CALCULATIONS
distance
map distance= distance x scale
True bearing
draw line between 2 points
~start at 1st given point,draw a straight line through it
measure using protractor
MAGNETIC DECLINATION
1 difference in years
2 mean annual change
3 total change=
diff in yrs x mean ann. change
4 add total change to 1st years magnetic declination
(+W -E)
MAGNETIC BEARING
true bearing + magnetic declination
measure TB
diff in yrs
mean annual change
total change yrs x change
add / subtract for MD
Tb + MD
coordinates
latitude S move down
longitude E. in RSA move to right
use 10 sec intervals
why does magnetic bearing change over time?
...
VERTICAL AERIAL PHOTOGRAPHS
taken directly above surface
@90° angle
bigger scale
OBLIQUE AERIAL PHOTOGRAPHS
pic not taken vertical to the ground,
taken @ an oblique angle
HIGH OBLIQUE
big area
distorted image
LOW OBLIQUE
shows specific area
clear images
SHADOW ON ORTHOPHOTO
indicates time long shadow @ day
look at trees and buildings
SE after 12:00
SE before 12:00