LED Display: Understanding Led pitch, resolution, viewing angle and distance
Let's assume that your LED segments are square size.


LED pitch: the distance between LED centers. If LED segments are arranged tight (side to side) - the pitch will be equal to the size of the LED.
Display size: - will depend on the LED size and the amount of the LEDs in rows/columns.
Viewing angle: - tells you at what range of angles you can view to still see the light emitted from the LEDs. If you noticed, the LED signs on the highway - you can read them from far away, but as you approach, the viewing angle increases and eventually you can not see anything (colimated ligth).
Resolution: - is straight forward - the higher the resolution the better/smoother you can represent fine parts of the image/letters. The minimum resolution depends on what you want to display. In the figure below, assume that you have the same size display. Since the size of LEDs is different in each case, the amount of them is also different. Consequently, the resolution is different as well. To represent letter "o" all cases are good enough, but if you wanted to represent more letters in the display, that is, a finer object, the display with the nigher resolution (on the left) would likely to be more successful.





Distance: probably means the maximum distance at which you can see (resolve) the letters/features on the display. Thus, for larger distances you will need larger objects on the display, and/or larger display.


The design of a display will depend on all of the properties above. There will be a trade off in these parameters. Given the requirements, some of these parameters will be fixed, and the other parameters will be derived based on these constrictions. For example, if available LED size is 10x10cm and you want your display to be 5.2x1.2m, you will need 52x12 LEDs. This means that your resolution will depend on those constraints and be limited to 52x12 pixels. 

For your appliction, I would take the following approach:


Decide how big should be an image, so it can be well seen from 200 meters away.
Decide the minimum amount of pixels needed to reach desired "smoothness" of the image.
Given the size from (1) and number of LEDs from (2), you would know what size of LED you need.