From A to B

by Ray Jones and Kiran Kedlaya (construction by Ray Jones, Daniel
Vlasic, Tom Buehler, Chris Morse)

Answer: YARDSTICKS

The "appropriate unit" is of course the smoot (5 feet 7 inches); as a
hint, the last photo includes the picture of the Smoot incident in
Building 56.  Each distance is an integral number of smoots (to within
an inch or two); reading these numbers as letters spells

POINT FIVE THREE SEVEN SMOOT LONG RULERS

(The fact that the letters A-D do not appear in the clue phrase is
unintentional, but funny. Mwa ha ha.)

0.537 smoots is about 36 inches, so this defines YARDSTICKS.

For reference, here is where each photo (or photo pair) was taken:

Dibner building/Copernicus statue
Plaza outside MIT Medical
Lobby 2
Enclosed courtyard within Building 14
Front of Simmons
Dertouzos Amphitheater (Stata Center)
Building 34, first floor
MIT Chapel
Walkway between Buildings 16 and 26, second floor
Between Tang Residence Hall and New House
Building 10 from Killian Court
Senior House
Building 9
Behind Student Center
Student Center, first floor
Building 5, basement
Z-Center
Vassar Street in front of Building 38
Killian Court
Baker House
Walker Memorial
President's Courtyard
Food trucks area
Lobby 6
Dewey (Sloan)
Killian Court, by Building 2
Building 34, fourth floor
Lobby 13
The Dot
Infinite Corridor, from Lobby 7
Cashier's Office to Lobby 10
Behind Building 34
Astroturf
Building 56