Historical Satellite Imagery: Compare Old Images by Year

Where the old satellite images come from

The satellite basemap in web maps is not fixed. Esri updates its World Imagery map several times a year, and each update replaces the imagery for part of the world. Since 2014 Esri has kept every published release in an archive called World Imagery Wayback. This tool uses that archive: it opens historical satellite imagery for a location and lets you compare two dates on the same screen.

Comparing satellite images over time is a practical way to see how a neighbourhood was built up, when a road or a dam was constructed, how forests and farmland changed, or how a shoreline moved. While you browse the old satellite map, you can also see when each image was actually captured.

How to use it

1. Type an address, district or town in the search box, or drag the map to the place you want to examine. If you know the coordinates, enter them as "latitude, longitude".
2. When the map stops moving, the tool finds the Wayback releases in which the imagery actually changed in the tile at the map center. By default the oldest release is selected as A and the newest as B.
3. Change dates A and B from the drop-down lists or with the date buttons in the timeline. A date you click in the timeline goes to A first and then to B.
4. In Swipe view, drag the handle in the middle or move it with the arrow keys. In Side by Side view the two maps move together; on a phone they are stacked.
5. The results show the capture date, source, resolution and positional accuracy of both images. Click a point on the map to see the same details for that point.
6. "Save PNG" saves the comparison on your screen with the dates and attribution. "Copy Link" copies an address that contains the location and the two selected dates.

Release date and capture date are not the same

The dates in the list are the dates on which Esri published that release of the map. The date the image was taken from a satellite or an aircraft is usually earlier, sometimes by a few months, sometimes by several years. For that reason the tool queries Esri's metadata service for each release and shows the capture date, provider, pixel resolution and positional accuracy of the image at the map center. When you draw conclusions, rely on the capture date, not the release date.

Data and method

The release list is read from the official configuration file (waybackconfig.json) that Esri's own Wayback app uses. Tiles come from Esri's Wayback WMTS service. The list of local changes follows the approach of the Wayback app: starting from the newest release, the tile map (tilemap) is queried at each step to learn which release the tile actually comes from, and the search moves on to the release before it. Consecutive tiles of the same size are compared byte by byte to remove duplicates. This logic follows Esri's open source wayback-core library (Apache-2.0 license).

The map runs on Leaflet 1.9.4 (BSD-2-Clause license) and the icons come from Lucide (ISC license). Place search uses OpenStreetMap Nominatim with at most one request per second. No API key is used for the Esri services, which are publicly available. All processing happens in your browser.

Limits of use

• Rights: The imagery belongs to Esri and its providers (Vantor, formerly Maxar; Earthstar Geographics and others). Use is subject to Esri's master license agreement and terms of use. Keep the attribution visible in any image you save. The tool does not download tiles in bulk for offline use.
• Not official evidence: The images are for information only. Land registry, planning and court matters rely on official records, certified surveys and expert assessment.
• Coverage: In rural areas the imagery may not be updated for years. Finding only two or three different images for a place is normal.
• Position and resolution: Images from different dates may be offset by a few metres, and resolution varies by provider from about 0.3 m to 15 m. Building corners may not line up exactly.
• Map center: The change scan is based on the tile at the map center. The edges of the screen may show imagery from other dates; move the center and rescan if needed.

For organisations

Monitoring unpermitted construction or land use change across a municipality or a large asset base calls for systematic, repeated analysis rather than comparing images one by one. If your organisation needs such a workflow built on ArcGIS, learn more about Rodosto Teknoloji or get in touch with us.