Map Types and Scales
Use this page when you want to understand the difference between map layers in OMN4 and why one map may show more detail, cover a wider area, or need more storage than another.
What a map type means
A map type is a map layer.
Typical examples include:
- detailed topographic mapping such as OS 1:25,000
- broader topographic mapping such as OS 1:50,000
- imagery where available
- height data
- downloadable search data for supported areas
The map types available to you depend on your subscription and the area you are looking at.
What a scale means
The scale tells you how much detail a map is showing.
In everyday use:
- 1:25,000 usually shows more detail
- 1:50,000 usually shows less detail but covers a wider area
That means a more detailed map can be better for close route work, but it may also need more storage if you download it for offline use.
A simple way to think about common scales
| Scale | What it usually means in practice |
|---|---|
| 1:25,000 | More detail, more labels and features, often a larger offline download for the same ground area |
| 1:50,000 | Less detail, broader view, often a smaller offline download for the same ground area |
| Imagery | Photo-style view rather than a drawn map |
| Height data | Elevation-related data rather than a normal paper-style map |
Not every area offers every map type.
Why some map types appear in different places
Some map types can be both:
- viewed directly on the map
- downloaded in Map Management
Others are mainly managed through Map Management.
This is why the map you are currently looking at is not always the same as the map data you are downloading.
For example, some download-only data types are useful to have on the device even though OMN4 does not treat them like a normal main viewing map.
What affects availability
Whether you see a map type can depend on:
- your subscription
- the area or country you are in
- whether the map is meant for normal viewing, downloading, or both
- whether the map data is stored on your device already
If a map is not listed where you expected it, first check the area, then check Map Management.
What affects download size
Download size is not only about scale.
It can also depend on:
- how much area you are saving
- whether the map is already partly on your device
- whether OMN4 is updating older downloaded data
- whether some stored data is shared with other nearby areas
This is why two map types covering the same place can use very different amounts of storage.
Good rules of thumb
- Choose the map type first for the detail you want.
- Choose the area second for how much coverage you need.
- Use Map Management when you want to compare offline sizes and save data on the device.
- Expect detailed maps to need more storage than broader-scale maps.