A computer-implemented method for assessing a vessel, the method comprising the steps of: obtaining a set of first location pressure measurements at a first location in the vessel over a first time period and a set of second location pressure measurements at a second location in the vessel over the first time period, wherein the second location is different than the first location, and wherein the set of first location pressure measurements and the set of second location pressure measurements are obtained not during hyperemia; identifying a first leading characteristic associated with one or more pressure measurements in the set of first location pressure measurements and a second leading characteristic associated with one or more pressure measurements in the set of second location pressure measurements; identifying a first trailing characteristic associated with one or more pressure measurements in the set of first location pressure measurements and a second trailing characteristic associated with one or more pressure measurements in the set of second location pressure measurements, wherein the identified first trailing characteristic is after the identified first leading characteristic in the first time period and the identified second trailing characteristic is after the identified second leading characteristic in the first time period, and wherein at least one of the identified first leading characteristic, the identified second leading characteristic, the identified first trailing characteristic, and the identified second trailing characteristic is associated with a pressure measurement in the respective set of first location pressure measurements and second location pressure measurements that is obtained without reference to any dicrotic notch that may be present in the respective set of first location pressure measurements and second location pressure measurements; and calculating a pressure ratio using i) a pressure measurement in the set of first location pressure measurements between the identified first leading characteristic and the identified first trailing characteristic and ii) a pressure measurement in the set of second location pressure measurements between the identified second leading characteristic and the identified second trailing characteristic. obtaining a set of first location pressure measurements at a first location in the vessel over a first time period and a set of second location pressure measurements at a second location in the vessel over the first time period, wherein the second location is different than the first location, and wherein the set of first location pressure measurements and the set of second location pressure measurements are obtained not during hyperemia; identifying a first leading characteristic associated with one or more pressure measurements in the set of first location pressure measurements and a second leading characteristic associated with one or more pressure measurements in the set of second location pressure measurements; identifying a first trailing characteristic associated with one or more pressure measurements in the set of first location pressure measurements and a second trailing characteristic associated with one or more pressure measurements in the set of second location pressure measurements, wherein the identified first trailing characteristic is after the identified first leading characteristic in the first time period and the identified second trailing characteristic is after the identified second leading characteristic in the first time period, and wherein at least one of the identified first leading characteristic, the identified second leading characteristic, the identified first trailing characteristic, and the identified second trailing characteristic is associated with a pressure measurement in the respective set of first location pressure measurements and second location pressure measurements that is obtained without reference to any dicrotic notch that may be present in the respective set of first location pressure measurements and second location pressure measurements; and calculating a pressure ratio using i) a pressure measurement in the set of first location pressure measurements between the identified first leading characteristic and the identified first trailing characteristic and ii) a pressure measurement in the set of second location pressure measurements between the identified second leading characteristic and the identified second trailing characteristic.