Direction

Direction
- North - what is it?
  - true
  - magnetic
  - grid
- Plot a bearing
  - Douglas Protractor
    - align with "grid" (i.e. graph paper)
    - centre over "spot" & mark
    - mark brg at edge
    - connect the dots (light pencil line)
    - draw to proper length
  - Silva Compass
    - align edge of compass btwn features
    - twist compass housing until black lines align with N-S
    - read top end of compass
    - watch for "180 error"
- Grid North
  - use for UTM coordinates
    - interpolate
    - place a location
  - use for direction if a correction is made
    - determine grid brg
    - then adjust (+ or -)
  - OR ... ignore grid and use lat/long (neatline) and draw true N lines
- Triangulation
  - a.k.a. "Resection"
  - determine location using 3 bearings
  - find 3 features visible on map (photo) and real world (e.g mtn. peaks)
  - determine bearings to features
  - but plot the 'reverse bearings' on the map
  - plotted triangle provides indication of uncertainty (error)
- Orient a Photo
  - "putting a N arrow" on the photo
  - photo & map
    - locate 2 features visible on both the photo & map
    - determine bearing btwn features on map
    - "plot bearing line" on photo
    - determine N from this line
  - photo & real world
    - same as above, but replace "map" with "real world"