Base mode - antenna height

[rsurveyor1 (Surveyor)]

Hello y’all

I’m working on a surveying project right now, and I’m having a little bit of trouble regarding the Antenna height.

I’m using the base+rover setup, rtk mode, I have a stretch of 1.3 km to survey, approximately 600 points to collect, and will do the job in 2 days (300 points per day).

On day 1, I’ll place the base at the top of a hill near the stretch (using a tripod, a leveling base and an extension), something like this:

Since I didn’t position my base over a known control point, I’ll be using the Average Single option (Base mode -> Base Coordinates -> Coordinates Input Mode). I only made a small “X” on the ground, so I can return on day 2 and position the base on the exact same spot. This whole setup measures 1.925 m from the ground to the L1 phase.

I could position the base on a known control point, but I’ll be leaving the base unattended, and out of my sight – something I don’t wanna do. I’ll collect all the data I need, and then will collect the known control point (at the end of day 2), and make the necessary adjustments.

Using the Average Single on base mode, I had the following results:
Lat: 29,143…
Long: 57,17…
Height: 732,414 m

After setting up the base, I proceed with the surveying, and collect 300 points. And that’s the end of day 1.

On day 2, I’ll position the base at the exact same spot that was on day 1, since I’ve made a small mark on the ground to locate it. But instead of using the Average Single on base mode, I’ll use the Manual Coordinates, that I’ve collected on Day 1 (Lat: 29,143… Long: 57,17… Height: 732,414 m)

The problem is, when you use the Average Single, there’s no field to input the Antenna Height – it only appears using the Manual Input Mode.

Input mode: average single. No antenna height input.

Input mode: manual. Antenna height available.

So, on day 2, which value should I put on the Antenna Height? Should I consider the 1.925 m from my initial setup, on day 1? Should I mark it zero dudes?

Help me out with my train of thought here, I’m kind of lost.

Cheers.

[timd1971]

Hopefully someone of intelligence will help you out soon.

[bide]

The theory is this:

If you put your base at a random location and let it “average” a coordinate, then that coordinate is at a point in space exactly where the base antenna is.

It does not matter if you do average single, or have access to an NTRIP caster and do average fix to get your base location. It does not matter if your base is on the ground or on a pillar or on a tripod or pole. All that matters is where the antenna is. The data you have is ANTENNA HEIGHT

NOW: Say you want to continue the survey and bring your base back on a different day. Ideally, one would use the process of ‘localization’ like @michaelL mentions frequently, but with the current tool set, the correct way to do this is exactly what you mentioned: Make a mark on the ground.

If you want the coordinate of that mark on the ground, then you are going to have to either:

A) Start a survey project for your base; set parameters that will work for your situation (like average single; etc.); enter your antenna height; collect 1 point. After point collection is finished, view the list of points and see the adjusted height of your mark.

B) Copy the averaged antenna coordinates and the antenna height into your notes and subtract the height of antenna (a.k.a. phase center) above the mark.

Now the data you have is MARK HEIGHT

Here comes day 2. You can enter your MARK HEIGHT into the manual base coordinates. You have a new tripod setup over the mark, so you can enter the new height of antenna over the mark into the “Antenna height” field.

Does that help?

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p.s. if you can visit that “known control point” at the start and end of each day, you will have several point collections of a common point that you can compare and gain a measure of confidence from and perhaps be able to extend that confidence to the points measured in between those times.

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p.p.s. we could call option "A" the millenial method where the calculation and the evidence of it is stored in the survey project; and we could call option "B" the old-school method where the information and calculation is written in your notebook.

[timd1971]

@timd1971

Hopefully someone of intelligence will help you out soon.

Looks like you hit the JACKPOT!

[timd1971]

Hopefully this helps too?

Collecting & Staking / Setting Out Points (BASE AVERAGE SINGLE)(Multiple days)

(2) Reach RS (Edison chips) (1) as the BASE (1) as the ROVER LoRa communication between them. Just to make sure everything is ok here, got a question to help clarify things. Set my BASE up anywhere in the area of work with best clear sky view and highest elevation. I let it AVERAGE SINGLE for a few minutes. (not using NTRIP CORS) (I mark where the BASE is physically for day 2 work)(note: In my case I do NOT need to use a KNOWN POINT from public or surveyor provided records etc to set on.…

Per @igor.vereninov this is the key:

Finding Accurate Base Position

If you are averaging base position your antenna height is zero. Non-zero antenna height should be used if base is set up on a known point. Antenna height is elevation from known point (which is usually on the ground) to antenna level (antenna is usually on a tripod). In your case you are directly measuring the location of your antenna using GPS, so base antenna height is zero.