# Changes between Version 31 and Version 32 of udg/ecoms

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Timestamp:
Mar 14, 2013 1:56:46 PM (9 years ago)
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 v31 }}} Currently, only the OPeNDAP access service is fully operative in the portal. Therefore, in this example, we will illustrate the use of this service, which allows selecting time/spatial data slices from the OPeNDAP data access form shown in Fig. \ref{fig:opendapwin} and downloading the resulting data in both ''ASCII'' and ''Binary'' formats. Currently, only the OPeNDAP access service is fully operative in the portal. Therefore, in this example, we will illustrate the use of this service, which allows selecting time/spatial data slices from the OPeNDAP data access form shown in figure and downloading the resulting data in both ''ASCII'' and ''Binary'' formats. [[Image(openDAPwindow.png,align=center,width=320px,title=Detail of the OPeNDAP dataset access form for a particular dataset.)]] 1. To select a variable click on the checkbox to its left. 1. To constrain the variable, edit the information that appears in the text boxes below the variable. This is a   vector of integers indicating index positions of length three, with the following order: \texttt{[start:stride:end]}. 1. To constrain the variable, edit the information that appears in the text boxes below the variable. This is a   vector of integers indicating index positions of length three, with the following order: [start:stride:end]. 1. To get ''ASCII'' or ''binary'' values for the selected variables, click on the ''Get ASCII'' or ''Get Binary'' buttons of the ''Action'' field. Note that the URL displayed in the ''Data URL'' field is updated as you select and/or constrain variables. The URL in this field can be cut and pasted in various OPeNDAP clients. The main disadvantage of the OPeNDAP service from the end-user point of view is that the specifications for subsetting dimensions are not given in their original magnitudes (i.e., latitudes and longitudes are not given in decimal degrees), but by the indexes of their position along their respective axes (note that first index value is always 0). Thus, to find out the indexes for the desired selection, we need to dump and analyze the particular values defined in the coordinate variable. For instance, Fig.~\ref{fig:latlonDump} shows the 241 values defined for the lat (latitude) coordinate, as provided by the ''Get ASCII'' option (selecting the corresponding check-box). The main disadvantage of the OPeNDAP service from the end-user point of view is that the specifications for subsetting dimensions are not given in their original magnitudes (i.e., latitudes and longitudes are not given in decimal degrees), but by the indexes of their position along their respective axes (note that first index value is always 0). Thus, to find out the indexes for the desired selection, we need to dump and analyze the particular values defined in the coordinate variable. For instance, this figure shows the 241 values defined for the lat (latitude) coordinate, as provided by the ''Get ASCII'' option (selecting the corresponding check-box). [[Image(latlonDump.png,align=center,width=320px,title=Text file displaying the values for the lat (latitude) coordinate variable.)]]