This paper defines a new methodology for evaluating edge detectors through measurements on edginess maps instead of on binary edge maps as previous methodologies do. These measurements avoid possible bias introduced by the applicationdependent process of generating binary edge maps from edginess maps. The features of completeness, discriminability, precision and robustness, which a general-purpose edge detector must comply with, are introduced. The R, DS, P and F AR-measurements in addition to P SNR applied to the edginess maps are defined to assess the performance of edge detection. The R, DS, P and F AR-measurements can be seen as generalizations of previously proposed measurements on binary edge maps. Well-known and state-of-the-art edge detectors have been compared by means of the new proposed metrics. Results show that it is difficult for an edge detector to comply with all the proposed features.

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Several authors insist on the importance of students' acquisition of spatial abilities and visualization in order to have academic success in areas such as science, technology or engineering. This paper proposes to discuss and analyse the use of educational robotics to develop spatial abilities in 12 year old students. First of all, a course to introduce robotics to 6th grade primary school students was designed. The key intention was to prepare practical and motivating sessions in order to foster the students' involvement in hands-on learning. Hence, during the sessions of the course, challenges were provided for the students, in order to develop their capabilities as proficient problem solvers. The teacher assisted and guided the students, and the students were encouraged to solve the problems by themselves, working in 3-members teams. The main goal of this paper is to discuss and analyse the potential usefulness of educational robotics to develop spatial abilities. To carry out the analysis, students were randomly divided into an experimental group (EG), which participated in the robotics course, and a control group (CG), which did not take part in the robotics course. The extensive existing literature for spatial ability evaluation was analysed and reviewed and a pre-test and a post-test were prepared for use in the research study. Initially, the spatial ability of both EG and CG students was assessed with the pre-test. Then, after finishing the robotics course, the same sets of students were tested with the post-test. An extensive analysis of the results is provided in the paper. Results show that the positive change in spatial ability of the participants in the robotics course (EG) was greater than change evident in the students who did not join the course (CG). The improvement was statistically significant. The results also show that the overall performance of the students depends on the instruments used to evaluate their spatial abilities. Hence, this study manifests clearly the importance of the selection of those instruments.

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