The base/survey is clear. Has someone developed a system that would assist me to walk and mark the property lines? or would it be easier to used some of the enclosed SparkFun devices for the job? Thanks for any help in the matter. V/R PBracho
Generally you’ll either use a base + rover setup, or a module that uses PPP (timed satellite signals) that behave as the base
What kind of accuracy do you need? It’ll basically come down to whether ~1.5cm accuracy suffices or if you require sub-cm (please note those figures are based on when RTK fix is available…dead reckoning accuracy will depend heavily on mode and time since last fix)
The PNT devices with “-T”, “IM19” or all have built-in IMUs for angle/tilt compensation; the “Dead Reckoning” have methods for pedestrian/walking use where canopy cover might otherwise be an issue but are limited by the time since their last fix
Do you happen to have line-of-sight to the survey marker from the areas you need to measure?
1.5 cm accuracy is fine. The challenge here is the tree canopy. The base and rover need to have radio connectivity for the corrections.
Can you explain how the IMU will work? Would it real time integrate for position?
There is not a clean line-of-sight to all markers or property lines.
Gotcha - is there cellular service on the property?
Depending on where the original marker is, 10 acres might be within range of wifi/espnow/bluetooth, if the landscape permits :-/
Are there any areas without tree cover where you could have a clear view-of-sky?
Unfortunately no, nothing that I’ve seen that would be considered reasonably priced. Pure Inertial navigation (under dense canopy) is extremely challenging, expensive, and still not very accurate. Inertial navigation is used to bridge short gaps in the GNSS signal.
Dense tree canopy is subjective, but don’t expect much with IMU Assisted GNSS if the receiver cant lock the signals.
There is cellular service there. There are couple of area without cover. One of them is where the survey marker is. Could the rover get correction data via LoRa serial radios?
‘Could the rover get correction data via LoRa serial radios?’ - They can with a largely unobstructed line-of-sight… but with trees/dirt/earthly things in the way the signal quality degrades rapidly :-/
The major hurdle here will be determining if you’ll have enough relevant spots to survey that do have a clear view of the sky
I would like to put together a base and rover with radios to try how it works. The software that I will used will be SW for an iphone. What components will I need to do that?
In that case, I recommend you forgo a base. Use a correction service. It’s $15/month and will save you a tremendous amount of fiddling.
As @rftop points out, our devices only give you the location of the 'hamburger on a pole ’ with great accuracy. You’ll need to find a GIS app that, given a series of pre-determined/pre-loaded points (your fence posts) visually guides the user from where to unit is reporting the current location, to where the unit needs to be located to hit the point.
We’ve had a lot of users ask for this. Has anyone found a good DIY solution?
There are a lot of options available.
Here’s a sample list, ordered by cost:
[Edit] Ah, @sparky beat me to it 
That seems like a less complicated approach with less hardware. I like the approach. Can I use something like the SparkFun RTK Facet to accomplish the task?
Yes, the RTK Facet will work great. The Facet is the older generation, not waterproof, but is cheap and field proven many times over. I know we are backordered at the moment, but I believe units should start shipping in May.
Sparky,
What is the new generation for the Cacet?
v/r
P Bracho
I don’t think the imu is needed for your task. Level the rod. I would use a postcard but I would tweak the setting to drop false fixes easier. Honestly for staking long line I usually just use a total station not gps. Might use gps to establish start and end of line.