Container tracking for fresh produce importers

A reefer of Chilean cherries left Valparaíso six weeks ago, bound for Rotterdam, and it is sold. Every importer watching that box is really asking one of three questions: will it arrive when I sold it for, is the fruit still going to be worth what I paid, and do I need to do something today. A tracking page that answers “in transit” answers none of them.

This guide covers what container tracking data actually is, where it comes from, why the position on the map is frequently wrong, and which events are worth building a process around.

What “tracking” is made of #

A container’s journey is reported through three different systems that do not agree with each other.

Carrier milestones come from the shipping line. Gate-in, loaded on vessel, vessel departed, transshipped, discharged, gate-out, empty returned. They are authoritative — the line is the party that did the thing — but they are published in batches, sometimes hours after the event, and occasionally out of order.

AIS vessel positions come from the ship, not the container. Vessels broadcast their position over AIS, terrestrial receivers and satellites pick it up, and that is what draws the line on the map. It tells you where the vessel is, which is only where your container is if your container is still on that vessel.

Terminal and port data covers what happens between discharge and gate-out: the part of the journey where demurrage accrues, and the part with the worst data coverage.

Most tracking products blend all three and present the result as one confident-looking dot. Understanding which source a given fact came from is what tells you how much to trust it.

Why the position on the map is often wrong #

The dot is interpolated more often than importers realise.

A vessel mid-ocean may go hours between AIS fixes, especially outside satellite coverage. Rather than show a stale position or nothing at all, most systems draw a straight line between the last known fix and the expected next waypoint and place the vessel somewhere along it, moving at its average speed. That dot is a guess with a plausible shape.

It is usually a good guess. It stops being one when the vessel does something the interpolation cannot know about: slow steaming to save fuel, waiting at anchor for a berth, diverting around weather, or being rerouted. Then the interpolated dot keeps gliding toward the destination on schedule while the actual vessel sits still.

The practical consequence: a dot that is moving smoothly is not evidence that the vessel is moving. Treat the timestamp of the last real fix as the fact and the position as an estimate. When the two are far apart, the ETA built on top of it is worth less than it looks.

The events actually worth watching #

Out of a dozen or more milestones, four change what you do:

Departure from origin. Confirms the container is on the water and on which vessel. Until this lands, everything downstream is a booking, not a shipment.

Transshipment. The container moves to a second vessel at a hub port — Algeciras, Singapore, Colón. This is the most common point at which a container and its ETA quietly part company — if it misses the connection it waits for the next one, which can be a week. It is also the point at which tracking a vessel stops telling you about your container.

Discharge at destination. Starts your free time. Not the ETA — discharge. Everything about avoiding demurrage depends on knowing this date as it happens rather than reconstructing it from an invoice later.

Gate-out. The container has left the terminal. Demurrage stops, detention starts.

What an ETA is worth #

An ETA is a forecast, and its quality decays with distance. Six weeks out it is a schedule; six days out it is an estimate; six hours out it is a fact. Importers who treat all three as the same number are the ones who book hauliers twice.

Why does my ETA keep changing? covers this in full. Two habits help. Watch the ETA’s movement rather than its value — a date that has slipped three times in a week will slip again, and that pattern is visible long before the final delay is. And separate the vessel’s ETA from your container’s: after a transshipment they are different numbers, and only one of them is about your fruit.

Tracking a reefer specifically #

A reefer container carries a fourth data stream that dry cargo does not: the temperature log from the refrigeration unit itself, recorded through the voyage and downloadable at the end.

This is the record that settles quality claims. A load that arrives soft is either a pre-shipment problem or a cold-chain problem, and the temperature log is the only thing that distinguishes them. It is worth pulling as a matter of routine rather than only when there is an argument, because by the time there is an argument the container has usually been returned.

Reefers also run on shorter free time at higher rates. The same delay that is an annoyance for dry cargo is a real cost here, which is why the discharge event matters more for a reefer than for anything else on the vessel.

Turning this into a process #

Tracking is only worth doing if something happens as a result. The shape that works:

1. Confirm the booking became a shipment. No departure event, no shipment.
2. Set the alert on transshipment, not on arrival. By arrival it is too late to do anything but pay.
3. Watch for silence. A container that has stopped producing events is the strongest signal in the data, and no tracking page shows it — an absent event does not render.
4. Act on discharge, not on ETA. Book the haulier and finalise clearance against the event, not the forecast.
5. Close the loop on the empty. Detention runs until the empty is returned, which is the step everyone considers somebody else’s job.

FAQ #

Why does my container’s position not match the shipping line’s website? #

Because the two are answering different questions from different sources. The line reports milestones it has recorded; a tracking map shows a vessel position derived from AIS, often interpolated between fixes. Neither is wrong — but the line’s milestone is a record of something that happened, and the map position may be an estimate of something happening now.

How accurate is a container ETA? #

Accurate enough to plan against within a few days of arrival, and not accurate enough to commit to six weeks out. The useful signal is not the date but its stability: an ETA that keeps moving is telling you something the number itself is not.

Can I track a container without the shipping line’s reference? #

Usually yes — a container number or a bill of lading number is enough to look up a shipment with most lines. What you get back varies: some lines publish a full milestone history, others only the current status.

What happens to tracking after a transshipment? #

The container changes vessel, so anything following the original vessel stops being about your cargo. This is the point where tracking quality most often degrades, and where a container most often loses a week without the ETA moving to match.

Does tracking tell me if the fruit is still good? #

No — but a reefer’s temperature log comes close. Tracking tells you where the container has been and how long it took; the temperature log tells you what the cargo experienced while it did. For a quality claim you need both.