Imagery is a photograph, not a measurement of today
Satellite and aerial map imagery is a snapshot taken at some point in the past, and each area is refreshed on its own schedule. Dense urban areas tend to be updated more often. Rural and low-traffic areas can go much longer between updates, and the image on screen may predate recent changes by a wide margin. The map does not always tell you which date you are looking at.
For a solar project, that gap matters because the things that decide a design are exactly the things that change: a new roof, an added building, an extension, rooftop equipment, a carport, a fence line, or trees that have grown since the picture was taken.
What outdated imagery gets wrong
- Roof condition and layers. A roof may have been replaced, overlaid or patched since the photo, which changes both the usable area and the structural picture.
- Obstructions. New rooftop units, vents, antennas or skylights may not appear.
- Shading. Trees grow, and new buildings or structures appear nearby. A shading estimate from an old image can understate the problem.
- The building itself. Additions, demolished sections and new outbuildings can all change what should be surveyed.
- Ground conditions. On ground-mount sites, grading, drainage, new roads and clearing may have changed the lot.
None of these is dramatic on its own. The risk is that they accumulate silently, and the first person to notice is often the installer standing on the roof.
Why rural sites are exposed
Rural properties often include several buildings, long conduit runs, large open areas and equipment that has been added over time without updated drawings. At the same time, they are the properties where imagery is most likely to be old and where an unnecessary extra trip costs the most. The combination makes verification at the first visit worth more, not less.
How to handle imagery responsibly
Check the date
Where the tool shows an imagery date, read it. Compare more than one source if you can. If two sources disagree, assume neither is current.
Ask the owner what has changed
A short call with the owner or facility manager is cheap and often decisive. Ask about roof work, new buildings, equipment added or removed, and trees cut or planted.
Treat the layout as preliminary
A concept layout drawn from old imagery is fine as a conversation starter. Label it preliminary and keep it away from structural and electrical decisions.
Confirm on site
The survey is where the current condition is recorded with photographs and measurements. For a larger property, aerial capture on the day can document the roof and surroundings as they are now, which the note on drone versus manual survey explains. For the broader trade-off between remote and on-site work, see remote versus onsite solar site surveys.
What the survey should record about change
A good survey does more than measure. It notes where reality differs from the information the team started with: the extra building that was not on the map, the roof layer that is not in the drawings, the tree that now overhangs the south edge. Those notes let the engineer correct the model early, and they give the owner a clear record of what was found.
A short checklist for projects with old imagery
- Note the imagery date from each source you used, and record that it may be out of date.
- Ask the owner for a list of changes to the roof, buildings and equipment since the last few years.
- Flag every dimension taken from imagery as unverified until the survey confirms it.
- Ask the crew to photograph all four sides of each building and the approach roads, so changes are documented.
- Update the layout only after the survey, and keep the earlier version for comparison.
Where Solar Survey AI fits
Solar Survey AI sends a technician to the property for the commercial on-site survey: the roof, the structure and the electrical room recorded in one visit, with turnaround confirmed when we scope the job. If your project sits in an area where the imagery is old, tell us when you book and we will scope the visit to confirm what the photographs cannot.