Transcript controlling intermediate corners

Controlling Intermediate Corners
Instructor:
Dennis J. Mouland, PLS
© Witness Tree Consulting, Inc., 2011, All Rights Reserved
Course Objectives
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Define CIC’s for surveying purposes
Familiarize with background of various CIC’s
Discuss evidence analysis
Review use and application of CIC’s
Examine methods for restoration of lost CIC’s
The textbook:
www.blmsurveymanual.org/errata
Define
• What was the normal “level of control” set by
the GLO?
– Section and Quarter-Section Corners
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These are controlling, but intermediate…….
Intermediate to the normal level of control
But still control something
Line, and most proportioning
Some CIC’s exist due to procedure
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Meander Corners
Closing Corners
Crossing Closing Corners
Subdivisional Corners set previously
Others due to field conditions
• On-line Witness Corners
• Line Trees
• Witness Points
How do we know they exist?
• They must be in the
official GLO/BLM record
• Always in the notes
• Sometimes also shown
on the plat
• If they were noted, you
MUST look for them
• If found, they MUST be
used
Chains
22.46
A pine, 36ins diam.
What CIC’s will do to your survey
LT
1/4
WP
RECORD
LT
Lost 1/4
WP
MEASURED
We will discuss some of the CIC’s in detail:
Meander Corners
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Why set to begin with?
What is a meander line?
Why needed today?
If found, how does it control line?
Do we use it in proportions of lost corners?
Do we use it to set subdivisional corners?
If lost, should it be reset?
2009 Manual
• “A meander corner is established at every
point where a standard, township, or section
line or special survey boundary intersects the
OHWM of a navigable stream or other
meanderable body of water.”
(3-173)
MC’s
Meander Corners
• Found?
• Use to re-establish
meander line itself
• Use to fix alignment at
that point of section
line
• Use to set lost corners
on section line
• Use to proportion
subdivisional corners
along section line
• Lost?
• Must be re-established
to determine any
riparian issues
• If there has been
erosion or accretion,
the original MC position
must be determined
AND a new MC set at
the current OHWL
Lost ¼ Corner:
Lost MC:
26.29 (R) = 8.10
26.44 (M)
X
48.13 (R) = 8.10
48.08 (M)
X
X= 8.15
X= 8.09ch
On-line Witness Corners
• Why do WC’s exist?
• What about off-line WC’s?
• New policy in the 2009 Manual which aligns with
BLM internal policy
• Always controls the alignment
• Use differs between section corners and
quarter section corners
True Story
WC Sec. Cor.
Private Land
National Forest
¼ Cor.
Where Witness Corners might be a good idea!
40.00
WC 1/4
1/4
WC 5.00
5.024
WC
40.00
WC
Record
Measured
Result
40.00
40.00
40.00
WC Section Corner
40.00
40.00
Brg Brk at Sec Cor
40.00
WC 5.00
Record
Controlling bearing
pushed through at
5.00 chains
(Record)
40.00
40.00
WC
Result
Line Trees
• Must be called for in the notes, and cite
species, diameter, and distance to the nearest
link.
• Courts have ruled that they are monuments of
the original survey, which causes an angle
point in the line.
• Used for proportioning lost corners and
subdivisional corners. See BLM 6-28.
40.00
47.54 = 7.54
47.45
X
M= 47.45
Proportion for 1/4
1/4
7.54
¼ LOST
LT 32.46
S1/16 to be set
M=32.40
Record
32.46 20.00
32.40
X
Measured
Witness Points
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How differ from Witness Corners?
Sometimes referred to as “artificial line trees”
Utilized the same as line trees
Control line and alignment for lost corners and
subdivisional corners
Closing Corners
(2009—7-45)
• When an original closing corner is recovered off
the line closed upon and the new monument is
established at the true point of intersection, the
original position will control in the proportionate
restoration of lost corners dependent upon the
closing corner. In a like manner the positioning of
sixteenth-section corner(s) or lot corner(s) on the
closing line, between the quarter-section corner
and the closing corner, will be based on the
measurement to the original position of the
closing corner.
1.21
True section corners at intersection points
Proportions go to original CC positions
CC
CC
1.21
2.06
N1/16ths to be set
1/4
1/4
Lost 1/4
CC
Sec Cor
CC
Fd. 0.28 links north of twp. line
R=40.27
M=40.22
40.27 = 20.27
40.22
X
1/16th to be set
40.27 = 20.00
40.22
X
¼ Cor.
MINUS 0.28 = 19.96
X=19.975
¼ Cor.
X=20.24
Crossing Closing Corners
• Closing corners in some cases have been
established where a line of the survey crosses
previously surveyed claim lines (section 3-74
“Intersecting and Terminating Section Lines”).
These corners are established after a
retracement of the line intersected and
monumented when administratively required.
In the past, these corners have been termed
“crossing closing corners.” (2009—7-48)
CCC’s
• Will bend lines if it controls the line when
created
• Can be used to proportion lost corners if it
controls:
– Non-rectangular corners
– Subdivisional corners
– Lost PLSS corners
When you find a CIC………
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Remonument as an AP
Take accessories
Make the details part of your record
Where on the line trees?
If they are lost………
• Was it ever retraced and shown off-line?
– Re-establish by proper method (7-34)
• Never used by a survey?
– May not need to be re-set
• MC’s always should be re-set
• CCC’s usually should be re-set – B/B intersect
• WP still needed?
• CC’s adjusted once: then treated as equal
Rec.
Measured
Remon as an AP
Take accessories
Conclusion
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CIC’s exist in the field
You must search the record for their existence
You must search for them in the field
You must use them as appropriate control for
the line as is, lost corners, or subdivisional
corners to be set
• Their use is not optional
• They will change your survey results
CONTROLLING INTERMEDIATE CORNERS
© Witness Tree Consulting, Inc., 2011, All Rights Reserved