Checks

Seven checks before any model looks.

These run on the photos and their records, with no AI involved. Each can be switched off in Settings on the home page. Here is what each one does, and what it can miss.

Same photo

Both dates show one image at this zoom

The archive stores photos per zoom level. Two different dates can still serve the identical photo at the zoom you are looking at, usually below zoom 16. The check asks the archive which release really holds the photo in view for each date.

Can miss: It checks the centre of the view. A photo that differs only at the edges can pass as different.

Resolution mismatch

A sharper photo can make things look new

When one photo is 100 cm per pixel and the other 30 cm, the sharp one shows cars, rubble and small buildings the other simply cannot. The check compares the resolution in Esri's records and warns from a factor 1.5.

Can miss: Records give the source resolution. Haze or blur in the photo itself is not measured.

Time gap

How far apart the two photos were taken

Shows the months or years between the capture dates, and warns above five years: over a long gap a place can be damaged and rebuilt, and the photos only show the end state.

Can miss: Needs both capture dates. Without them it stays silent.

Season

Leaves, snow and shadows differ by month

A photo from May and one from January differ in trees, fields, snow and shadow length. The check warns when the photos are three or more months apart in the calendar year.

Can miss: It does not know the local climate. A three-month gap in the tropics matters less than in Ukraine.

Unknown date

A photo without a capture record

Some photos have no capture record at Esri. Their date cannot be verified, so any change you see cannot be pinned to a moment.

Can miss: A record can exist and still be wrong. It is Esri's metadata, not the satellite operator's.

Zoom range

Dated photos live at zoom 16 to 18

The dated high-resolution photos are served at zoom 16 to 18. Further out both dates show the same coarse mosaic, further in there may be no archive photo at all. The comparison view keeps you inside that range.

Can miss: Some places have dated photos at other zooms too. The check is a rule of thumb from measurements, not a guarantee.

What stands here

Hospitals, schools, places of worship in view

Asks OpenStreetMap which hospitals, clinics, schools, universities, places of worship and named historic sites lie inside the view, so you know what the buildings in the photo are before you describe them.

Can miss: OpenStreetMap is edited by volunteers. A site can be missing, mislabelled, or already destroyed.

Then the AI

After these checks, the AI reads both photos cell by cell. Every change it reports must describe what is visible in both photos, or it is thrown away. How that works.