This page explains how the guides on PastView Maps are researched, so you can judge how far to rely on them.
1. Choose public test locations
We test with well-known public places such as landmarks, parks and public buildings. We do not use private homes as examples.
2. Run the same search in each tool
For every tool in a guide we repeat the same steps from the official interface, using the same location, and write down what we see: the oldest result available, the coverage, whether the service is free, and any sign-in or fee that appears.
3. Record the date
Each guide shows a “Last tested” date. Results can change when an agency adds new scans or redesigns a website, so a guide is only a snapshot of that date. We update the date only when we have actually repeated the test.
4. Show only what we are allowed to show
- Images created by the U.S. Geological Survey are in the public domain; we credit the source.
- Images under open licences such as CC BY are shown with the required attribution and licence.
- For services whose imagery is restricted or sold (for example Google Earth, commercial archives or national aerial photo collections), we describe where to click and what the result says, and link to the source instead of republishing the images.
5. State the limits
Coverage differs by place and year. A tool that finds a 1950s photo for one landmark may find nothing for another. Where we could not confirm something, the guide says so.
Spotted a mistake? See Corrections.