41% of Global AIS Positions Come From "Other." That Category Has No Informative Classification. It Also Has the Most Positions.

24.8 million vessel position records in 28 days. The highest-volume category by position count is not bulk carriers. It is not tankers. It is "other" — the catch-all for vessels that don't fit a recognized type. 41.3% of the ocean's visible traffic is unclassified.

The Setup

The last 28 days generated 24.8 million AIS position records across all active H3 cells in the global coverage area. That volume spreads across 13 vessel type categories tracked in the density index.

Bulk carriers have the widest geographic footprint: 354,218 distinct H3 cells in 28 days. Tankers are third-largest by position count at 4.4 million positions across 237,357 cells. Containers and general cargo together account for another 2.3 million positions.

The largest single category by raw position count is "other": 10.25 million positions, 241,917 cells, 41.3% of all AIS traffic in the window.

"Other" is not a vessel type. It is a classification placeholder — the catch-all for vessels whose AIS type code does not map to a recognized commercial category. Service vessels, offshore support platforms, vessels with misconfigured transponders, and unregistered type codes all land in "other." The category generates more position pings than any commercial vessel class while carrying the least identification value of any entry in the index.

The Chain

The concentration numbers first. Of the roughly 529,820 distinct H3 cells that received any vessel position in the last 28 days, the top 10% of cells — 52,982 cells — absorbed 93.3% of all 24.8 million positions. The bottom 10% of cells (52,981 cells) each received exactly one position across the entire four-week period. Most of the ocean generates no useful traffic intelligence.

Within that concentration, the "other" category produces the densest clusters. The single highest-position cell in the 28-day window recorded 87,230 positions from 186 unique "other" vessels — roughly 3,115 pings per vessel per month. These are not transiting vessels. They are stationary or slow-moving: offshore support, anchorage-bound vessels, or platforms in slow holding patterns generating high-frequency AIS bursts.

For comparison, the densest bulk carrier cell in the same window had 45,261 positions from just 3 unique vessels — an extended anchorage dwell by a small number of large vessels. That is a different archetype: few vessels, long duration. The "other" clusters are many vessels in dense congregations.

The Implication

41.3% of global AIS volume is unclassifiable at the type level. This is not a marginal data quality problem affecting a small corner of the dataset. It affects the plurality of traffic. Risk models built on vessel-type assumptions — tankers near oil terminals, bulk carriers in grain corridors, containers at box ports — operate on 58.7% of the position record. The "other" 41.3% is opaque to type-based routing and anomaly detection.

The concentration finding compounds this. 93.3% of positions land in 10% of cells. The sparse 90% of ocean cells generate essentially no useful intelligence. Analytical coverage of cells outside the top decile has near-zero marginal return. The useful maritime signal is geographically concentrated enough that blanket global coverage adds little over focused coverage of the 52,982 high-density cells — but type-classification problems in those cells affect the quality of all inference drawn from them.

What to Watch

• Whether "other" category share of total positions is growing or shrinking over 12 months. If it is growing, AIS classification quality is declining as the fleet expands faster than type-code registration discipline.
• What share of the top-decile H3 cells overlap with known dark event hotspots. If "other" category dense clusters overlap with Gulf anchorage rings or known transfer zones, there is a compound opacity problem: unclassified type plus dark event proximity means neither vessel identity nor vessel activity is resolvable.
• Vessel-type reclassification rates in the identity graph — whether untyped vessels are eventually resolved via ownership or flag lookup, or remain permanently in the "other" bucket throughout their tracked lifespan.

Limitations

The "other" category includes vessels that legitimately have no standard AIS type: some service and offshore support classes do not map cleanly to the IMO type code taxonomy. The 10.25 million "other" positions are not 10.25 million unclassified risk events — many are routine service vessel transits with no evasion concern. The H3 concentration figures reflect position density, not vessel-hour or movement density; a vessel sitting in one cell for four weeks with high-frequency pinging will outscore a vessel transiting across 40 cells. The 28-day window is too short to identify seasonal patterns in vessel type distribution.

Data as of July 13, 2026. Source: Axiom Overwatch vessel_density_h3_weekly, June 15 – July 13, 2026. n=24.8M positions across 529,820 active H3 cells.