All of the layers on NABIS will have limits to their accuracy. Accuracy is specific to an individual layer. The level of accuracy depends on:
- How much is known about the topic
- How much of this knowledge is available on databases
- How much of this knowledge is freely available (no Copyright or Intellectual property constraints)
- How much time/resources were available to collect the information for NABIS
- How the information was collected
- How the information is displayed on NABIS
A coloured triangle lets you know that there is an accuracy issue in the layer or there is relevant information that a user of the layer needs to know. The higher the number, the more significant the issue. If a data layer doesn't have any special warnings, it doesn't mean that it is 100% accurate. The 'accuracy' tab in the Details/metadata, the lineage and sometimes the attribute data all have information relating to accuracy and issues of concern.
It is very important that you read the layer Details/metadata, lineage and attribute data to determine if the layer is appropriate for your use.
- level
: Low level alert: There are minor errors, omissions or inaccuracies in this layer
- level
: Medium level alert: There are errors, omissions or inaccuracies in this layer
- level
: High level alert: There are significant errors, omissions or inaccuracies in this layer
Accuracy alert symbols appear in the legend for a data layer. This is an indication that you should check the layer Details/metadata (Eg Bathymetry). 
The 'Accuracy' page of the Details/metadata has information on any accuracy issues. (Eg Bathymetry) 