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001
Publications

2019

Development of an image-based system to assess agricultural fertilizer spreader pattern

Authors
Marcal, ARS; Cunha, M;

Publication
COMPUTERS AND ELECTRONICS IN AGRICULTURE

Abstract
An Automatic Calibration of Fertilizers (ACFert) system was developed, for use with centrifugal, pendulum or other types of broadcast spreaders which distribute dry granular agricultural materials on the top of the soil. The ACfert is based on image processing techniques and includes a specially designed mat, which should be placed in the ground for spreaders calibration. A set of images acquired outdoor by a standard device (simple camera) is used to extract information about the spreader distribution pattern. Each image is processed independently, providing as output two numerical values for each grid element present in the image - the number of fertilizers/seeds counted, and its numerical label. The performance of ACFert was evaluated for automatic granules detection using a set of manual counting measurements of nitrate fertilizer and wheat seeds. A total of 185 images acquired with two mobiles devices were used with a total of 498 quadrilateral elements observed and analysed. The overall mean absolute relative error between counting and computed by the ACFert system, were 0.75 +/- 0.75% for fertilizer and 2.12 +/- 1.68% for wheat. This near real-time calibration tool is a very low cost system that can be easily used on field, providing results to support accurate spreader calibration in near real time for different types of fertilizers or seeds.

2019

Automatic classification of coral images using colour and textures

Authors
Caridade, CMR; Marcal, ARS;

Publication
CEUR Workshop Proceedings

Abstract
The purpose of this work is to address the imageCLEF 2019 coral challenge - to develop a system for the detection and identification of substrates in coral images. Initially a revision of the 13 classes was carried out by identifying a number of sub-classes for some substrates. Four features were considered - 3 related to greyscale intensity (1) and texture (2), and 1 related to the colour content. The Breiman's Random forest algorithm was used to classify the corals in one of 13 classes defined. A classification accuracy of about 49% was obtained.

2019

Image Based Estimation of Fruit Phytopathogenic Lesions Area

Authors
Marcal, ARS; Santos, EMDS; Tavares, F;

Publication
Pattern Recognition and Image Analysis - Lecture Notes in Computer Science

Abstract

2019

Modified DBSCAN Algorithm for Microscopic Image Analysis of Wood

Authors
Martins, ALR; Marcal, ARS; Pissarra, J;

Publication
Pattern Recognition and Image Analysis - Lecture Notes in Computer Science

Abstract

2019

SEGMENTATION OF SENTINEL-2 IMAGES ON SNAP - AN EVALUATION WITH SITEF

Authors
Marcal, ARS;

Publication
2019 IEEE INTERNATIONAL GEOSCIENCE AND REMOTE SENSING SYMPOSIUM (IGARSS 2019)

Abstract
Image segmentation is widely used in image processing, particularly when there is one or few objects of interest. The segmentation of multi-spectral remote sensing images is more challenging due to the large number and diversity of the objects of interest, and the difficulty in having ground truth to tune the segmentation algorithm parameters and to evaluate the results produced. The Synthetic Image TEsting Framework (SITEF) is a tool to address these issues. As the shape and location of the objects in a synthetic image are known, it provides references to be used for quantitative evaluation of the segmentation results. This paper presents SITEF with an experiment to evaluate the segmentation of a SENTINEL-2 image using the software SNAP.

Supervised
thesis

2019

Visão Computacional para veículos aéreos não tripulados (UAV)

Author
Mónica Cristina Gandra da Rocha Salgado

Institution
UP-FCUP

2018

Towards automatic identification of woods from microscopic images

Author
Aurora Losa Ramalho Martins

Institution
UP-FCUP

2018

Extração Automática de Texto em Imagem/Vídeo

Author
Pedro Cunha Travassos

Institution
UP-FCUP

2017

Reconhecimento Automático de Sinais de Trânsito em Imagens Digitais

Author
Moisés Vungo

Institution
UP-FCUP

2017

Análise Automática de Imagens Pulmonares de Tomografia Computorizada

Author
Susana Augusta Cardoso Leal Lopes

Institution
UP-FCUP