The base map tiles and the mapping library come from the internet; the address data travels in this folder. If you are offline the points and the lookup still work — only the background image will be blank.
What this is measured against, and when it changes
The insurance class, the hydrant credit and the five-road-mile test all come from the 2022 ISO grading — the most recent survey on file, and the one still in force. The distances are measured on the county’s own street centreline network as of September 2026. None of it is frozen. Every layer on this map is a data file sitting in the folder beside this page: when a newer ISO grading is published, when the City’s travel-time records arrive, or when any of the outstanding public-records requests are answered, the file is replaced and the map is rebuilt from it. That is the point of publishing the data rather than a picture of it. If a figure here is wrong, write and it will be corrected with the source named.