Tag for solar panel tracking (fixed, single-axis or dual-axis)

Hi all,

I’m working on mapping solar power for Global Energy Monitor, and we would like to record the existence and type of solar tracker for each installation. I came across a previous tagging discussion about this, though the topic shifted towards heliostats vs. photovoltaic panels and I didn’t get a clear answer. Is there an accepted tagging scheme for solar tracking?

I came across the key solar:tracking=* (taginfo) which seems to be what I’m looking for, though it has no documentation and only a handful of mappers have used it. There are about 2000 instances of solar:tracking=dual, and 100 instances of solar:tracking=2-axis (which appears to refer to the same thing), but no other values are recorded.

As I map, I’ll be using the following tags for now, though if there’s consensus on something different, I’m willing to mechanically update what I’ve worked on:

  • solar:tracking=fixed for solar panels that do not rotate
  • solar:tracking=single for solar panels that rotate on one axis
  • solar:tracking=dual for solar panels that rotate on two axes

Though I have a couple questions:

  • Which value is better for solar panels without trackers: =fixed, or =no?
  • Other relevant tags have a generator: prefix. Should this key be generator:solar:tracking=* instead?

I’m not closely familiar with the topic, but would it make sense to have the orientation of the axis (horizontal/vertical/tilted) reflected in the tagging?

That seems reasonable. Though single and dual would still be useful when additional information about the solar tracker is unavailable. This would give us the following values for solar:tracking=*:

  • fixed (or no?)
  • single if axis orientation unknown
    • horizontal
    • horizontal_tilted
    • vertical
    • tilted
  • dual if axis orientation unknown
    • tip-tilt
    • azimuth-altitude

I’ll write up a formal tagging proposal soon and link it here.

I’d use single_axis and dual_axis or clarity’s sake, and probably subtag the more detailed values.

For fixed panels I’ve never found a suitable key name to capture the angle of tilt (or none for panels laid on flat roofs). It would be nice to agree such a tag. I think we have used tilted=no for such panels, but there are plenty of panels on industrial buildings where the angle relative to the vertical is quite shallow, whereas most house roofs will be roughly 30-35 degrees which is close to optimal tilt for the UK.

I’ve updated the proposal to the values single_axis and dual_axis accordingly.

I’m not convinced this is necessary. A gravel road could be tagged as either surface=gravel or surface=unpaved, but one is more specific than the other, and it would be redundant and more labor-intensive to require such roads to be tagged as both “gravel” and “unpaved”. All horizontal solar trackers have only one axis of movement—we don’t need a separate tag to record this.

Feel free to write a proposal :wink:

no thanks, I may document what is in use.

There’s a need, some in use tags. What is needed is not a proposal, but more suggestions for the actual text string to use for the key. At the moment tags in use are tilted=yes|no, tilt=<angle>, tilt_angle=<angle> and probably a few more. azimuth is just too obscure. tilt_angle may be more consonant with related tags such as roof:angle, glideslope_angle, camera:angle etc., OTOH tilt is used as a key suffix for streetlights (light:tilt, lamp:tilt)

tilt=n would be fine to me. Referring to light:tilt for street lamps panel:tilt=* might do it too if insisting to relate tilt to the article it refers to.

For those following the sun recently started using heliostatic which could be heliostatic=yes/no or direction=heliostatic, JOSM expecting a numeric value though for direction. With fixed I’d figure the vertical angle is probably steeper the more northern one gets (on the NH).

NB: Someone in the UK was hot on just tilt= where the hotspot is per Taginfo and sampling a dozen, they seem to have gotten tilt=10 quite a lot, strange for such a northern location.


Yes that is stick2 who got involved in mapping solar power some time after we’d started the main UK project. They were the person who tried to map angles first: partly IIRC because there are a lot of panels on flat roofs in that area.

Note, most solar power tags will show hotspots in the UK because we have mapped nearly half a million rooftop panels, with about 35% with rich metadata. An angle of 10-15 degrees will be about right for panels mounted on larger industrial & farm buildings (such as this one). I imagine they used estimated values in steps of 10 degrees.

You can see my detailed workings using Lidar for one building in Merthyr Tydfil (the imagery was off vertical when I mapped it):


The solar panels are located on a gabled roof which is approximately 54 m across and 1.6 m high with works out as atan(1.6/27)=>3.4 degrees.

I suspect in all these cases the panels are laid flush with the roof, BUT there are other cases, particularly on flat roofs where panels are mounted on a frame at an angle to the roof (support=frame). In these cases I presume the panels are angled at the optimum value for the latitude.

solar panels tilted on a frame

Also it is not infrequent on flat roofs to see panels mounted in a sawtooth arrangement with alternate rows of panels angled (usually) to E & W. This latter arrangement presumably allows more panels to fitted into a smaller roof area. These have usually been recorded with a note=*

Zigzag solar panel arrangement