A new method is proposed to estimate porosity within heterogeneous karst aquifers using techniques borrowed from remote sensing and geospatial analysis. High-resolution borehole images are classified into binary images consisting of pixels designated as either rock matrix or pore space. Two-dimensional porosity is calculated by summing the total area occupied by pores within a rectangular sampling window placed over the binary image. Small sampling windows quantify the heterogeneous nature of porosity distribution in the aquifer, whereas large windows provide an estimate of overall porosity. Applying this procedure to imagery taken from the Biscayne aquifer of south Florida yields a porosity...