Review 04 · Live Intelligence
Undersea.
701 submarine cables from TeleGeography's public dataset, drawn by the page's own code and still working with the network gone. The price of owning the whole chain is that the data is a month old.
- Tested 27 September 2026, 20:10–20:13 UTC
- Where the work happens data shipped with the page
- Against TeleGeography Submarine Cable Map, Submarine Networks, Infrapedia
1What it is, and who it is for
Undersea is a map of the physical internet: 701 submarine cable systems and 1,921 landing stations, drawn on the page's canvas with pan, pinch and wheel zoom. You can search by cable or landing town, browse a ledger searchable by name and owner, and open a card for any cable with its stated length, owners, landings and ready-for-service year. Systems not yet in service are dashed.
It is for students, journalists and the network-curious who want to see which cables land where and who owns them, including on a train with no signal.
2How it works
After load, nothing travels. undersea/assets/js/undersea-data.js, 529,438 bytes, is built by tools/mkundersea.py from source files that ship in the same folder (the cable list, the landing points, a Natural Earth coastline extract and 704 cable detail files), so anyone can rebuild it (undersea.js 1–13; index.html 536–544).
Sea routes are delta-encoded at a twentieth of a degree and coastlines at a tenth; the page decodes them, then releases the global so the memory is returned (undersea.js 9–13, 24–60). The projection is the page's own equirectangular renderer, with no tile server or map library. Search matches cable and station names (447–453), the ledger also matches owners (494–500), and a MutationObserver redraws the chart when you switch between paper and dark (17, 574).
Lengths are the operators' own figures. Where a system publishes none, the card shows a dash rather than an estimate.
3The test
We fetched the page and its data pack from the local 537 copy, parsed the pack ourselves to compare our counts with the page's, then searched the engine for network calls.
Parsed the pack.
701 cables. 1,922 landing records, 1,921 of them referenced by a cable; the one left over is Little Saint James, US Virgin Islands, as the page's note says. 628 cables with a stated length, 68 with a ready-for-service year after 2026, 127 coastline polygons, dataset dated 28 August 2026.
Loaded the page (at 20:10:48) and the data pack.
Page HTTP 200, 47,369 bytes; pack HTTP 200, 529,438 bytes (our local server sent it uncompressed); undersea.js 26,083 bytes.
Searched undersea.js for fetch and XMLHttpRequest.
No network calls. The only two matches for 'fetch' are the dataset's FETCHED date variable, at lines 28 and 588.
4Against the field
Each rival was read on its own pages on the test day. Pencil marks what it does better; red, where Undersea goes further.
TeleGeography Submarine Cable Map
submarinecablemap.com · checked 27 September 2026, 20:14 UTC
The source of Undersea's data: TeleGeography's interactive cable map, updated on a rolling basis, alongside an annual printed wall map whose 2026 edition depicts 694 cable systems and 1,893 landing stations, with fibre pairs and lit and potential capacity on major routes.
In pencil
- It is the source, and it is kept current; Undersea's pack is dated 28 August 2026.
- The printed 2026 edition adds capacity analysis (fibre pairs, lit and potential capacity) that Undersea does not carry.
In red
- Works with no network at all once loaded, and makes no requests while you explore.index.html 541–544
- Explains in plain words what a drawn route is and is not, and why one of 702 systems is missing.index.html 554–571
- Ships its build script and raw sources, so the chart can be rebuilt and audited.tools/mkundersea.py
Submarine Networks
submarinenetworks.com · checked 27 September 2026, 20:25 UTC
An industry hub: news and analysis on submarine cables, a cable-system database organised by region, a landing-station directory by continent and country, and articles submitted by readers.
In pencil
- News and industry analysis around each system, which Undersea does not attempt.
- Editorial detail for each system and each landing station.
In red
- One zoomable chart with every system and landing drawn together, searchable by cable, town or owner.undersea.js 272–320, 447–453, 494–500
- Only what the dataset states: a missing length shows as a dash.index.html 560–563
Infrapedia
infrapedia.com · checked 27 September 2026, 20:14 UTC
Describes itself as 'the world's largest network and datacenter infrastructure atlas'. That tagline was all our fetch returned, so we claim nothing further about it.
In pencil
- By its own description it covers data centres as well as networks; Undersea covers submarine cables only.
In red
- Undersea keeps working offline once loaded. We did not verify how Infrapedia's map loads, so this is a statement about Undersea only.index.html 541–544
5Where it falls short
- A snapshot. The data is dated 28 August 2026 and changes only when the pack is rebuilt, while TeleGeography keeps its own map current.
- Corridors, not routes. Lines are cartographic, and there is no capacity, fibre-pair or utilisation data.
- Half a megabyte first. The pack must load before anything is drawn, which is heavy on a slow phone connection.
- Cables only. No terrestrial networks, data centres or exchange points.
- A non-commercial licence. The dataset's CC BY-NC-SA 4.0 terms limit commercial reuse of what is shown.
6The verdict
Undersea is a model of a self-contained chart (sourced, rebuildable, private, and honest about what a line on a map means), provided a month-old picture of the seabed is recent enough for you.
- In red ink
- No tiles, no requests after load, build script and sources shipped, and counts that match the data exactly.
- In pencil
- For the current map and capacity figures, TeleGeography; for news and analysis, Submarine Networks.