Review - Spatial Data

Review - Spatial Data
- Map Basics
  - Uses of maps
    - shows what & where
    - navigation
    - patterns, distributions, relationships
    - topography
  - Map components
    - map proper
      - bound by neatline
      - may have graticule
    - surround (collar)
      - title
      - date
      - publisher
      - datum/ projection
      - legend
      - scale
      - north
  - Types of maps
    - real (or virtual)
    - general reference
      - planimetric
      - topographic
    - thematic
      - vegetation/ timber
      - habitat areas
      - political
      - etc.
  - Mapping Systems
    - NTS
      - 1: 250,000 (e.g. 92G) - 4x4 grid; A - P
      - 1: 50,000 (e.g. 92G / 11) - 4x4 grid; 1 - 16
    - BCGS
      - 1: 20,000 (92G.011) - 10x10 grid; 1-100
      - 1: 10,000 (92G.011.3) - 2x2 grid; 1-4
      - 1: 5,000 (92G.011.3.2) - 2x2 grid; 1-4
- Georeferencing
  - unique description for location
  - Non-Metric (no measure)
    - placenames, landmarks
    - street address
    - postal code, phone exchange, census, etc.
    - issues
      - "local"
      - repeats
      - inadequate for natural landscape
  - Metric (measured)
    - Measured distance/direction from P.O.C.
    - Coordinates
      - Lat/ Long
        
        angles ... sphere
        
        ... but geoid ... use ellipsoid
        
        lat: 0=equator, 90=poles, N/S
        
        long: 0= prime mer., 180= int'l dateline, E/W
        
        DD MM SS ... DD.DDD
        
        NAD27 & NAD 83
      - UTM
        
        60 zones, 6 degrees wide
        
        zone 1: 180/174W -> goes east
        
        zone 30/31 straddle prime mer.
        
        each zone has its own "coord realm"
        
        equator = 0m N
        
        central meridian = 500,000m E
        
        true north vs. grid north
    - advantages
      - resolution
        
        coarse
        
        - UTM to nearest km or 100 m
        
        - simply provides general location (e.g. lake)
        
        fine
        
        - UTM to nearest 10 (or 1) metre
        
        - provides a specific location of a feature (e.g. tree or cave)
      - no uncertainty, but ...
        
        lat/long - specify E/ W & N/ S
        
        UTM - specify zone & N or S
    - interpolate coord.
      - consider "size of grid" (look at neatline)
      - 2 ratios
        
        partial dist. / "full grid" dist. (cm on map)
        
        X / "full grid" off neatline
- Map Projections
  - Distortion: shape, area, distance, direction
  - developable surface: plane, cylinder, cone
  - tangent vs. secant
  - standard lines
  - UTM in detail - as above
- Map Scale
  - it's a ratio (a reduction factor), word statement, scale bar
  - it's map/ real world, map/ real world, map/ real world ...
  - large vs. small scale
  - generalization
    - less detailed (accurate) ... smaller scale map
    - selection (omission)
    - combination
    - simplification
    - displacement
    - exaggeration
    - ... and smoothing
  - Units
    - metric (mm - cm - m - km)
    - imperial (in - ft - yds - mi)
    - conversions
      - 1 inch = 2.54cm
      - 1 mi = 63,360 in = 5,280ft
  - Problems
    - 3 cm = ??m on a 1: 50,000 map
      - 3cm / X cm = 1 / 50,000
      - X = 150,000cm = 1,500m
    - 7.5 cm = 1,500m, what is scale?
      - 8cm / 160,000cm = 1 / X
      - X = 20,000
      - 1 : 20,000
    - alternate thinking
      - 1: 50,000
      - 1 cm on map = 50,000 cm ground
      - 1 cm map = 500 m ground
      - 3 cm = ...?
    - map of known scale, find scale of photo
- Traversing
  - record: direction, distance & slope angle
  - calculate
    - HD
      - = SD * COS(slope degrees)
        
        COS = HD/SD ... HD as a % of SD
    - Elev
      - = HD * slope%
  - plotting
    - reduce HD to map distance
    - use Douglas protractor
- UTM Coordinates
  - draw & label the box
  - mark A & B
  - distance (pythagorus)
  - direction
    - ArcTan(ratio) to get degrees
    - add/ subtract from reference line
- Air Photos
  - EMR
    - wave energy: radio, micro, IR, visible, UV, x-ray, gamma
    - transmit, reflect, absorb, refract
    - atmos. window
    - spectral signature
  - activities
    - photo interp
    - photogrammetry
    - orienteering
  - stereoscopy
    - use binocular vision
    - view overlapping photos
    - form a 3D image
    - need
      - stereo pair
      - properly aligned
        
        PP, CPP, flight line, distance, align stereoscope
      - stereoscope
        
        lens
        
        mirror
  - photos
    - photo number (30BCC07018 #012)
    - flight line
      - endlap, side lap
      - drift, crab
    - geometry
      - similar triangles
      - photo / real world (PD / GD)
      - f / H
      - ... Alt = H + Elev
    - issues
      - scale varies with elevation
      - tops of objects are displaced ... hill tops are displaced
      - ... orthophoto - scale corrected and hilltops in right place
  - Problems
    - PD= 8.2 cm, GD = 810m, scale?
      - 8.2 cm / 81000cm = 1 / X
      - X = 9,878
      - 1 : 9,878
    - f=12", alt=24,000ft, elev = 300m, scale?
      - f / H = 1 / X
        
        got "f" (12" or 1'), need "H"
        
        H = Alt - elev
        
        H = 24,000ft - 300m
        
        1m = 3.28 ft
        
        300m = 984ft
        
        H = 24,000ft - 984ft = 23,016 ft
        
        1 / 23,016
- GPS
  - How it works
    - 24 SV's in 6 orbits
    - each SV sends a unique signal signal (pseudorandom code, a.k.a ...)
    - receiver "plays" code at same time
    - time diff. gives distance (speed of light)
    - 1 SV = surface of sphere
    - 2 SVs = hoola hoop
    - 3 SVs = 2 points ... one usu. silly, so 3 is all you need
    - but time uncertain ... so need 4th to deal with time error
    - ... just like in 2D we use 3 angles for triangulation
  - 3 segments
    - space
    - ground
      - 5 stations
      - monitor SV clocks & orbit
      - send corrections to SV's
      - SV's send correction + the pseudorandom code
    - receiver
  - Error/ uncertainty
    - clock (1-2m)
    - ephemeris (2-3m)
    - receiver (0.5m)
    - ionosphere (5m)
    - troposphere (0.5m)
    - multi-path (1m)
    - selective availability (100m)
    - PDOP (factor 3-6)
- Terrain
  - vertical datum
  - methods
    - hill profiles (Middle Earth)
    - hachures
    - layer tinting (bands of colour)
    - hill shading
    - spot hts
    - contours
      - index, intermediate, (supplementary)
      - labels uphill
      - gullies point uphill, ridges point down
      - hilltop/ lake @ 1/2 interval
      - points - interpolate ... partial / full
  - slopes
    - slope% = rise / run ... (or slope in degrees)
    - SD = HD / COS (slope degrees)
      - if slope is in % ... convert to degrees with ArcTan
      - or, if have Elev ...
        
        pythagorus
  - profile
    - use edge of paper (or draw lines straight down)
    - transfer to graph
    - vert scale is usu. exaggerated
    - can use for visibility analysis
  - grade line
    - to plan trails & roads
    - steps
      - determine target spacing btwn contours
        
        find HD for contour interval of map
        
        e.g. 15% and 20m contours
        
        15 / 100 = 20 / ??
        
        ?? = 133m
        
        convert to map dist.
        
        133 m on 1 : 20,000
        
        1 / 20,000 = Xcm / 13300cm
        
        x = 0.67cm ... = 0.7 cm
      - mark points btwn contours ... then connect the dots
- GIS
  - components
    - computer (hardware & software)
    - geographic data (spatial & attribute)
    - functions
      - input / maintain: input, edit/update, transform
      - analyze
        
        query
        
        buffer
        
        overlay (clip, erase, update, union)
        
        routing (911)
        
        catchment areas
        
        terrain analysis
      - output: screen, web, paper
    - organization/people: Tech, Analyst, Mgr.
  - definition
    - integrated components
    - operate on spatial data
    - generate new information
    - help with decisions
  - data models
    - vector
      - map: coordinates
        
        single = point feature
        
        connect a string = line feature
        
        connect a closed string = polygon feature
      - table with descriptive data
      - 1 : 1 features : row in table
    - raster
      - spatial data - in a grid
      - attribute data - #'s in the grid
      - resolution - real world units
- Satellite Imagery
  - Flow of EMR
    - EMR from Sun
    - atmospheric window
    - stikes object (absorption / reflectance)
    - back to sensor - "brightness of band" gets recorded
    - Satellite in polar orbit
    - data beamed to Earth
  - Image
    - pixels (Landsat 30, SPOT 10, Ikonos 1/4)
    - number in pixel = "brightness" (reflectance) 0 - 255
    - all high = white; all low = black; all middle = ??
  - Spectral Signature
    - unique reflection of RGB & NIR
    - veg: lower B&R, higher G & NIR ... veg is not green
    - water: lower R & NIR, higher (but still low) B & G
  - Composites
    - True
      - R = R
      - G = G
      - B = B
    - False
      - R = NIR
      - G = R
      - B = G