Distorted DEM files

Hello
      I have always had trouble with Global Mapper distorting my files vertically. For example, our county is 42 across and 30 miles north-south. When I download the county 2M DEM and measure it with the Global Mapper tool it measures 42 x 30 miles, however the actual area I am looking at is only 42 x 15 miles. The Y axis is stretched by a factor of 2. The shape of the county appears correct but I only have half the data. The bottom half is chopped off and the remaining  top half of the county stretched to the proper outline of the county. Do I have a setting wrong?
                                                                                                                          Dave

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