A method comprising: determining (1400, 1500) locations of a plurality of candidate landmarks in relation to a robot (120, 600, 700, 1000, 1100) based on sensor data from at least one sensor (322, 602, 702, 1002) of the robot; determining (1402, 1502) a plurality of sample sets, wherein each sample set comprises a subset of the plurality of candidate landmarks (712, 1012, 1014, 1016, 1018, 1020, 1112, 1114, 1116, 1118, 1120, 1214, 1216, 1218, 1312, 1314, 1316, 1318, 1320, 1322) and a plurality of corresponding mapped landmarks (704, 902, 904, 906, 908, 1102, 1104, 1106, 1108, 1204, 1206, 1208, 1302, 1304, 1306, 1308); characterised in that for each sample set of the plurality of sample sets: determining a transformation that relates the candidate landmarks from the subset of the plurality of candidate landmarks to the corresponding mapped landmarks of the plurality of corresponding mapped landmarks; applying the determined transformation to the plurality of candidate landmarks; and determining a number of inliers associated with the sample set based on distances between the transformed plurality of candidate landmarks and a plurality of neighbouring mapped landmarks; selecting a sample set from the plurality of sample sets based on the determined number of inliers associated with each sample set from the plurality of sample sets; and estimating a pose of the robot based on the selected sample set. determining (1400, 1500) locations of a plurality of candidate landmarks in relation to a robot (120, 600, 700, 1000, 1100) based on sensor data from at least one sensor (322, 602, 702, 1002) of the robot; determining (1402, 1502) a plurality of sample sets, wherein each sample set comprises a subset of the plurality of candidate landmarks (712, 1012, 1014, 1016, 1018, 1020, 1112, 1114, 1116, 1118, 1120, 1214, 1216, 1218, 1312, 1314, 1316, 1318, 1320, 1322) and a plurality of corresponding mapped landmarks (704, 902, 904, 906, 908, 1102, 1104, 1106, 1108, 1204, 1206, 1208, 1302, 1304, 1306, 1308); characterised in that for each sample set of the plurality of sample sets: determining a transformation that relates the candidate landmarks from the subset of the plurality of candidate landmarks to the corresponding mapped landmarks of the plurality of corresponding mapped landmarks; applying the determined transformation to the plurality of candidate landmarks; and determining a number of inliers associated with the sample set based on distances between the transformed plurality of candidate landmarks and a plurality of neighbouring mapped landmarks; determining a transformation that relates the candidate landmarks from the subset of the plurality of candidate landmarks to the corresponding mapped landmarks of the plurality of corresponding mapped landmarks; applying the determined transformation to the plurality of candidate landmarks; and determining a number of inliers associated with the sample set based on distances between the transformed plurality of candidate landmarks and a plurality of neighbouring mapped landmarks; selecting a sample set from the plurality of sample sets based on the determined number of inliers associated with each sample set from the plurality of sample sets; and estimating a pose of the robot based on the selected sample set.