Introduction to the LAS version 7.1 User Interface

 

Table of Contents:

Introduction to LAS

Welcome to the the Live Access Server (LAS). LAS is a highly configurable web server designed to provide flexible access to geo-referenced scientific data. It can present distributed data sets as a unified virtual data base through the use of OPeNDAP networking. Ferret is the default visualization application used by LAS, though other applications (Matlab, IDL, GrADS, ...) can also be used.

LAS enables the web user to:

LAS enables the data provider to:

Further details about LAS may be found in the LAS documentation and the current LAS release notes.

Introduction and Overview

Here is the LAS V7.1 User Interface. This HELP document uses the NVODS server, which may be found at

http://ferret.pmel.noaa.gov/NVODS/ (National Virtual Oceanographic Data System)

 


Finding your way around

The buttons across the top bar are for opening menus, requesting a new plot, or requesting products such as animations. When a menu is open you will often see this small icon next to an item. Click on this icon for information. When it is next to a dataset in a dataset menu, this will bring up further information about the dataset. In an options menu, clicking the info icon brings up an explanation of the option.

The reference map in the upper left has its own controls along the top. In the LAS interface, hover the mouse over each for a short description, and click the ? for more help with these controls. The longitude and latitude widgets below the map may be used to enter the X and Y region desired.


Getting images and data from LAS

Example: Create a 2D xy color plot of Sea Surface Temperature from the coads climatology dataset.

Select the Coads climatology dataset: Click on the "Choose Dataset" button:


The Dataset selection tree will open. Many LAS installations use a tree of dataset categories. Click on "by Dataset Name"


and then click "Coads monthly climatology" and "Air temperature":


LAS will use your choice of data and variable and create a Latitude-Longitude map by default:

 


Using the zoom and pan reference map, you may refine the latitude and longitude displayed by the reference map; and using the selection tool the user can change the region selected. Then that region will be used when you update the plot or ask for data.

Longitude-latitude images are also interactive. This means that you can click and drag to zoom into a particular region on the image itself. Use the browser's "Back" button to return to earlier plots.

You are now free to begin interacting with LAS. For example, clicking "Time Series" on the left side of the interface will result in this image:


Customizing what you get from LAS

Example: How to modify the default values LAS uses to create an image.

In this example, we will change the specified color pallete for our AIRT plot, as well as eliminate the graticule lines. First, to change the output size of the plot, click the "Set plot options" button from the menu toolbar.

This will open up a menu from which you may change several options for plot creation. In the below - we have turned off the graticules option as well as selecting a different pallete:


After making the changes, and clicking on the "OK" button, the "Update plot" button will have changed color in the upper menu bar, like so:


When the "Update Plot" button is yellow like above, it means that the current image is out of sync with something in the User Interface. In this example, it is because the plot options have changed, but it could also happen if a different variable was selected, or a different time range was chosen, etc.

Alternatively, if the select box in the "Update plot" button is selected, then the plot will update immediately when a new selection is made.

In our example, after changing the plot options, clicking the "Update Plot" button results in the below plot. Notice that the graticule lines are no longer covering the image, and the palette is slightly different.


There are many other options that you can play with, and it's important to note that these options can be "view" specific or possibly even dataset specific.

Comparing fields with LAS

In the LAS v7.1 UI, we utilize the "Compare" button to compare data from different times or locations in a single variable, two variables in the same dataset, or variables in different datasets.

Clicking on the "Compare" button will open a new window which will contain the LAS vizGal tool:


Any plot within vizGal may be clicked, bringing it up in full-size view.

By default, all four plots are of the originaly selected date and time, but can be changed by making a selection in the Date menu on each plot:


In addition, it is now easier then ever to see anomalies with the dataset using vizGal. Clicking the "Difference Mode" button will allow you to easily see how the values from the upper left panel differ from those in the other three panels:


Note the "Gallery Settings" options on the far left. These may be used to change the plot options for all of the plots, change to another dataset and variable, or change the view. The map may be used to select sub-regions. The + in the far upper left-hand corner of this page closes (and toggles to reopen) the Gallery Setttings menus, leaving more space on the page for the four plot panels.

In the example below we choose a longitude line plot, use the "Plot Options" to choose thicker blue lines, and turn on "Difference Mode" to draw the difference from the upper left plot at each of three other times.


Each frame also has its own "settings" button. This opens an options box, which may be dragged to another location on the page.



Here there are options to change the plot options (plot style, color palette), change the variable, or even choose another dataset and variable, for comparison with the plots in other panels, either side-by-side or in Difference Mode.

Animations from LAS

From the v7.1 UI, it is also quite easy for you to view data as an animation or movie. Clicking the "Animation" button will bring up a dialog for you to specify the desired length of the animation:

 

Once the Time range is selected, and the "Submit" button pressed, each frame of the download will begin loading, and will animate as loaded:

 

Viewing data on Google Earth

LAS users can also view their data on Google Earth by clicking on the "Google Earth" button. This will bring up the current image inside of Google Earth:

NOTE: The dots on the above plot represent "placemarks" in the actual data. Clicking on a placemark will bring up a timeseries or a vertical profile of the data at that point.

Viewing and Saving data

Two buttons let you view data values or download data. "Show Values" creates a formatted listing of the currently selected variable, including a header describing the dataset, variable and subset in space and time. After choosing some data, click on "Show Values",

To see the following listing:

To save data in a file in NetCDF, ASCII or arcGrid format, use the "Save As" button. This brings up a dialog to select the format of the file to be written, and the range to save in the dimensions not chosen on the main page. In this example, ranges of Time and Depth may be chosen.

The result will be a file to download.

The remaining button at the top of the User Interface is "Export to Desktop Application". This button shows you a page showing the OPeNDAP URL for the data selected and how it can be opened with Ferret, GrADS, and Matlab to point to the current variable and region in space and time.

 

The Classic LAS UI

At the option of the LAS installer, the V6 LAS User Interface may be made available. If this option has been installed, then you may bring up the classic interface by clicking the "Use Classic LAS" link on the right side of the v7.1 UI banner.

This link will take you to the V6 UI so that you may request vector plots and some more complex comparisons.