A drive-through pallet dimensioner (also called a portal scanner or DTPS — Drive-Through Pallet Scanner) is a fixed measurement system installed as a structural arch or portal that forklifts or pallet jacks drive through during normal material movement. As the vehicle and its freight pass through the portal, sensors capture the full three-dimensional measurements of the pallet load without requiring the operator to stop, position the freight, or interact with the system in any way.
The drive-through configuration makes it fundamentally different from kiosk-style dimensioners, where the operator must stop the forklift, position the pallet within the measurement zone, and initiate the scan. A portal scanner is passive from the operator's perspective: measurement happens automatically as part of the existing traffic flow.
A drive-through pallet dimensioner uses a combination of sensors mounted on the portal arch to capture measurements as the freight passes through:
Line-scan lasers project planes of light across the portal opening from multiple angles. As the pallet load moves through the portal, the laser planes intersect the freight surfaces at different heights and positions. Cameras observe how the laser lines deform against the freight surface, and this deformation data is processed to reconstruct the three-dimensional shape of the load.
Photocells on each side of the portal detect when a load enters and exits the measurement zone. The forklift's travel speed (either measured by doppler sensors or estimated from portal transit time) is used to calculate the length of the load. For higher accuracy, some portal systems use ground-embedded speed measurement to track the precise travel velocity of the forklift throughout the portal transit.
The complete measurement cycle — from the moment the leading edge of the load enters the portal to the moment the trailing edge exits — takes between 1 and 3 seconds depending on the portal width, forklift speed, and pallet load size. The measurement result is available within 500ms of portal exit.
A typical drive-through pallet dimensioner captures:
Drive-through portal systems require permanent structural installation. Key requirements include:
Forklifts that unload trucks and move pallets to the staging area naturally pass through a portal positioned at the dock door or at the entrance to the receiving lane. Every inbound pallet is automatically measured as it enters the facility. Verified dimensions are written to the receiving record in the WMS without any additional operator steps.
Pallets staged for outbound carrier pickup are dimensioned as the forklift moves them to the outbound staging area. Verified dimensions are applied to the BOL and carrier pickup request before the carrier arrives, ensuring declared dimensions match measured dimensions and preventing re-weigh adjustments.
In cross-dock terminals where freight arrives and departs with minimal storage time, portal dimensioners installed at each dock door capture both inbound and outbound dimensions automatically, supporting freight class billing and load planning without slowing the cross-dock workflow.
When pallets move from receiving to putaway storage, portal measurement provides verified dimensions for WMS slotting decisions. The WMS uses measured height and volume to assign the correct storage location, reducing slot rejection rates and improving storage density.
Drive-through portal dimensioners typically achieve measurement accuracy of +/-5mm on each dimension for standard rectangular pallet loads. Irregular loads with significant protrusions, curved surfaces, or hanging elements may have lower effective accuracy. Calibration requirements include:
No. The drive-through portal measures automatically as the forklift passes through at normal speed. There is no button to press, no positioning required, and no interaction needed from the operator. The measurement is captured passively during normal material movement.
Most portal systems are designed for forklift transit speeds of 2-8 km/h (the typical speed range for loaded forklifts in a warehouse). Some high-accuracy systems require the forklift to stay below 5 km/h for optimal measurement accuracy. Speed limits for the portal area are typically posted and enforced through normal traffic management.
Yes, within limits. Stretch-wrapped pallets are handled well by all portal systems. Irregularly shaped loads (machinery, non-rectangular equipment) are measured to their maximum bounding box dimensions. Loads covered by tarps or shrouds are measured to the outer surface of the covering, which is correct for freight billing.
A portal scanner measures freight during normal forklift movement, requiring no operator interaction. A kiosk dimensioner requires the operator to stop the forklift, position the pallet within the measurement zone, and initiate the scan. Portal scanners have higher throughput but require permanent installation; kiosks are more flexible and lower cost but slower.