Missing and misplaced wind turbines Clocaenog forest North Wales

1. Log into OpenStreetMap
2. Zoom to the area in question
3. Click "Edit"
4. Follow the tutorial
5. Make your edits
6. Save

Best practice is to ask the original mapper via a Changeset Discussion,as this will likely reveal what sources they used & how reliable the data might be.

Alternatively you can add notes on the OSM website for the missing & incorrectly located turbines, or you can edit & adjust them yourself (as long as you dont use copyright Ordance Survey data, and in particular anything related to MasterMap)

Jex Nicholson seems to have done much of the mapping (e.g., https://www.openstreetmap.org/changeset/70349292#map=13/53.0835/-3.4825), but although the changeset says Bing Imagery used he may have used other less detailed sources as only some turbines are visible on any current imagery in the OSM editors (ESRI & Maxar Standard. A lot of renewable energy data is entered fairly roughly at first (often because detailed imagery is not available), so we're always open to improving it. As a first cut I have added one turbine & slightly adjusted the position of others, but I dont see any which are 130 m out.

I'm presuming you are encountering these in the field, but one remote possibility if this is GIS-based is use of a suboptimal transform between WGS84 and OSGB National Grid.

It is difficult to map them if access is restricted or aerial is unavailable. As SK53 suggested approximate positioning is still helpful, especially for rough navigation. This is a method i used a while ago. https://help.openstreetmap.org/questions/50366/mapping-without-access-or-new-enough-bing