Facet rtk and survey accuracy questions

GPS/GNSS Development Boards
1

I’m using a facet rover to gather points and establish polygons and what I’m noticing is I’m unable to get an rtk fix a lot of times and stuck in rtk float. Accuracy says 2" or so which is decent enough however the repeatability doesn’t prove reliable enough.

If I mark a point in rtk fix, walk around and come back, I may or may not be in rtk fix any longer and my point will now be off by as much as 12"

Would buying another facet and linking with a radio help to get an rtk fix 100% of the time? Being off 1" is ok but not repeating and being off 2" is not ok.

2

A device in RTK fix should be extremely repeatable, assuming the correction source never moves.

What is your source of correction data?

3

My source of correction is a fixed station on rtk2go that’s about 100 miles away.

4

You need a correction source that’s much closer for high accuracy. Like 5 or 6 miles away.

5

Based on my personal experience, I would say that up to 40 km (25 miles) a fixed solution is easily obtained by working with all 4 constellations.

Only with GPS and Glonass have I had some delay to obtain a fixed solution at that distance of 40 km.

More than 100 miles I would say that it is practically impossible to obtain a fixed rtk.

So you should look for another source of corrections closer to your position.

6

Fair enough

All thing said… How do I obtain this without a source being available?

Is this where having two units setup as base/rover comes into play?

7

Right, you need two teams. One in base mode and the other in rover.

You broadcast the corrections by radio, for example.

Or by ntrip internet if you have a cell phone signal.

8

Sounds like I’ll get another facet rover and a radio.

Another question. Is there a way to add a trigger to the pole? Having to click buttons and icons on the phone for swamps is such a pain esp in the sun and trying to get the pole level.

9

Are you asking if there’s an external mechanical button that can be attached to the RTK product? Currently the only ways to mark a spot are: press the setup button to show the ‘Mark’ menu (records a custom NMEA sentence to the log file) or within the data collector software (you mention SW Maps, so it’s hitting the mark button). There is not currently a way to add an external mechanical button but that’s an interesting idea.

10

Lots of surveyors mount their data collector (phone, tablet, etc.) to the survey pole. Hold the pole with one hand and push the button with the other. Using bipod legs for the survey pole helps too; you can level the pole and let go. Then you have both hands to collect data.

I do both - mount my tablet to the pole and use bipod legs, works well for me. Everyone figures out for themselves what works best for them. If it’s taking a while to get a fix, or I want to average a lot of epochs for an important point, I setup the pole with the bipod legs, and disconnect the tablet. I go sit in the shade with my tablet and eat my lunch.

Search “survey pole mounts” or similar.

Search “survey pole bipod” or similar.

11

sparky:
Are you asking if there’s an external mechanical button that can be attached to the RTK product? Currently the only ways to mark a spot are: press the setup button to show the ‘Mark’ menu (records a custom NMEA sentence to the log file) or within the data collector software (you mention SW Maps, so it’s hitting the mark button). There is not currently a way to add an external mechanical button but that’s an interesting idea.

Is there a description of the custom NMEA sentence someplace so I know what to look for?

Thanks!

12

l_boltzmannEMB:

sparky:
Are you asking if there’s an external mechanical button that can be attached to the RTK product? Currently the only ways to mark a spot are: press the setup button to show the ‘Mark’ menu (records a custom NMEA sentence to the log file) or within the data collector software (you mention SW Maps, so it’s hitting the mark button). There is not currently a way to add an external mechanical button but that’s an interesting idea.

Is there a description of the custom NMEA sentence someplace so I know what to look for?

Thanks!

Did anyone ever reply to this? I would like to know this info as well. There doesn’t appear to be anything in the manual… Thanks,