GridComp faq

Grid Comparison Tool instructions

http://neisgei.org/GridComp

Choosing a Dataset

There are currently 4 default datasets immediately available, but any dataset present in the datafed wiki RSS catalog may be brought into the application.

To choose a dataset from the catalog, select "Choose new dataset" from either map's dataset drop down menu. The Grid datasets from the datafed catalog will pop up in a new window.

From here, you may search for values in a number of fields, view the dataset's metadata, or select the dataset to bring it into the Grid Comparison Tool application. The chosen dataset will be available for both grids, and you may select as many at a time as you wish.

Choosing a Time

Once you have selected a dataset, you will notice the time range available for that dataset and the frequency of data available below the options.

You have the option to view a single instance of this dataset, or combine data from multiple time periods. If you wish to view a single instance, set the year, month, day, and hour to an available time. NOTE: Daily, Monthly, and Yearly datasets have data recorded at the beginning of each period. For example, ABBI is a monthly dataset, thus data is only available on the first day and first hour of each month. Make sure hour is set to 0 and day is set to 1 for monthly datasets.

If you wish to select a range of dates, change the Time selection box to "Time Range". You will notice the Year,Month,Day,and Hour selection boxes are now disabled. To select a time range, use the Time filters that have appeared to the right. Use control+click to select any number of years and months available to the dataset, followed by the operation you wish to perform to aggregate the data.

Preview a Dataset

Once you have selected a time and dataset, you may set a scale minimum and maximum for the window. There are 6 colors displayed in the map, ranging from blue at the scale min to red at the scale max. Note: This scale is only for this map. You may use exponents in the form "5e05" or "2e-09" or negative numbers. Preview the data by selecting "Update Map".

Performing a Calculation

Now that you have two datasets and a time selected, you may compare these datasets with the options to the right of the big map. Choose an expression, a scale, and a resolution for the resulting data. Custom expressions are allowed by choosing "Custom" from the expression drop down box. Type in your custom expression in the text input that has become available. Use "a" to refer to your left grid and "b" to refer to your right grid dataset.