Annotation consolidation
An annotation is the result of a single worker's labeling task. Annotation consolidation combines the annotations of two or more workers into a single label for your data objects. A label, which is assigned to each object in the dataset, is a probabilistic estimate of what the true label should be. Each object in the dataset typically has multiple annotations, but only one label or set of labels.
You decide how many workers annotate each object in your dataset. Using
more workers can increase the accuracy of your labels, but also increases the cost of
labeling. To learn more about Ground Truth pricing, see Amazon SageMaker Ground Truth pricing
If you use the Amazon SageMaker AI console to create a labeling job, the following are the defaults for the number of workers who can annotate objects:
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Text classification—3 workers
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Image classification—3 workers
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Bounding boxes—5 workers
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Semantic segmentation—3 workers
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Named entity recognition—3 workers
When you use the CreateLabelingJob operation, you set the number of workers to
annotate each data object with the NumberOfHumanWorkersPerDataObject
parameter. You can override the default number of workers that annotate a data object
using the console or the CreateLabelingJob operation.
Ground Truth provides an annotation consolidation function for each of its predefined labeling tasks: bounding box, image classification, name entity recognition, semantic segmentation, and text classification. These are the functions:
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Multi-class annotation consolidation for image and text classification uses a variant of the Expectation Maximization
approach to annotations. It estimates parameters for each worker and uses Bayesian inference to estimate the true class based on the class annotations from individual workers. -
Bounding box annotation consolidates bounding boxes from multiple workers. This function finds the most similar boxes from different workers based on the Jaccard index
, or intersection over union, of the boxes and averages them. -
Semantic segmentation annotation consolidation treats each pixel in a single image as a multi-class classification. This function treats the pixel annotations from workers as "votes," with more information from surrounding pixels incorporated by applying a smoothing function to the image.
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Named entity recognition clusters text selections by Jaccard similarity and calculates selection boundaries based on the mode, or the median if the mode isn't clear. The label resolves to the most assigned entity label in the cluster, breaking ties by random selection.
You can use other algorithms to consolidate annotations. For information, see Annotation consolidation function creation.
