To choose an LED area light distribution for poles that are already in place, start with the ground area each pole has to cover. Then pick the optic whose photometric pattern covers that area at the same pole height, spacing, and aiming.
Wattage and housing style don't tell you where the light lands. Two outdoor lighting fixtures with the same wattage can light very different parts of the lot.
The steps below go in that order. First you define the target for each pole. Then you see how different patterns spread light, and last you compare real photometric data on your actual layout.
Start With the Ground Area Each Pole Must Serve
Every pole has its own job, and that job depends on where it stands and which way the fixture faces. For each pole, mark the edges of the ground it should light. Note whether that area surrounds the pole, sits mostly on one side, or fills a corner.
Interior Poles
An interior pole usually lights ground on several sides, out to the areas its neighbors also cover. So you are asking how far light needs to travel in each direction to meet the next pole's pattern. The word "interior" doesn't pick the optic for you. The target directions and the candidate's photometry decide it.
Perimeter and Corner Poles
On an edge pole, the target may run inward toward the lot, along the boundary, or across a corner. The installed aiming direction determines which side of the pattern reaches the pavement target and which side faces the property line. A corner pole has its own shape, so don't assume an edge-pole choice fits it. Once you know each pole's target, you can narrow down parking lot lights to candidates whose data you can actually compare.
How Distribution Patterns Change the Ground Pattern
The distribution controls which directions light leaves the fixture, and that sets the shape it makes on the pavement. DOE's distribution explanation describes photometric distribution as how much light intensity leaves a luminaire and in which directions. It also says the right distribution depends on the space design, the lighting results you want, glare control, and aesthetics. The same guide compares three sample patterns:
| Pattern | Directional spread | Guide's stated implication |
|---|---|---|
| Broad batwing | More light at wide angles than directly below | Can allow wider spacing and more even ground lighting |
| Cosine | Highest intensity directly below | Can meet an average target but might miss desired uniformity |
| Intermediate | Between batwing and cosine | Use only in select situations |
These are DOE's sample shapes, not the IES Type I to V labels found on spec sheets. In the guide's context, parking-lot luminaires tend to be mounted 20 feet or more above the ground and 100 feet or more apart, and DOE's typical mounting and spacing context is why it calls wider distributions ideal there. In practice, a lot with widely spaced poles that needs light far out between them is a good reason to test a broad pattern first. If the target sits mostly right under the pole, a cosine-like pattern puts light there, but check whether it keeps the lighting even. None of this decides the optic for one particular pole.
Compare Photometric Data Under the Existing Installation Conditions
A candidate is a better fit only when its photometric result covers your target under your pole conditions. DOE's photometric-report guidance says polar plots show the pattern of emitted light, and outdoor area luminaires are classified by the pattern they make on the ground. To compare candidates fairly:
- Set the baseline site layout once: pole locations, spacing, mounting height, fixture orientation, and the applicable project coverage criteria.
- Get photometric files for each candidate in the configuration you would actually install. If the files are new to you, it helps to learn how to read an IES file first.
- Run every candidate on the same ground grid, scale, and calculation settings. A lighting layout tool or a design calculation keeps those settings the same for each option.
- Check each result against the target. Look at whether light reaches the edges, how even it is between poles, and how much spills past the boundary. If no candidate covers the target, try a different distribution before changing the light output.
Don't pick a winner from the average alone. DOE's illuminance limitation notes that average pavement illuminance doesn't account for disabling glare that reduces visibility.
When a Replacement Stops Being Like-for-Like
A coverage comparison is only valid for the conditions it modeled. If you change pole spacing or mounting height, the pattern lands on a different footprint. If you re-aim a fixture, a different part of the pattern now faces the target. Moving a target boundary, such as adding a drive lane or pulling light back from a neighbor's lot, changes the area the light must cover. When any of these change, run the candidate again against the new layout instead of reusing the old result.
FAQs
Does matching the old fixture's wattage keep the same coverage?
No. Wattage tells you the power the fixture draws. It doesn't tell you where the light goes. Coverage comes from the distribution and the installation conditions, so compare photometric results instead.
Are DOE's batwing and cosine patterns the same as IES Type III or Type V?
No. The DOE guide says its samples should not be confused with the parking and roadway Type I to V classifications. Use the IES type on a spec sheet as a starting label, then confirm with the fixture's photometric file.
What should I look for in a polar plot to limit glare?
The DOE fact sheet suggests looking for reduced intensity at vertical angles from 70° to 90° to help avoid glare and light trespass. It also suggests little or no intensity from 90° to 100°, the angles that contribute most to skyglow.
Can every pole in the lot use the same optic?
Sometimes. Interior, edge, and corner poles often have different target shapes, though. Model each pole position with the candidate optic. If one optic covers every target, the layout works with a single optic. If not, mix optics where the results show you need to.
