Annotation with Polylines

Annotation with Polylines

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Annotation with Polylines

As it sounds like Polyline annotation also known as Lane annotation is used to draw lanes to train vehicle perception models for lane detection. Unlike bounding boxes, it avoids a lot of white space and additional noises. Annotators would simply draw lines along the boundaries you require your machine to learn.

Polyline annotation involves the creation of lines, which are used primarily to delineate boundaries between one part of an image and another. It is used when a region that needs to be annotated can be conceived of as a boundary, but it is too small or thin for a bounding box or other types of annotation to make sense.

Polylines are easy to create and commonly used for situations like training warehouse robots to recognize differences between parts of a conveyor belt, or for autonomous vehicles to recognize lanes. Since polyline annotation concerns itself with drawing attention to lines in an image, it is best used whenever important features are linear in appearance.

Some of the use cases are:

Autonomous Driving

It is a common use case for polyline annotation, as it can be used to delineate lanes on the road. Widely used in training the self-driving car perception model to recognize the various types of objects that come on the roads like traffic signals, lane obstacles, and pedestrians. All the visible objects can be easily annotated with polylines to make it recognizable for machines to understand the surroundings and move the vehicle safely while avoiding any crashes even when moving into the busy streets.


Similarly, line annotation can be used to instruct industrial robots where to place certain objects, designating a target zone as between two lines. Bounding boxes could theoretically be used for these purposes, but polyline annotation is a much cleaner solution as it avoids much of the noise that comes with using bounding boxes.


Notable computer vision use cases of polyline annotation include the automatic detection of crop rows and even the tracking of insect leg positions.

Object Detection with Robotics and Drone Imagery

Image annotation with polyline technique is also widely used to label the objects from the drone’s point of view. Images annotated with this technique are used to train drones that can identify the variety of objects on the earth.

Few of the other uses cases are, analyzing usage of nutrients and water, changes in climate, disease resistance and pest control.