Spatiotemporal patterns of Sentinel-2 observations at image- and pixel-level of the Mexican territory between 2015 and 2019

[ES] Actualmente, las imágenes Sentinel-2 son uno de los acervos multiespectrales y gratuitos de mayor resolución temporal, espectral y espacial para monitorear la superficie terrestre. Sin embargo, la posibilidad de utilizar este acervo para distintas aplicaciones está condicionada por el número de observaciones sin nubes disponibles para una ventana espacio-temporal determinada. Por ello, este artículo tuvo el objetivo de analizar el número de observaciones de Sentinel-2 disponibles para el territorio mexicano a nivel de imagen y de pixel. En el primer caso, se contabilizó el total de imágenes disponibles por año y su porcentaje de nubosidad; mientras que, en el segundo, se calculó el número de observaciones despejadas por pixel. Además, para tomar en cuenta la diversidad del territorio, se evaluó el promedio mensual de las observaciones por pixel de cada una de las siete ecorregiones del país, así como la proporción de su superficie con por lo menos una observación despejada en intervalos mensuales, bimestrales, trimestrales y anuales. Los resultados mostraron que el número de observaciones válidas por pixel variaron entre 0 y 121 observaciones al año y entre 0 y 6.58 al mes. Adicionalmente, se observó que en el periodo 2017 – 2019 se pueden obtener observaciones de todo el país en ventanas anuales, mientras que en el periodo 2018 – 2019, se pueden obtener observaciones en intervalos mensuales o trimestrales, dependiendo de la ecorregión. Finalmente, consideramos que los resultados de este trabajo servirán de guía para los usuarios interesados en utilizar estas imágenes para distintos estudios.[EN] Sentinel-2 imagery has the highest temporal, spectral and spatial resolution to monitor land surface among the freely available multispectral collections. However, the possibility to use these images in different applications is conditioned by the number of cloudless observations available for a certain spatiotemporal window. Thus, the objective of this article is to analyze the number of Sentinel-2 observations available for the Mexican territory at image and pixel level. In the first case, the total number of available images and its cloud cover percentage was calculated; while in the second case, the number of cloudless observations was estimated for each pixel. Additionally, in order to take into account the territory diversity, the monthly mean number of cloudless observations, as well as the proportion of its surface with at least one cloudless observation in monthly, bimonthly, trimonthly and annual intervals, was computed for each one of the seven ecoregions of the country. The results show that annually, the number of valid observations per pixel is between 0 and 121 observations, while in monthly evaluations, between 0 and 6.58 observations. Additionally, in the 2017-2019 period annual observations can be obtained for the entire Mexican land surface, while in 2018-2019, monthly or trimonthly evaluations can be achieved, depending on the ecoregion. We consider that these results will provide useful information for researchers that are interested in using Sentinel-2 imagery for different applications.El primer autor agradece al CONACyT por la beca otorgada para realizar sus estudios de posgrado. Agradecemos a dos revisores anónimos por sus comentarios que nos ayudaron a mejorar significativamente el manuscrito de este artículoSolórzano, J.; Mas, J.; Gao, Y.; Gallardo-Cruz, J. (2020). Patrones espaciotemporales de las observaciones de Sentinel-2 a nivel de imagen y píxel sobre el territorio mexicano entre 2015 y 2019. Revista de Teledetección. 0(56):103-115. https://doi.org/10.4995/raet.2020.14044OJS10311505

Quantitative Assessment of Emphysema Severity in Histological Lung Analysis

15 págs.; 8 figs.; 1 tab.© 2015, Biomedical Engineering Society. Emphysema is a characteristic component of chronic obstructive pulmonary disease (COPD), which has been pointed out as one of the main causes of mortality for the next years. Animal models of emphysema are employed to study the evolution of this disease as well as the effect of treatments. In this context, measures such as the mean linear intercept (Lm) and the equivalent diameter (d) have been proposed to quantify the airspace enlargement associated with emphysematous lesions in histological sections. The parameter D2, which relates the second and the third moments of the variable d, has recently shown to be a robust descriptor of airspace enlargement. However, the value of D2 does not provide a direct evaluation of emphysema severity. In our research, we suggest a Bayesian approach to map D2 onto a novel emphysema severity index (SI) reflecting the probability for a lung area to be emphysematous. Additionally, an image segmentation procedure was developed to compute the severity map of a lung section using the SI function. Severity maps corresponding to 54 lung sections from control mice, mice induced with mild emphysema and mice induced with severe emphysema were computed, revealing differences between the distribution of SI in the three groups. The proposed methodology could then assist in the quantification of emphysema severity in animal models of pulmonary disease.J. Victor Marcos is a research fellow at Institute of Optics (CSIC) under the ‘‘Juan de la Cierva’’ program funded by the Spanish Ministry of Economy and Competitiveness. This work has been partly funded by the grants ‘‘MINECO DPI2012-38090-C03-02’’ and ‘‘TEC2013-48552-C2-1-R’’ from the Spanish Ministry of Economy and Competitiveness.Peer Reviewe

Sistemas aéreos pilotados de forma remota y clasificación orientada a objetos: un acercamiento al análisis submétrico de una zona periurbana

Los RPAS (Sistemas Aéreos Pilotados de Forma Remota) han abierto la posibilidad de generar imágenes multiespectrales submétricas con costos relativamente bajos y de buena calidad. Al utilizar estas imágenes con metodologías de clasificación precisas, como la orientada a objetos, se deberían obtener excelentes resultados. Por ello, el objetivo de esta investigación fue evaluar el potencial de este tipo de clasificación utilizando imágenes obtenidas con un RPAS para generar un mapa temático de una escena suburbana. La clasificación resultó exitosa (fiabilidad total = 0.83) y permitió discernir trece categorías focales y una sin clasificar. Dentro de la clasificación fue posible distinguir entre cobertura urbana de diferentes alturas, cinco tipos de vegetación y cuerpos de agua

Deforestation and trends of change in protected areas of the Usumacinta River basin (2000–2018), Mexico and Guatemala

Deforestation is one of the processes that most impact the functioning of terrestrial ecosystems. In Mexico and Guatemala, deforestation continues to increase at alarming rates, but there are still regions where extended areas of conserved vegetation persist, such as the Usumacinta River basin. Throughout history, various protected areas (PA) have been designated in this basin; however, anthropogenic activities put its natural heritage at risk. This research aimed to analyze the current status and process of forest cover loss in the region and compare it within and outside PA, as well as among different PA administrations. In 2000, 75% of the basin’s area was covered by some type of tree-dominated plant community. Over the following 18 years, this area was reduced by 27%. Most of this forest loss occurred in Guatemalan territory. Although the net forest loss was higher in unprotected areas than in protected areas in Guatemala, the opposite pattern was observed in terms of the annual rate of forest loss. In the case of Mexico, forest loss was higher in unprotected areas in terms of both net forest loss and annual rates. Additionally, in both countries, PA under the administration of municipal authorities showed the lowest forest loss rates. This study showed that deforestation is an ongoing process in the Usumacinta basin with a heterogeneous spatial distribution, where PA have had different capabilities in helping conserve its forest cover. This information will be essential for binational conservation strategies aimed at preserving forest connectivity in the region