For detection, a common way to determine if one object proposal was right is Intersection over Union (IoU, IU). This takes the set $A$ of proposed object pixels and the set of true object pixels $B$ and calculates:$$IoU(A, B) = \frac{A \cap B}{A \cup B}$$Commonly, IoU > 0.5 means that it was a hit, otherwise it was a fail. For each class, one can calculate theTrue Positive ($TP(c)$): a proposal was made for class $c$ and there actually was an object of class $c$False Positive ($FP(c)$): a proposal was made for class $c$, but there is no object of class $c$Average Precision for class $c$: $\frac{\#TP(c)}{\#TP(c) + \#FP(c)}$The mAP (mean average precision) = $\frac{1}{|classes|}\sum_{c \in classes} \frac{\#TP(c)}{\#TP(c) + \#FP(c)}$If one wants better proposals, one does increase the IoU from 0.5 to a higher value (up to 1.0 which would be perfect). One can denote this with mAP@p, where $p \in (0, 1)$ is the IoU.But what does mAP@[.5:.95] (as found in this paper) mean?
What does the notation mAP@[.5:.95] mean?
computer vision
mAP@[.5:.95](someone denoted mAP@[.5,.95]) means average mAP over different IoU thresholds, from 0.5 to 0.95, step 0.05 (0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95).There is  an associated MS COCO challenge with a new evaluation  metric, that averages mAP over different IoU thresholds,  from 0.5 to 0.95 (written as 0.5:0.95). [Ref]We evaluate the  mAP averaged for IoU  [0.5 : 0.05 : 0.95] (COCOs  standard metric, simply denoted as mAP@[.5, .95])  and mAP@0.5 (PASCAL VOCs metric). [Ref]To evaluate our final detections, we use the official  COCO API [20], which measures mAP averaged over IOU  thresholds in [0.5 : 0.05 : 0.95], amongst other metrics. [Ref]BTW, the source code of coco shows exactly what mAP@[.5:.95] is doing:self.iouThrs = np.linspace(.5, 0.95, np.round((0.95 - .5) / .05) + 1, endpoint=True)Referenceshttps://github.com/pdollar/cocohttp://mscoco.org/https://www.cs.cornell.edu/~sbell/pdf/cvpr2016-ion-bell.pdfhttps://arxiv.org/pdf/1506.01497.pdfhttps://arxiv.org/pdf/1611.10012.pdf