How do I interpret a confidence assessment?
 
All habitat maps are predictive to some degree and can only really be tested through practical use. Maps attract more confidence if they have been inspected and approved by external experts, particularly those with local knowledge of the area depicted on the map. Maps may have been used and found to predict accurately based on independent validation. They might, more generally, have been used by stakeholders and found to be acceptable particularly where they have stood the test of time.
 
While maps may not score highly on any measure of confidence this does not necessarily mean that they have little use in certain applications. Indeed, such a map may turn out to match well to a completely independent data source and this can lead us to revise our opinion of a map. For example, the habitat map below was derived from data collected between 1994 and 1996, on different vessels, using only AGDS, with varied track spacing (often more than 500m apart), with an uneven spread of ground truth data collected using only towed video. Using the scoring system, the map attains an overall score of 51%, which is quite a low confidence score.
 
 
GMHM5-20_Life-forms
 
A basic habitat map of the Sussex coast, UK derived from AGDS using a coarse track spacing (>500m);
it has a relatively low accuracy (51%).
 
 
The second map (below) has an overlay of fisheries sightings data (coded according to fishing method). These data, collected between 2004 and 2006 also have their limitations as to accuracy. However, the correspondence between fishing activity and habitat distribution is readily apparent.
GMHM5-21_Fishing_method
 
A habitat map overlain with known locations of fishing activity; despite the maps
relatively low accuracy, the fishing method broadly match the predicted habitat
thus affording greater confidence to the map.
 
 
Thus, maps may prove to be useful even if they do not attract high confidence initially. It also follows that while the survey strategy might not have been ideal given the constraints at the time, it might still produce maps of some value.

All material variously copyrighted by MESH project partners 2004-2010

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