Mapa mental

CEG2712

Julia Smith CEG2712 Inglês

Conteúdo do mapa

CEG2712

Maps
- OS Maps
  - Os= Ordinance survey
  - Scales
    - 1:10,000
      - Everywhere
    - 1:2,500
      - Rural areas except mountians and morrlands
    - 1:1,250
      - All urban areas
    - printed maps at these scales can only be drawn to around 0.3 mm accuracy witch trans lates to a 0.4 m possible error and smaller features such as man hole not being included
  - Linked to Land Registray
    - ~6 months latency in updating maps
      - Major city projects may have updated maps sooner and small rural area updates may take longer as a result the data stored may not be truely representative of the area
- Can be paper but more commonly stored as a digital data base and ploted using GIS
  - GIS= Geograpic information systems
  - Data uses angles, bearings, distances and coordinates of POI and features
    - Points of intrest = POI
- National grid maps
  - Use Eastings and Northings
    - Eastings = X direction Northings = Y direction
  - Origin ~100 km west of the Scilly Isles so all coordinates for the UK are positive
  - Take in to account the Earths curvature
- Due to problems with detail and accuracy of OS and NG maps new serveys are undertaken for each new project
  - NG= National grid
  - Commonly uses project scales
    - 1:200
    - 1:100
    - 1:50
    - Scale used depends on size of project and detail required
  - Site spasific grids DO NOT need to account for earths curvature if site is under 10 km
    - If using NG and doing plane trig an arror of 8mm per 10 km is possible
      - Proof r= average radius of earth = 3680 m s = length anlong curve of earth l = plane trig length (theta) = angle s=r(theta) assume : s=10 km (theta)= s/r = ~ 0.0981 degrees r(tan(theta)) = l = 10000.0088m Therefore : 10km error could be up to 8mm form calculations
Total stations
- Used to electronically measure angles horizontal and vertical and hieghts and distances
  - Requires line of sight
- Can be used to establish horizontal and vertical control networks
  - Control network = a set on known point out side of the project site that do not change where the exsact coordinates and hights are known maybe be local, regional or national
    - Methords of establishing a control network
      - Triangulation
        A methord where all angle between points in the network need to be known and one length
      - Trilateration
        A methord where all distences between points in the network need to be known and one angle
      - Network >>>
        Combination of other methord uses both and angles and distances do not need all three angles or distances per triangle allows flexibility
        Commonly used methord
        Set up useing traverseing/ GPS/GNSS
- Used for detailing feature and points in an area of intrest
  - Process of quickly gathering lots of data about an areas main features using a prsium and pole
- Used to set out planed lines and shapes before a building project can be begin
  - Setting out involves marking points with pegs and nails that have been measured off useing an reflector and total station
Coordinate refference systems
- Examples
  - Global
    - Lat/long
      - Latatude =north to south Longditude = east to west
      - >>> >>>>
    - WGs84
  - National
    - UK national grid
      - uk all positive and origin ~100km west of the sille isles
      - >>>>>
        More in geodesy
  - Local
    - Site grid
      - Planar computations
        (delta)Eab=Eb--Ea=LabSin((alpha)ab)
        (delta)Nab=N--Na=LabCos((alpha)ab)
        Lab=sqrt((delta)Eab^2+(delta)Nab^2)
        (alpha)ab=Tan^-1((delta)Eab/(delta)Nab)
        Basic trig using North as X and in surveying notation
        Calculator will only give values between -90 and +90 both positive WCB = value on calc -N WCB = Value on calc +180 -E+N WCB = Value on calc + 360
        <<<<
        >>>>
        Tan((alpha)ap=((Ep--Ea)/(Np--Na))
        Tan((alpha)bp=((Ep--Eb)/(Np--Nb))
- Plane coordinate systems
  - Rectangular/ Cartesian
    - coordinates in terms of X and Y
    - Most frequently used in plane surveying computations
  - Polar
    - Coordinates in terms of r and (theta)
  - Conventions
    - ^^Simalar to maths with north as a reference and not X ^^
      - N= North : X E= East : Y O= origin P=Point of intrest l=Length :r (alpha)=bearing : (theta)
    - Angles measures clockwise from north
      - North can be GRID, TRUE or MAGNETIC
        GRID= the direction of the north south lines on a grid  TRUE= the direction of the geographical maridian towards the north pole MAGNETIC= Direction of the north magnetic pole 
- WCB's
  - WHOLE CIRCLE BEARINGS
  - Notaion is important
    - (alpha) = bearings (theta) = angle subscripts: At - From - To
  - North = 0 and 360
  - Units = DMS
    - Degrees Minutes Seconds
  - ALWAYS CLOCKWISE
  - Forward and back wards bearings
- Fundamental to mapping gives scale and orientation to features
Common Procedures
- Levelling
  - A process to find the high of a given point in respects to a known point or datum
  - Equipment needed
    - Tripod
    - Level
    - Staff
    - Recording sheet
    - Change plate
    - Recording equipment
  - Procedure
    - Leveling Procedure Simplifyed
  - Taking measurements
    - Have the staff waved back and forth while vertical and read off the staff the smallest measurement observerd
  - Common errors
    - Paralax present readings inacurate
    - Equipment incorrectly leveled
    - Reading taken from cross hair markers
    - Staff not kept vertical
    - 12sqrt(k)mm
- Traverseing
  - Link traverse= Points in a line (used for mining and tunnelling) Loop Traverse = Point form a loop (most commonly used)
  - Common errors
    - Equipment not correctly leveled
    - Off centre aim of the total station
    - Poor reflection in the reflector
    - Distance confussion
    - Equipment not centered
    - 60sqrt(k)mm
  - Equipment needed
    - Total station
    - Tripod
    - Pole
    - Reflector
    - Recording equipment
  - A process used to to establish control networks using known points, angle and distances
    - Loop angle checks
      - SUMIA=(n-2)*180
        IA= Interiour angles
      - SUMEA=(n+2)*180
        EA=Exteriour angles
  - Procedure
    - Fixed three tripod procedure
      - Swaping intruments to reduce the number of times tripod set up is required
    - 1. measure and zero on to reference point
      - 2. measure multipul rounds of horizontal angles useing both faces
        3. Measure multipal distances and VA's using both faces
        4. Measure instrument and target hight
    - Start with the back station turn angle clockwise to forward station
    - Booking sheet explained
      - Example sheet
      - one sheet = one angle
        One traverse can require many sheets
      - face left = face right + 180
      - HA: mean then reduce VA: reduce then mean
        HA = horizontal angle VA = vertical angle Reduce = take one bareing from the other
      - All details should be filled out plus any extra note incase there are problems later on
    - Traverse computations
      - Example sheet
      - Bearings of all lines
      - Horizontal distances of all lines with slope adjust ment >>
      - (delta)Eastings
        Difference in eastings
      - (delta)Northings
      - Coordinates of each point
      - Misclosures
        Differences in computed and real values
        Eastings and Northings
        Computed - Known
        Sign matters!
        Positional
        Distances difference=sqrt((eastings misclosure)^2+(northings misclosure)^2)
        Bearing of difference=arctan(easting misclosure/northing misclosure)+ AIN
        AIN = Alterations if needed
        Propotional
        Positional misclosure/total length of traverse
        Sated as a ratio of 1:xxx
        Accetpable misclosures>>>
  - Hight abstraction sheet example
- Detailing
  - Fixation of detail features with respects to the horizontal and vertical control
    - Hard Details
      - Walls paths and buildings ect
    - Soft details
      - Trees, bushes and grass paths ect
      - recording trees requires 2 measurements  Center and edge
  - Methords
    - Radiation
      - lots of points gathered form one station
      - Diagrams and stings needed to keep track of data can be 100s of points per station
        String list of feature order and codes 
    - Offsets
      - Measures details with a tape two lines to a point
    - Grid levelling
      - Set out grid of plottable and numbered points and use spirit levelling more detailed highs but time consuming to set up
    - Sectioning
      - Used on linear works for precise hights Longitudinal lines cut the project in to section and levelling is preformed along the lines for points where gradients change and edges natural or man-made final plot often on an exagurated scale
- Error analysis
  - <<Blue = Presision
  - <<Red = Acuracy
  - Human errors
    - Transposition of numbers
    - Mis-identification
    - Easiest to fix by hand
  - Systematic
    - Offset from point
    - Zero error
    - Limits accuracy
    - aging of equipment
  - Random
    - Interpolation between devisions
    - Placements of tapes
    - Bisection of target
    - Centreing of tripod
    - Size and nature quantified by standard deveation whitch can be uses to identify out liers to improve results
      - Effected by instruments used, obserser skills and location conditions
Geodesy
- Datums
  - a particular choice of coordinate axies with a set origin
  - Must be realised by fixing the coordinated of some point
  - Site grid may be alignet with main features EG two walla of a building meaning that north is not used
  - Zero hight is often set as a plane EG mean sea level
  - Large areas (over 10km) MUST take in to account earth curvature
  - International datums
    - due to irregular shape of earth ellipsoids are often used
      - Due to ellipsoid shape flat maps require projection
        Great Briitain uses the transverse mercator projection
        World map
        For UK north south lines converge so UK National Grid is used
        F=F0(1+(((E-400000)^2/(2R^2)))
        F0=projection factor on centreal maridian
        F=National Grid Eastings of a point
        R=radius of the ellipsoid (usaly R=6380km)
        Scale maintained along 2 maridians
        North and south
        Equator
        Shape maintained making it a orthomorphic projection
        Once points have been projected plane trig can be used
    - mean sea level is a geoid mathmatically so is represented with an elipsoid
    - earths average radius = 6378km
- Hight datums
  - Ordenence datum Newlyn for the UK
    - Defined by 190 fundamental bench marks all over the uk
Transformations
- Xp=s(xpCos(theta)+ypSin(theta))+(delta)X
- Yp=s(-xpSin(theta)+ypCos(theta))+(delta)Y
- Types
  - Shift
  - Rotation
  - Scaleing
  - Requires 4 parameters s, (theta), (delta)X, (delta)Y
Rail set out
- Cross section
- Alignment
  - Tangent
  - HIP
    - Horizontal intersection point
  - Chainage
    - Distance along alignment
  - Composite curve
    - Approching stright
    - Approche tangent point
    - Approching transition
    - ARC
      - Arc formulas
        Turn angle = (theta) = s/R
        Radius = R
        Deflection angle = (ldelta) = (theta)/2 = s/2R
        Chord length = c = 2RSin((theta)/2) = 2RSin(ldelta)
        Length TI = RTan((theta)/2)
        Arc length = s
    - Departing transition
    - Departing tangent point
    - Arc shifts away from the HIP to allow for transition curves
    - Transition radius decreases form infinity to the radius of the curcular arc
    - Transitions
      - Reasons of use
        Gradual change of acceleration
        Comfort
        Safety
        Allows for change of superelevation
      - Definitions
        Rate of radial acceleration is constant
        Rate of change of centrifugal force is constant
        Clothoid spiral maths
        (phi)=L/(2R)
        (ldelta)=(phi)/3
        Rate of change of curvature is constant
- Elevation
- Design criteria
  - Design speed = V(km/h) or v(m/s)
    - Based on 85 percentile speed
  - Rate of change of radial acceleration = q
    - In range of 0.2 to 0.6 m/s^3 0.3 recommnded
  - RLt=v^3/q
    - R= radius Lt = transition length v= design speed in (m/s) q= radial acceleration
  - (phi)=l^2/2RLt
  - S=Lt^2/24R
    - S=shift Lt= Transition length R= radius
  - C=Lt/2
  - (R=S)Tan((phi)/2)+C
    - R= radius S=shift (phi)=turn angle C= Transision addition