- Orienteering
- What is it
- navigating in the 'real world' using a map (air photo)
- relate map - photo - real world
- determine bearings and distances from map
- therefore determine orientation & scale of photo
- Refresher
- Scale
- ratio of map / real world
- it is the blow-up / reduction factor
- example
- 1: 10,000 ...
- means real world shrunk by 10,000 times
- 1 cm on map = 10,000 cm in real world
- or ... 1 cm = ? m real world
- 2.5 cm map = ? m real world
- how to determine for air photo
- if have map ...
- find 2 features on map & photo ...
- determine RW distance using map ...
- then measure photo distance ...
- fill in the 2 ratios
- Direction
- bearings 0 - 360
- Douglas protractor
- place on map, N pointing up
- centre hole over starting point
- determine direction of line of travel
- Silva compass
- place on map, edge aligned with direction of travel
- twist housing until N (and black lines) parallel with N on map
- read top of compass
- Orientation of photo?
- compare to a map
- find 2 features seen on both
- determine bearing of line on map
- place protractor on photo and align with known bearing
- then simply find N
- in real world
- find 2 features seen on both
- take bearing in real world
- place compass (protractor) on photo and align with known bearing
- then simply find N
- Issues using a photo
- scale varies with topography
- tops of trees are displaced
- you are walking SD not HD