Did my first survey yesterday, Sunny day in a city park. I was surveying the sediment thickness in a lake. I need to measure the top of the sediment and the bottom to create volume and elevation maps. There are city skyscapers to the east a little over 1000 feet away and trees to the west, but north, south , and above mostly clear.
I had the facet L band as a temp. base and Facet as rover and connected over internal radios as i was not very far away and good line of site in all positions.
I figured the survey should take two or three hours, but ended up taking 7 hours because the facet rover would not hold its FIX, the signal would drop to DGPS and sometimes take quite a few minutes to reacquire FIX before i could take a measurement. Distance away from base did not seem to effect the time it took to reacquire FIX. And it was probably worse on the south side of the lake or closer to the base than further away. I was never more than 700 foot away from the base, and the fix seemed to return faster when i was further away.
My question is, could this be a radio issue? someone on same frequency? Would the Lora radios provide a stronger connection between base and rover? Or is dropping FIX more of a satellite reception issue? I had between 26 and 32 satellites IN USE during the entire project.
Additionally, I should be set up on Missouri’s corrections service this week. Can i get corrections from the base and the service at the same time or is it one or the other. For example the base collects correction then the rover gets corrections from both the service and the base.
Thanks,
john
It’s an either/or for which correction source is being used at any given time (in general terrestrial sources are a bit more accurate, so the Missouri ones will probably be a better default source for you long-term)
The L-band is really useful if for some reason access to a base (w/ correction data for RTK) isn’t possible in-the-field, or to save someone from needing to move their base (because it’s like a base-and-rover in one)
It may be losing fix due to movement; does the position of the unit being used as a base move at all?
To test if the Radios are the problem: switch the correction transport method to something else (wifi, bluetooth) and see if that helps you eliminate anything https://docs.sparkfun.com/SparkFun_RTK_ … transport/
The Facets are amazing devices and work very well once you get your equipment all configured and setup. I’ve done a lot of surveying with a RTK base-rover pair, and my results check very well internally (multiple surveys I’ve done over a couple years) and externally (other surveyor’s work) very well.
The internal radios in the Facets are pretty short range; my typical suggestion is to get external radios. They have better range, you can connect better antennas, and are in a different radio band. You might be having problems, as you asked about, because of other transmitters in the band (eg. WiFi).
Your issues could also be due to a lack of sky visibility. You want the base to have a very clear view of the sky, and the rover as good as you can. You could also be getting multipath in the GPS signals due to the GPS signal reflecting off the buildings.
You might need to experiment to sort out what’s going on.
I’ve had great success with two Facets (base/rover) combined with either the HolyBro radios or the RFD900x radios.
https://www.sparkfun.com/products/19032
I use a better antenna at the base and get it up high (15-20 feet).
https://www.sparkfun.com/products/15597
I tried the LoRaSerial radios last year and the results weren’t great.