A computer-implemented method of determining a pose of a surgical registration device , wherein the surgical registration device comprises a surface and at least one optical pattern arranged on the surface, the method comprising: obtaining an image of at least a first part of the surgical registration device in a first pose; detecting the at least one optical pattern in the image; obtaining surface model data describing a surface of at least a second part of the surgical registration device; obtaining first location information indicating a location of the at least one optical pattern with respect to the surface of the surgical registration device; determining , based on the detected at least one optical pattern, the surface model data and the first location information, a second pose of the surface of the surgical registration device; obtaining depth information describing three-dimensional coordinates of the surface of at least the second part of the surgical registration device in the first pose; and determining , based on the second pose, the surface model data and the depth information, a third pose of the surface of the surgical registration device, wherein the second pose and the third pose each describe a relative spatial relationship between the surgical registration device and a sensor device comprising at least one sensor configured to obtain at least one data chosen from the depth information and the image, wherein determining the second pose comprises extracting information from the detected at least one optical pattern , the information indicating a known relative spatial relationship between the surgical registration device and a tracking system of a surgical navigation system , wherein the method further comprises determining, based on the third pose and the known relative spatial relationship between the surgical registration device and the tracking system , a relative spatial relationship between the sensor device and the tracking system . obtaining an image of at least a first part of the surgical registration device in a first pose; detecting the at least one optical pattern in the image; obtaining surface model data describing a surface of at least a second part of the surgical registration device; obtaining first location information indicating a location of the at least one optical pattern with respect to the surface of the surgical registration device; determining , based on the detected at least one optical pattern, the surface model data and the first location information, a second pose of the surface of the surgical registration device; obtaining depth information describing three-dimensional coordinates of the surface of at least the second part of the surgical registration device in the first pose; and determining , based on the second pose, the surface model data and the depth information, a third pose of the surface of the surgical registration device, wherein the second pose and the third pose each describe a relative spatial relationship between the surgical registration device and a sensor device comprising at least one sensor configured to obtain at least one data chosen from the depth information and the image, wherein determining the second pose comprises extracting information from the detected at least one optical pattern , the information indicating a known relative spatial relationship between the surgical registration device and a tracking system of a surgical navigation system , wherein the method further comprises determining, based on the third pose and the known relative spatial relationship between the surgical registration device and the tracking system , a relative spatial relationship between the sensor device and the tracking system . <EOS>