1What is Differential Leveling
Field measurement technique for determining elevation
2Bench Mark
Point of known elevation
4HI
Height of Instrument + BM
5h.i.
Local instrument height
7Vertical (plumb)
Line that follows the local direction of gravity
8Datum is
Level surface to which elevations are referenced
9Vertical Control
Series of interrelated bench marks established throughout a survey region
10Curvature
HIGH rod readings
11Refraction
LOW rod readings
12Turning Points (TP)
Temporary/intermediate bench marks
13Side Shots
Other points of interest
14Level Loop or Circuit ...
start and end are same point
15Level Section Traverse
starts and ends on different point
16Misclorsure
Difference of field elevation and known elevation
17Closed Level Loop Misclosure
difference of summed backlights and foresights for BM and TP
18Leveling Precision
- Repeating Measurements
- Checking BM
- Quality Equipment
- FOCUS
19Quantifying Low Precision Survey
- Lab
- Simple construction stakeouts
- 0.02√n
20High Precision Surveying
- Coefficients Order/Class
- function of total x distance leveled
- C = m√K
21OTHER elevation measuring techniques
- Taping- measure x
- relative elevation difference
- Barometric Leveling
- Trig Leveling
22Leveling Error
- Shift air pressure
- Storms
- Fluctuations
23What is a Traverse
Connected lines and angles with known values
24Characteristics of Closed Loop Traverse
- Easy Adjust
- Legs
- interior angles
25Characteristics of Closed Linear Traverse
- Challenging adjustment
- known orientation angles
- known coordinates
26what is the use of Traverses
- make & find property boundaries
- horizontal mapping
-find area enclosed
- earth work
- locations of proposed features
27forumula to calculate Closed Loop Traverse angles
(n-2) x 180
28Traverse Adjustment Steps (8)
1. angular misclosure
2. Bearing & Azimuth
3. Latitude and Departure
4. traverse misclosure & precision
5. adjust Latitude and Departure
6. Coordinates for station
7. Area (closed)
8. Adjusted Bearings, Azimuth & Lengths
29Closed Loop traverse Prefer
Bearings
30Closed Linear Traverse Prefer
Azimuth
31Misclosure formula
c = √Σ(Lat err)² + (Dep err)²
32Precision forumula
misclosure/perimeter
33what are the Adjustment Methods
1. Transit Rule
2. Compass Rule
34Transit Rule
angles more precise than distances
35Compass Rule
Same confidence between angles and distances
36Magnetic North is…
Dynamic
37Geodetic/True North are
defined by static poles
38Magnetic Declination is
Difference between Truth North and Magnetic North
39Magnetic Declination varies
- spatially
- time
40Isogonic charts dependent on...
1. time
2. spatially
41What is used to quantify magnetic declination...
42what is Agonic line
Zero declination
43Categories of Variability of Declination
1. Secular
2. Daily
3. Annual
4. Irregular
5. Local attraction
44Categroies of Declination Variablility: Secular is..
Large, Impossible to predict
45Categroies of Declination Variablility: Declination Daily ....
Varies 00°08"
50Characteristics of Geodetic Surveying
- earth curvature considered
- ellipsoid model
51Characteristics of Plane Surveying
- flat, horizontal region
- Lines of gravity parallel within region
52Where is Greatest Degree Confidence
angles measured along lines of sight
53Earth rotation angle is...
23° from vertical