How To Write Up Calculations

For Full Credit In Aerial Photography and Remote Sensing

(and to avoid embarrassing and expensive errors anytime you make a calculation)

 

1.       Write down the equation that you need to solve the problem 

RF = f/H

If you need to reformulate the equation for the problem at hand, show what you did.  For example if you know that scale and the focal length and are trying to find the flying height  write

      RF = f/H

      H * RF = f

      H = f/RF

 

2.       Write down the actual measurements you make on images or maps. Label the number with a description and units.  If the measurement is one of the variables in the equation, include that in the description

d = parallax displacement, 0.2 in from base of building to top

                        or

235 dots in urban areas

 

3.       Write down any additional information you will use, with units and source

H = 3000 ft flying height, given on photo

RF = 1:3500 calculated last week

 

4.       If you have to make a calculation to derive a variable, show the steps

dP = distance between bases – distance between tops

      = 2.35 in - 2.21 in = 0.14 in

 

5.       Write out the equation with all your numbers and their units

RF = 6 in/20,000 ft  or 0.5 ft/20,000 ft

 

6.       If you need to do unit conversions at any point, show your steps and the cancellation of units.

h = 24 in. *  1 ft/12 in. = 2 ft

 

7.       Write your answer in it’s final form, with units.  And check to see that it is reasonable!  We are measuring real objects.  If you have a house that is 300 ft tall, or a lake that is 100 sq. ft.  something is wrong in your measurements or calculations. 

 

8.       If you are doing the same calculation several times in the same problem or on the assignment, you can take some shortcuts in the above, but always show any new basic raw measurements and give a reference to the complete description.

in the same way, with d = 0.3 in. and r= 4 in.

h of building 2 = 0.3 in / 4 in * 3000 ft

                                    or

as in 3. above with d = 0.3 in …..

 

9.      Be careful with equals signs. 4/5 = 8/x = 10 is not correct.  Use arrows to show that one calculation or equation leads to another  4/5=8/x  → x=10.