Symptom-First Title: What does "OCM format" mean and when do you encounter it?

Symptoms / Triggers:

1. You see the term "OCM format" in documentation or when integrating HERE Map Content.
2. You encounter a reference to compact map layers or optimized transfer of map data.
3. You need to work with map layers for client-side use in applications or tools.

Quick Answer: The Optimized Client Map (OCM) format is a compact and efficient map data format used by HERE for fast storage, decoding, and client-side use. It organizes map layers and tiles to reduce download and caching overhead.

Step-by-Step Explanation:

1. Understand the packaging structure: OCM groups layers to minimize downloads and transfers. A catalog includes a configuration layer and an index layer to manage bundle roots for groups.
2. Examine the tile organization: Each layer group is stored as partitioned tiles (500 KB bundles) with encoded tile data in Protobuf (Protocol Buffers) schemas.
3. Use the HEREtile Tiling Scheme: OCM uses quadtiles to divide the world recursively. Tile coordinates are calculated using WGS84 degrees converted to Morton code (quadkeys), optimized for fast indexing and geographic referencing.
4. Coordinate precision: Geometry is encoded using relative integer coordinates for compact storage. For level 14 tiles (standard in HERE systems), the world_coordinate_bits is typically 25, enabling ~1.2 meter precision.
5. Implement client access: For C++ applications, use the OCM Access Manager to handle tile downloading and caching seamlessly.

Applies To:

HERE Map Content users (developers working with map layers and Protobuf data).
Applications needing efficient map tile handling (e.g., navigation systems, offline maps).
* Projects utilizing HEREtile Tiling Scheme and compact map data for client-side rendering.

Resource

Maps and services: https://docs.here.com/here-sdk/docs/android-customization-catalogs

Customer-Searchable Tags:

OCM, Optimized Client Map, map format, HEREtile, tile, Quadkey, WGS84, Protobuf