A quick way to find out whether your digital terrain model file has isolated high points or spikes is to display the terrain model with a color gradient from blue to red as shown in the Global Mapper screenshot below.
In this example, the terrain surface is mostly shaded in blue tones. That is a good indication that there are some elevation spikes somewhere in your terrain model.
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A screenshot of a digital terrain model file with no high points is shown below. A good terrain surface is shaded evenly with the colors nicely balanced from blue to red as you go from lower elevations to higher elevations.
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This is one way to quickly check your digital elevation models for the presence of isolated elevation spikes.