A method for a three dimensional surveying of a 3D-scene for deriving a true-to-size 3D-model. It involves deriving a first 3D-partial-model of a section of the 3D-scene together with a capturing of at least one first 2D-visual-image and a second 3D-partial-model of another section of the 3D-scene, together with a capturing of at least one second 2D-visual-image, wherein the 3D-partial-models are partially overlapping. The first 3D-partial-model is conglomerated with the second 3D-partial-model to form the 3D-model of the 3D-scene, which is done with defining a first line segment in the first 2D-visual-image and a second line segment in the second 2D-visual-image, which first and second line segments are representing a visual feature, which is common in both of the 2D-visual-images. The line segments in the 2D-visual-images are utilized in conglomerating the corresponding 3D-partial models to form the 3D-model of the whole 3D-scene.