Measurements of top quark pair and single top total cross sections, and in-situ systematic constraints

Measuring the total cross sections of top quark pair production and single top processes at high precision tests the predictions of the Standard Model and can bring better understanding of properties such as the top quark mass, electroweak couplings, lepton universality and proton p.d.fs. Some of the recent measurements by the ATLAS and CMS experiments at the Large Hadron Collider are outlined in this document. Experimental methods are given particular attention, particularly the determination of lepton isolation efficiencies in the ATLAS dilepton measurement of tt production.