Startup

This is the startup screen for GridImp. GridImp works as a wizard, with each panel setting a series of parameters for the final plotting process.

The guided tour uses earthquake hazard (ground motion probability) data. This is available from the US Geological Survey free of charge. Full download details are included in the GridImp tutorial documentation.

Define the input file format

The previous panel (not shown) lets the user select an input datafile. GridImp can read a variety of text file formats.

The panel to the left shows a spreadsheet-style overview of the input data file. Each row is a data record representing a coordinate and its data value. Here the user selects which column contains which item of data. This allows GridImp to read any column configuration.

Select the output grid parameters

The next panel lets the user select the output grid extents. The example dataset extents cover the entire conterminuous USA, but we restrict the plot extents to the Western USA.

This panel can also define a new grid resolution. GridImp can interpolate the data to a different grid spacing. The second tour uses this feature to produce a finer, smoother plot.

Colors

A number of predefined colormaps (color schemes) are available. GridImp has a color editor that allows you to create your own colormap, but we will use the pre-defined Rainbow colormap for this example.

The data ranges in value from 0 (no hazard) to 138 (high hazard). We only wish to plot the elevated hazards in this example, so we set our minimum value to 30. This causes GridImp to only plot locations with a hazard above 30.

Final Plot

After setting all the parameters, GridImp starts Microsoft MapPoint and starts to plot the data. The final result is shown to the left.

Next, we look at a digital terrain (DTM) example that interpolates the data to create a smoother-looking plot.