Measurement　deviation　of　time　of　flight　(ToF)　is　inevitable　in　nondestructive　testing　based　on　the　sparse　array　and　ultrasonic　Lamb　waves.　It　affects　the　influence　zone　of　temporal-spatial　mapping　trajectories　(TSMTs)　of　signal　parameters　in　the　imaging　zone,　and　further　limits　the　quantitative　evaluation　of　defect　localization.　In　the　paper,　the　ellipse　of　uncertainty　(EOU)　of　TSMTs　was　derived　from　multiple　parameters,　including　the　group　velocity,　ToFs　and　their　measurement　deviations,　distances　between　actuators　and　receivers.　Then,　an　EOU-based　algorithm　was　developed　for　quantitative　evaluation　of　defect　localization.　The　defects　were　localized　by　searching　the　individual　scatterers　at　the　intersection　of　multiple　TSMTs.　Based　on　the　eccentricity　of　the　uncertainty　ellipse,　a　fuzzy　scaling　factor　was　introduced.　It　was　combined　with　a　fuzzy　control　parameter　to　tune　the　influence　zone　of　TSMTs.　Based　on　the　acoustic　reciprocity　theorem　and　the　fuzzy　control　parameter,　the　ToFs　of　scattering　waves　were　fused　to　establish　the　one-to-one　relation　between　individual　scatterers　and　inspection　pairs.　Experimental　results　showed　that　the　EOU-based　algorithm　can　reduce　the　interferences　of　EOU　in　the　detection;　and　the　quantitative　evaluation　of　defect　localization　was　realized　by　analyzing　the　distribution　of　individuals　and　their　ToF　difference　to　inspection　pairs.