Hello,
Scenario:
I'm performing a mortgage survey. I need to set a traverse point so I can
observe as many front corners as possible and set a traverse point in the
backyard to continue my locations. I pick a convenient spot across the street
from my lot and set a traverse point. I find a distant point, a point of
curvature, along the right-of-way. I locate it. I then locate another
point, again on the right-of-way, on the lot I'm surveying. I check the
distance between these two points, and the distance is pretty good. I
decide to hold the line. I now want to rotate and translate the traverse
point I'm occupying to the coordinate system of my lot.
Solution:
I've created a fictitious job on paper to figure out how to do this. In
the field I'd use 20,000 N, 20,000 E on my backsight point. I'd use an
assumed bearing from that, and the distance I shot, to calculate coordinates
for the traverse point (point # 100). The POB on my calculated lot is point
# 1 (5,000 N, 5,000 E), which is also backsight point # 101.
Problem:
I'm unable to successfully rotate and translate one of my points. I'm using point
# 101 as my rotation point. My rotation angle is the difference between # 101
to # 100 and # 1 to # 4 (a point on my lot). My translation deltas (-15,000 N,
-15,000 E) is old point # 101 to new point # 1. My rotation point is # 101.
Data (before transformation):
# 1 5,000.0000 N 5,000.0000 E
# 4 5,105.4343 N 5,007.3475 E
# 100 20,068.5894 20,068.5894
# 101 20,000.0000 N 20,000.0000 E
# 104 (# 4) 20,105.4339 N 20,007.3485 E
Data (after transformation):
# 104 5,084.3779 N 4,936.3551 E
Regards,
Mark
Try this without the computer. Basic trig and a calculator. The error of your ways will soon become apparent.
> I'm unable to successfully rotate and translate one of my points. I'm using point
> # 101 as my rotation point. My rotation angle is the difference between # 101
> to # 100 and # 1 to # 4 (a point on my lot).
You should be using the difference between 101-104 and 1-4 as your rotation angle, not 101-100 and 1-4. 101 = 1, and 104 = 4. 100 just comes along for the ride.
The numbers aren't making sense. They are identical then a rotated point pops up.
1, 4 and 101, 104 have the same bearing between them which should be impossible and are essentially the same coordinates
I can say something is wrong but I can't say what, I assume 104 is field located and 4 is calculated?
Thanks for replying!
Procedure:
(1) Set traverse point # 100 20,000 N 20,000 E. Occupy it.
(2) Shoot distance to corner you want to hold. I shot 97.00.
(3) Assume bearing to corner you want to hold. I assumed S 45d-00'-00" W.
(4) Store corner you want to hold as # 101. Backsight it.
(5) Locate corners. Decide which one you want to hold. I will hold # 4.
(6) Rotate and translate the corners you located.
Data (before transformation):
# 1 5,0000.0000 N 5,0000.0000 E
# 2 5,013.5172 N 5,000.9420 E
# 3 5,066.5286 N 5,004.6363
# 4 5,105.4343 N 5,007.3475 E
# 6 5,131.8045 N 4,986.6802
# 100 20,0000.0000 N 20,000.0000 E
# 101 19,931.4106 N 19,931.4106 E
# 102 19,944.9281 N 19,932.3527 E
# 103 19,997.9392 N 19,936.0432 E
# 104 20,036.8445 N 19,938.7591 E
# 106 20,063.2175 N 19,918.0879 E
Transformation Parameters:
Old azimuth: 101 to 104
New azimuth: 1 to 4
Rotation angle: 359d-59'-58"
Rotation point: 101
Old point: 101
New point: 1
Delta N: -14,931.4106
Delta E: -14,931.4106
Transformation checks:
Distance # 101 to # 1 = 0.0000
Distance # 102 to # 2 = 0.0002
Distance # 103 to # 3 = 0.0043
Distance # 104 to # 4 = 0.0004
Distance # 106 to # 6 = 0.0047
Note:
Distance # 101 to # 1 should be 0.0000 if transformation was successful.
Thanks for replying! I used the wrong field procedure in my first post, so my coordinates for # 100 weren't correct. I added one hundred to my calculated points after I located them and before I stored them as field points.
Thanks for replying! My field procedure was amiss.
If you are doing this in a data collector, it may not let you rotate and/or translate an occupied or backsight point. I've found this in TDS Survey Pro. Bail out, reenter the program without specifying an occupy or bs point, then try your adjustment.
Why not try "resection"? creating your setup point from 2 known points.
Ken
What Ken said...
Use the Resection routine in the data collector.
Spectra Precision Survey Pro now calls this as Unknown Station Setup.
One word of warning: the routine will scale your measured distances between the two points to hold the record dimension between the points. The lower the precision of the actual location of the two points the more distant the computed location of the total station setup will be from where it actually is.
In other words, if the distance between the two points you are using for the resection are supposed to be 500 feet apart but by your measurements, they would actually calculate to be 499.9 feet, the routine will "adjust" the distance of your shots to hold that record distance between your resection points. If the precision is even lower it would result in the coordinate that is assigned for the location of the total station being further from where it actually is.
And as someone else said above, it would be a very good idea to understand the math behind the routine so you have some idea whether the results make sense or not.
