The SENTINEL-3 user products are disseminated in Product Dissemination Units (PDU), in order to ease the online dissemination and data handling for the users.

The PDU is a portion of data and is defined per product type. Three kinds of PDU are defined for SENTINEL-3 products: "frame", "stripe" (see Figure 1) and "tile".

• A frame is identified by means of a fixed reference system based in along-track coordinates and along-orbit cycle coordinate. The along-track coordinate identifies the product frame start point with respect to a fixed orbit position (like the ANX). Each frame is stepped by a constant time interval along the orbit track. The along-orbit cycle coordinate identifies the relative orbit number within the orbit cycle.
• A stripe coincides either with the acquisition dump or with a defined acquisition time segment whose length may differ according to the instrument type (for example full orbit pole to pole, half orbit etc...). A special case of stripe is provided by the Vegetation like product (called VGT-P) where the stripe is mapped on a Plate Carrée geographical projection.
• Tiles are defined only for Vegetation-like 1 or 10 days synthesis products, VGT-S1 (SY_2_VG1) and VGT-S10 (SY_2_V10), provided on a Plate Carrée map projection. A tile corresponds to a geographical subset of the synthesis image as shown in Figure 2.

Figure 1: Example of PDUs for OLCI L1B products: stripe and frame concept

Figure 2: Example of PDUs for Vegetation-like products