Many commonly-occurring lighting applications are mounted on a tall pole. Some are cantilevered, others are pole-top.
For cantilevered fixtures, omit the pole, and focus the analysis just on the fixture:
For post-top applications, include part of the pole, but cut it approximately to a length three times height of the fixture:
Construct an enclosure around the light, and center it horizontally within the enclosure. The size of the enclosure should be based on the size of the device, as shown below.
The side view is shown on the left; the front view is shown on the right: