Marcer A., Pino J., Pons X., Brotons L. (2012) Modelling invasive alien species distributions from digital biodiversity atlases. Model upscaling as a means of reconciling data at different scales. Diversity and Distributions. 18: 1177-1189.EnllaçDoi: 10.1111/j.1472-4642.2012.00911.x
Aim: There is a wealth of information on species occurrences in biodiversity data banks, albeit presence-only, biased and scarce at fine resolutions. Moreover, fine-resolution species maps are required in biodiversity conservation. New techniques for dealing with this kind of data have been reported to perform well. These fine-resolution maps would be more robust if they could explain data at coarser resolutions at which species distributions are well represented. We present a new methodology for testing this hypothesis and apply it to invasive alien species (IAS). Location: Catalonia, Spain. Methods: We used species presence records from the Biodiversity data bank of Catalonia to model the distribution of ten IAS which, according to some recent studies, achieve their maximum distribution in the study area. To overcome problems inherent with the data, we prepared different correction treatments: three for dealing with bias and five for autocorrelation. We used the MaxEnt algorithm to generate models at 1-km resolution for each species and treatment. Acceptable models were upscaled to 10 km and validated against independent 10 km occurrence data. Results: Of a total of 150 models, 20 gave acceptable results at 1-km resolution and 12 passed the cross-scale validation test. No apparent pattern emerged, which could serve as a guide on modelling. Only four species gave models that also explained the distribution at the coarser scale. Main conclusions: Although some techniques may apparently deliver good distribution maps for species with scarce and biased data, they need to be taken with caution. When good independent data at a coarser scale are available, cross-scale validation can help to produce more reliable and robust maps. When no independent data are available for validation, however, new data gathering field surveys may be the only option if reliable fine-scale resolution maps are needed. © 2012 Blackwell Publishing Ltd.
Monteagudo-Pereira J.L., Auli-Llinas F., Serra-Sagrista J., Zabala A., Maso J., Pons X. (2012) Enhanced transmission of JPEG2000 imagery through JPIP proxy and user-navigation model. Data Compression Conference Proceedings. : 22-31.EnllaçDoi: 10.1109/DCC.2012.10
The efficient transmission of large resolution images is a key aspect in many applications to minimize the transmission costs and to enhance the browsing experience. Among the currently available standards for the coding and transmission of imagery, JPEG2000 excels for its superior coding performance and advanced capabilities. The JPEG2000 Interactive Protocol (JPIP) minimizes the amount of information transmitted in a client-server scenario. Nonetheless, JPIP does not provide mechanisms to re-use data already delivered to clients browsing the same image within a local network. Common HTTP proxy servers are not able to understand the syntax of JPIP, thus specialized JPIP proxy servers are put in practice. This work improves the capabilities of traditional JPIP proxy servers by means of a user-navigation model that, together with prefetching strategies, allows the server to anticipate (potential) future requests of clients. Experimental evidence indicates that the introduction of the navigational model into a JPIP proxy server enhances the browsing experience notably. © 2012 IEEE.
More G., Pons X. (2012) Influence of the nature and number of ground control points to the quality of remote sensing geometric corrections. International Geoscience and Remote Sensing Symposium (IGARSS). : 2356-2359.EnllaçDoi: 10.1109/IGARSS.2012.6351021
Georeferencing satellite images is an essential procedure to carry out most remote sensing applications. The quality of this process will affect all the ulterior procedures and products. Independent test ground control points (GCPs) are required to assess the quality of the correction. However, a representative number is hardly obtained when they are manually located. This work studies the effect of the number of GCPs in the geometric correction quality when they are manually located. The methodology has been applied to Landsat TM images in a region with complex relief (heights ranging from 0 to 3000+ m). The work presents a spatial representation of the error and discusses its role in the visualisation of the quality. Moreover, we critically discuss the usage of indicators as the RMS error without considering the number of GCPs or the method used in their placement in the realistic assessment of the geometric quality of the imagery. Indeed, it is shown that, for the studied scenes, a minimum of 25 GCPs is needed to achieve a test RMS smaller than a pixel and that not using independent GCPs leads to unrealistic quality indicators. Moreover, manual placement of GCPs gives clearly worst results than automatic procedures. © 2012 IEEE.
Serral I., Diaz P., Maso J., Pons X. (2012) Emerging data quality from GEOSS integrated clearinghouses. International Geoscience and Remote Sensing Symposium (IGARSS). : 2744-2747.EnllaçDoi: 10.1109/IGARSS.2012.6350358
The GEOSS Common Infrastructure (GCI) provides a Clearinghouse (the GEOSS registry and metadata catalogue) and a GEOPortal to discover and visualize EO data in an integrated, standardized and interactive way, as well as broadly use it by the scientific community when dealing with representation and modeling of Earth Systems. EO data sources are ideally elaborated following quality assessment procedures, resulting in quality estimates and other related indicators. The objective of this indicators is to allow users deciding about data fitness for a purpose, but in practice systems providing methods to distribute, show and exploit this producer quality information in a standard and interoperable way are rarely used. This work aims to extract information about data quality from GCI metadata and analyze the obtained results. Additionally, an XML specific tool is able to quick and visually punctuating the metadata that refers to quality. © 2012 IEEE.
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