Section: 3.2.12 Working with Large Grids

3.2.12 Working with Large Grids

Displaying high resolution grids in the IDV can be memory intensive. If you are reading from a remote server, you also have to deal with the latency of reading the grids across the internet. There are several strategies you can use to reduce the amount of memory used by the IDV.

First, let's load in a high resolution grid.
- If you have not already done so, use the Edit→Remove All Displays and Data menu to remove the displays created in the previous exercise.
- In the Catalog data chooser, select the Main IDV Catalog→Unidata IDD Model Data→UCAR(motherlode)→North American Model→NCEP NAM CONUS 12 km→latest NCEP NAM CONUS 12km dataset.
Now, let's subset the grid.
- Open the Data Source Properties editor for Latest NCEP NAM CONUS 12km.
- You can subset the grid by time and/or by coverage.
  - Click on the Times tab. select the Use Selected menu item. Right click on the panel and select the Select every third one menu option.
  - Click on the Spatial Subset tab. You can spatially subset the grid by stride (e.g. every nth point) and/or by region. Set the X Stride to Every third point. Notice that the Y Stride is linked to the X Stride.
  - Optionally, keep the stride at All points and select a sub-region on the map.
- In the Field Selector, select the 3D grid->Temperature @ pressure field and the Contour Plan View display.
- Since we are displaying a single level, you can further reduce the grid by selecting a level instead of the entire grid. In the Level tab of the Data Subset panel, select the 50000 Pa (500 millibar) level.
- Click the Create Display button.
For more information on performance tuning, see the Performance Tuning section of the IDV User's Guide.

Unidata IDV Workshop for version 6.3 > Accessing and Displaying Data > Working with Gridded Data