Mound A Topographic Map
Look carefully at the topographic map of Mound A below. Notice that there are elevation lines given for every five feet, beginning with an elevation of 100 feet. These measurements do not indicate elevations above sea level. Notice that the caption for the map states that "the reference point was given an assumed elevation of 100 feet." This point became the "benchmark" for the surveyors. They simply measured elevation above or below this arbitrary point.
Some people think that the topography of Mound A looks like a bird shape. That's why Mound A is sometimes called the "Bird" Mound! What do you think? Is this nickname justified?
Contour map of Poverty Point Mound. The reference point was given an assumed elevation of 100 feet.