There is a draft ASTM procedure for the method, called "Standard Test Method for Use of the Dynamic Cone Penetrometer in Shallow Pavement Applications", dated October 31, 1999. I do not know if it has been finalized. The subcommittee chair is Shiraz Tayabji, phone 410-480-1890. There is also a paper written by George Sowers which was published by ASTM in 1966, which has correlations between the DCP resistance and SPT N-values. The paper is entitled "Dynamic cone for Shallow In-Situ Penetration Testing". It was originally published in ASTM Special Technical Publication 399--you can contact ASTM to see if it is still available. The correlation between SPT N-value and the DCP resistance is not constant and depends on the soil type being tested.