PASCAL Visual Object Classes Challenge 2007 (VOC2007) Annotation Guidelines

This document reproduces the guidelines used for annotating images in the VOC2007 data set.

Guidelines on what and how to label


What to label

All objects of the defined categories, unless:

  • you are unsure what the object is.
  • the object is very small (at your discretion).
  • less than 10-20% of the object is visible.

If this is not possible because too many objects, mark image as bad.


Record the viewpoint of the ‘bulk’ of the object e.g. the body rather than the head.  Allow viewpoints within 10-20 degrees.

If ambiguous, leave as ‘Unspecified’.

Bounding box

Mark the bounding box of the visible area of the object (not the estimated total extent of the object).

Bounding box should contain all visible pixels, except where the bounding box would have to be made excessively large to include a few additional pixels (<5%) e.g. a car aerial.

Occlusion/ truncation

If more than 15-20% of the object is occluded and lies outside the bounding box, mark as ‘Truncated’.

Do not mark as truncated if the occluded area lies within the bounding box.

Image quality/ illumination

Images which are poor quality (e.g. excessive motion blur) should be marked bad.  However, poor illumination (e.g. objects in silhouette) should not count as poor quality unless objects cannot be recognised.

Images made up of multiple images (e.g. collages).

Clothing/mud/ snow etc.

If an object is ‘occluded’ by a close-fitting occluder e.g. clothing, mud, snow etc., then the occluder should be treated as part of the object.


Do label objects visible through glass, but treat reflections on the glass as occlusion.


Do label objects in mirrors.


Label objects in pictures/posters/signs only if they are photorealistic but not if cartoons, symbols etc.

Guidelines on categorisation



Includes gliders but not hang gliders


Includes tricycles, unicycles


Ships, rowing boats, pedaloes but not jet skis


Plastic, glass or feeding bottles


Includes minibus


Includes cars, vans, people carriers etc.

Do not label where only the vehicle interior is shown.


Domestic cats (not lions etc.)


Includes armchairs, but not stools or benches

Dining table

Excludes coffee table or picnic bench


Domestic dogs (not wolves etc.)


Includes ponies, donkeys, mules etc.


Includes mopeds, scooters, sidecars

Potted plant

Indoor plants or outdoor plants clearly in a pot.  Excludes flowers in vases


Excludes sofas made up as sofabeds


Includes train carriages, excludes trams


Standalone screens (not laptops), not advertising displays

Guidelines on segmentation


What to segment

Objects whose bounding boxes have been labelled according to the above guidelines.

You may need to exclude backpacks, handbags etc. which were included in the bounding box.


Segment within 5 pixels.  Labelled pixels MUST be the object;
 pixels outside the 5-pixel border area MUST be background.  Border pixels can be either.  Use the tri-map displayed by the segmentation tool to ensure these constraints hold.


This may occasionally involve labelling pixels outside the bounding box.

Mixed pixels

Pixels which are mixed e.g. due to transparency, motion blur or the presence of a border should be considered to belong to the object whose colour contributes most to the mix.

Thin structures

Aim to capture thin structures where possible, within the accuracy constraints.  Structures of around one pixel thickness can be ignored e.g. wires, rigging.

Objects on tables etc.

If a number of small objects are occluding an object e.g. cutlery/silverware on a dining table, they can be considered part of that object.

Difficult images

Images which are overly difficult to segment to the required accuracy can be left unlabelled e.g. a nest of bicycles.