North?

B

Bruce Dawson

Active Member
So I have a line that I need to stake with a deed call of "North 500 feet" and also "West 2000 feet". My first inclination is to stake it at True North. I am working in Washington State Plane North (NAD 83). I see that under Cogo,Cogo Tools, Factors I can get the convergence angle from Grid at the start of the line, a found monument.

So would it be good practice to use the convergence angle at that monument to determine the direction for this "North" line, then just deflect 90 degrees from it for the "West" line?

Thanks,

Bruce
 
Sdrake14

Sdrake14

Active Member
Shawn Billings said:
In Cogo, Basic, Direct change bearing to Geo (geodetic). Then enter the geodetic azimuth or bearing. No need to keep up with convergence. J-Field does it for you.
Click to expand...
Hi Shawn,
So I found a variance between the Geodetic north in jfield and a geodetic line split in Carlson survey. Now I am splitting hairs here, and in the real world the difference is meaningless, but still curious and know you use Carlson also.

So I am resetting a Section corner on a Township line between the nearest 2 quarter corners, the variance is between a Carlson geodetic split and taking a direct setout in Jfield and using the geodetic bearing inverse to set between the found points.

The Jfield result matches a strait grid midpoint between the two in Carlson but the Carlson geodetic split is about 0.09' south. I'm thinking this right and Jfield not correct. (unless expecting the wrong result here, I get that I don't care...like if I found this I'd be like "pthait" (minion style) and move on) But I am curious.

Any thoughts? thanks
 
Shawn Billings

Shawn Billings

Shawn Billings
5PLS
I've got two points from a Survey I did yesterday that are 2024 feet apart.

Carlson can annotate the Mean Geodetic Bearing, but from what I see, not the forward or reverse geodetic bearing.
The Mean Geodetic Bearing from Carlson on this line is S 75°36'32.76" E

From J-Field the Forward Geodetic Bearing is S 75°36'39.04" E
From J-Field the Reverse Geodetic Bearing is N 75°36'26.60" W

The average of the Forward and Reverse Bearing from J-Field is S 75°36'32.82" E, a difference from Carlson of only 0.06".

I'm may not be following all of what you are saying in your scenario, but it's important to remember that the Geodetic Bearing from A to B will not be the same as the Geodetic Bearing from B to A, unless they are both on the same meridian (due North and South of one another).
 
Sdrake14

Sdrake14

Active Member
I understand this. What I am seeing is my single proportion on the town line should follow a geodetic (rhumb) and it appears Carlson's split is this while the Jfield is keeping me on a grid line between the two, even though I use the "geodetic" in the direct calculation...

I think..
 
Shawn Billings

Shawn Billings

Shawn Billings
5PLS
I just created a point at the end of my 2024' line using the same forward geodetic bearing that was reported from inverse in J-Field and it hit the exact same point. I have to admit, I am not a PLSS surveyor so I am not the best person to advise on PLSS reconstruction.
 
Vladimir Prasolov

Vladimir Prasolov

Well-Known Member
JAVAD GNSS
Bruce Dawson said:
So I have a line that I need to stake with a deed call of "North 500 feet" and also "West 2000 feet". My first inclination is to stake it at True North. I am working in Washington State Plane North (NAD 83). I see that under Cogo,Cogo Tools, Factors I can get the convergence angle from Grid at the start of the line, a found monument.

So would it be good practice to use the convergence angle at that monument to determine the direction for this "North" line, then just deflect 90 degrees from it for the "West" line?

Thanks,

Bruce
Click to expand...
Hi Bruce,
Could you send me coordinates of the points (origin, north and west) please. I will verify our algorithm.
 
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