Ortho projector to make photo maps from aerial photographs

Claim 2

Ortho projector and stereoscopic and mechanically analogously operating scanning apparatus including an autographic unit, having a scanning device with a guidance system scanning a model (12), representing a terrain profile and having profile zones, forming a first image (1), scanning being in accordance with a predetermined raster in uniform profile zones to convert perspective overlapping aerial photos (2,34) into orthographic maps comprising a guidance system (30) located and movable parallel to one of the aerial photos (2), forming a second image, in accordance with predetermined coordinates; a displacement measuring device (21, 22) measuring relative movement between the optics of the autographic unit and the aerial photo and providing digital output signals in accordance with uniform, predetermined displacement distances upon scanning; digital storing means (27) receiving and storing said step output signals at least until subsequent step output signals are received; computer means (38) connected to and receiving the step output signals of a given step (n) and of the preceding step (n-1), the computer means calculating the average image coordinate value (xon, yon) and the difference image coordinate value ( Delta xon, Delta yon); an interpolator (23) receiving the output from the computer means (38) and the stored values obtained for the adjacent position during prior scanning of the profile; means moving the other (34) of the aerial photos, and forming a third image (3), over the orthographic optic under control of the output from the interpolator; a differential distortion correction calculator (24) having the coordinate differences continuously applied thereto to calculate the re-establishment of the image and the required image enlargement and image rotation; means (25) receiving an image portion (3) from the third image and having the output of the calculated image enlargement and rotation applied thereto; and a line aperture (9) exposing the ortho photo film (6) in accordance with the image portion, as re-established and modified by the calculated enlargement and rotation, the ortho photo film being moved in accordance with the plane movement of the scanning device of the autographic unit.

Claim 3

Apparatus according to claim 1, wherein the optic of the autographic unit is positioned peRpendicularly with respect to the aerial photo.

Claim 4

Apparatus according to claim 1, wherein the predetermined coordinates are an orthogonal coordinate system.

Claim 5

Apparatus according to claim 1, wherein the digital storage means comprises a digital shift register having its inputs and outputs connected to the computer means.

Claim 6

Apparatus according to claim 1, wherein the third image (34) is pre-oriented similar to the aerial photo (2) in the autographic unit (31) so that it will have the same predetermined coordinates as the aerial photo, and said third image is moved in coordinate directions similar to the scanning by the guidance system in the predetermined raster.

Claim 7

Apparatus according to claim 1, including (FIG. 8) storage means (28) to store the image coordinates, said storage means being connected to the digital storage means (27) for subsequent reconstitution of the ortho photo.

Claim 8

Apparatus according to claim 1, including exposure control means (26) controlling exposure through the line aperture (9) to ensure uniform exposure of the ortho photo film (6).

Claim 9

Apparatus according to claim 7, including means (26'') controlling the exposure control means in accordance with speed of movement of the film, film characteristics, and enlargement factors.

Claim 10

Apparatus according to claim 1, wherein the displacement measuring device includes coordinate generator means (22) to calculate the image coordinates; and the computer means (38), the interpolator means (23) and the differential distortion correction and image calculator (24) comprise apparatus independent from the autographic unit (31) and controlling the ortho projector.

Claim 11

Apparatus according to claim 1, comprising switch-over means (32) switching the data from the displacement measuring device to predetermined addresses (27, 27'') of the digital storage means, the addresses being associated with predetermined positions of the profile of the model.

Claim 12

Apparatus according to claim 1, wherein the computer means computes the average image coordinates and the difference image coordinates in accordance with the following relationships:

Claim 13

Apparatus according to claim 1, wherein the differential distortion correction calculator (24) carries out the calculations in accordance with the following relationships:

Claim 14

Apparatus for the transformation of perspective aerial photographs into accurate ortho photographs without gaps or double images, comprising a digital store (27) for storing sequentially the rectangular image-coordinates (xn, yn; xn1, yn1) of points in one of the aerial photographs (2) of the ground which correspond to points at equal intervals of horizontal distance along profiles which are the intersections of the surface of the ground, or of a true-to-scale model (12) of the surface of the ground, and vertical planes which are parallel and at a uniform horizontal distance from one another; a first electronic computer (38) for receiving as input the image coordinates from the digital store (27) and computing the means and differences of image-coordinates of points which lie at the ends of linear image elements which correspond to line elements (3) on the surface of the ground or its model and which are uniformly spaced in horizontal distance along each profile and extend the shortest possible distance to the neighbouring profile; an interpolator (23) for receiving as one input xon, yon) the means and differences of image coordinates of the end points of successive computed linear image elements from the first computer and as a second input ( Delta xon, Delta yon) electrical signals at constant increments of horizontal distance along the profiles, these increments being smaller than the horizontal distance between the successive line elements on the surface of the ground or its model, for performing at each such electrical signal an interpolation between successive computed linear image elements, and for providing as one output (xn, yn) the image-coordinates of the middle points of interpolated linear elements and as a second output differences of image coordinates of the end points of interpolated linear image elements; a second electronic computer (24) for receiving as input said second output from the interpolator and computing the angle of rotation (r) and change of scale (v) of each interpolated linear image element which are required in order to bring them all into a common uniform scale and orientation in the horizontal plane and perpendicular to the orthogonal projection of the profiles in the horizontal plane, the uniform scale being that of the required ortho photo; a servo system driven picture carrier (34) for having mounted therein the aerial photograph (3) whose image coordinates have been determined, or a copy of this photograph, and for receiving as input said one output (xn, yn) from the interpolator (23) past an optical system which continuously collects a small area of the photographic image for subsequent processing, the centre of each such small area being the interpolated middle point of the linear image element (3) from the interpolator; an image deformation and projection unit (25) for receiving as one input the image collected by the optical system and as a second input electrical signals, which represent the computed angle of rotation (r) and change of scale (v), from the second computer (24), and for rotating and changing the scale of the collected image in accordance with the computed values, and for projecting a part of the so-deformed image orthogonally onto a moving photographic film (6) on which the ortho photo is to be produced; an exposure regulator (26) for varying the brightness of the image from the image-deformation unit in response to electrical signals which represent first (26'') an average setting for the particular conditions pertaining in the production of an ortho photo - such as the particular aerial photograph and the sensitivity of the ortho photo film emulsion -second the speed of motion (35) of the ortho photo film (6) relative to the image being projected onto the film through an aperture, and third the change of scale (36) in the image-deformation unit, so that the exposure of all parts of the ortho photo is both constant and proper for the type of film; an aperture (9) in the form of a replaceable elongated slit whose length is equal to the perpendicular distance in the horizontal plane between the profiles, in the scale of the ortho photo, and is oriented in this perpendicular direction and lies in the optical path from the exposure regulator (26) and close to the ortho photo film, so that only the rays passing through the slit reach the ortho photo film and hence a continuous series of line elements (14) from the image transmitted by the exposure regulator is exposed in the ortho photo film (6); a carrier (FIGS. 6a, 6b) for moving the ortho photo film in a scanning direction perpendicular to the line elements and so coordinated by an electrical servoloop (30) with the motion of the aerial photograph that a line element in the ortho photo always corresponds to its associated projectively transformed linear image element in the aerial photograph and therefore represents the orthogonal projectiOn onto the horizontal plane, at the ortho photo scale, of a line element on the surface of the ground which is perpendicular to the profiles and extends the shortest possible distance between profiles, the scanning motion being performed, in use, in alternate directions with automatic steps between scans, these steps being in the direction perpendicular to the profiles and of length equal to the length of the slit, so that the sum of all exposed line elements comprises a photograph of the ground at constant scale, with orthogonal projection onto the horizontal plane, and free from the effects of linear ground slope in the direction perpendicular to the profiles; and a speed sensor (35) for sensing any variation of the speed of the scan motion of the ortho photo film and providing said second signal to the exposure regulator (26).

Claim 15

Apparatus for the transformation of perspective aerial photographs into accurate ortho photographs without gaps or double images, comprising a digital store (27) for storing sequentially the rectangular image-coordinates (xn, yn; xn1, yn1) of points in one of the aerial photographs (2) of the ground which correspond to points at equal intervals of horizontal distance along profiles which are the intersections of the surface of the ground, or of a true-to-scale model (12) of the surface of the ground, and vertical planes which are parallel and at a uniform horizontal distance from one another; a first electronic computer (38) for receiving as input the image coordinates from the digital store (27) and computing the means and differences of image-coordinates of points which lie at the ends of linear image elements which correspond to line elements (3) on the surface of the ground or its model and which are uniformly spaced in horizontal distance along each profile and extend the shortest possible distance to the neighbouring profile; an interpolator (23) for receiving as one input xon, yon) the means and differences of image coordinates of the end points of successive computed linear image elements from the first computer and as a second input ( Delta xon, Delta yon) electrical signals at constant increments of horizontal distance along the profiles, these increments being smaller than the horizontal distance between the successive line elements on the surface of the ground or its model, for performing at each such electrical signal an interpolation between successive computed linear image elements, and for providing as one output (xn, yn) the image-coordinates of the middle points of interpolated linear elements and as a second output differences of image coordinates of the end points of interpolated linear image elements; a second electronic computer (24) for receiving as input said second output from the interpolator and computing the angle of rotation (r) and change of scale (v) of each interpolated linear image element which are required in order to bring them all into a common uniform scale and orientation in the horizontal plane and perpendicular to the orthogonal projection of the profiles in the horizontal plane, the uniform scale being that of the required ortho photo; a servo system driven picture carrier (34) for having mounted therein the aerial photograph (3) whose image coordinates have been determined, or a copy of this photograph, and for receiving as input said one output (xn, yn) from the interpolator (23) past an optical system which continuously collects a small area of the photographic image for subsequent processing, the centre of each such small area being the interpolated middle point of the linear image element (3) from the interpolator; an image deformation and projection unit (25) for receiving as one input the image collected by the optical system and as a second input electrical signals, which represent the computed angle of rotation (r) and change of scale (v), from the second computer (24), and for rotating and changing the scale of the collected image in accordance with the computed values, and for projecting a part of the so-deformed image orthogonally onto a moving photographic film (6) on which the ortho photo is to be produced; an exposure regulator (26) for varying the brightness of the image from the image-deformation unit in response to electrical signals which represent first (26'') an average setting for the particular conditions pertaining in the production of an ortho photo - such as the particular aerial photograph and the sensitivity of the ortho photo film emulsion -second the speed of motion (35) of the ortho photo film (6) relative to the image being projected onto the film through an aperture, and third the change of scale (36) in the image-deformation unit, so that the exposure of all parts of the ortho photo is both constant and proper for the type of film; an aperture (9) in the form of a replaceable elongated slit whose length is equal to the perpendicular distance in the horizontal plane between the profiles, in the scale of the ortho photo, and is oriented in this perpendicular direction and lies in the optical path from the exposure regulator (26) and close to the ortho photo film, so that only the rays passing through the slit reach the ortho photo film and hence a continuous series of line elements (14) from the image transmitted by the exposure regulator is exposed in the ortho photo film (6); a carrier (FIGS. 6a, 6b) for moving the ortho photo film in a scanning direction perpendicular to the line elements and so coordinated by an electrical servoloop (30) with the motion of the aerial photograph that a line element in the ortho photo always corresponds to its associated projectively transformed linear image element in the aerial photograph and therefore represents the orthogonal projectiOn onto the horizontal plane, at the ortho photo scale, of a line element on the surface of the ground which is perpendicular to the profiles and extends the shortest possible distance between profiles, the scanning motion being performed, in use, in alternate directions with automatic steps between scans, these steps being in the direction perpendicular to the profiles and of length equal to the length of the slit, so that the sum of all exposed line elements comprises a photograph of the ground at constant scale, with orthogonal projection onto the horizontal plane, and free from the effects of linear ground slope in the direction perpendicular to the profiles; and a speed sensor (35) for sensing any variation of the speed of the scan motion of the ortho photo film and providing said second signal to the exposure regulator (26).

Claim 16

Apparatus as claimed in claim 13, wherein the digital storage means (27) comprises a digital shaft register having its inputs and outputs connected to said first computer.

Claim 17

Apparatus as claimed in claim 13, wherein the second aerial photograph (3) is provided with an orientation device so that it has the same orientation relative to its guidance and coordinate system as the first photograph (2) has relative to its coordinate system when the image coordinates are measured.

Claim 18

Apparatus as claimed in claim 13, wherein (FIG. 8) external storage means (28) are provided for the storage of image coordinates in off-line usage, said external storage means being connected to the digital store (27) for the later production of ortho photographs.

Claim 19

Apparatus as claimed in claim 13, wherein said first electronic computer (38) takes as primary input any quantities from which rectangular image coordinates can be computed, and transforms these data into such rectangular, two-dimensional image coordinates for further processing in the ortho photo apparatus.

Claim 20

Apparatus as claimed in claim 13, wherein switching means (32) are provided which are operated at the ends of profiles so that image coordinates of neighbouring profiles are stored in separate halves of the digital store (27).