IMAGE RECTIFIER

• US 3,614,410 A
• Filed: 06/12/1969
• Issued: 10/19/1971
• Est. Priority Date: 06/12/1969
• Status: Expired due to Term

• Current Assignee: Dudley P. Hattaway, Knight V. Bailey
• Original Assignee: Dudley P. Hattaway, Knight V. Bailey
• Inventors: Bailey, Knight V., Hattaway, Dudley P.
• Primary Examiner(s): Botz, Eugene G.
• Assistant Examiner(s): Dildine, Jr., R. Stephen
• Application Number:
  US04/832,808
• Time in Patent Office: 859 Days
• Field of Search: 346/29,31 318/637 235/186,189 95/12.5 33/1A,18C,25D
• US Class Current: 358/1.6
• CPC Class Codes: B43L 13/022 automatic apparatus for recording measured values G01D; control systems for drawing machines G06K15/22, G06F3/13
• CPC Class Codes: G06G 7/22 for evaluating trigonometric functions; for conversion of co-ordinates; for computations involving vector quantities trigonometric computations using simultaneous equations G06G7/34 for computations in the complex plane; G06G7/20, G06G7/28 take precedence

Abstract

This invention is directed to an apparatus that plots an orthogonal projection of a photograph or similar image which was taken at an angle to the earth'"'"''"'"'s surface. A stylus is used to outline the image which is to be rectified. The x and y cartesian coordinates of the stylus position are fed to an analog computer together with data relating to the camera'"'"''"'"'s position at the time the image was taken. The computer, utilizing trigonometric relationships, calculates rectified equivalents of the X, y coordinates. These equivalents are utilized to motivate a plotter which traces a rectified drawing of the input image.

Claims

1. A method of making a rectified line drawing from an aerial image taken at an angle to the earth comprising the steps of aligning a photograph about an x, y axis;

tracing the photograph to obtain the x and y coordinates of various points thereon;

compensating the x and y coordinates to cancel the effects of the aircraft position at the time the photograph was taken; and

tracing the compensated x and y coordinates upon a recording medium.

2. The method of claim 1 wherein said tracing step includes the step of computing the x and y coordinates from their trigonometrical equivalents.

3. The method of claim 2 where a stylus having a first and second arm is utilized in said tracing step and wherein the step of computing implements the equations x a cos gamma - b cos Beta y a sin gamma - b sin Beta where a and b are the lengths of the first and second arm, respectively of said stylus, and gamma and Beta are the acute angles of the arms with respect to the preselected x-axis.

4. The method of claim 1 wherein the compensating step comprises the steps of first rotating the x and y coordinates through the swing angle K of the aircraft and secondly rotating the x and y coordinates through the roll angle omega of the aircraft and thirdly Rotating the x and y coordinates through the pitch angle phi of the aircraft.

5. The method of claim 4 wherein said step of first rotating the x and y coordinates through the swing angle K implements the equations x1 x cos K - y sin K y1 x sin K + y cos K z1 -f where f is the focal length of the photograph.

6. The method of claim 5 where the step of secondly rotating the x and y coordinates through the roll angle omega implements the equations x2 x1 y2 y1 cos omega - z1 sin omega z2 y1 sin omega + z1 cos omega

7. The method of claim 6 where the step of thirdly rotating the x and y coordinates through the pitch angle phi implements the equations x3 x2 cos phi - z2 sin phi y3 y2 z3 x2 sin phi + z2 cos phi

8. The method of claim 7 wherein said tracing step includes the step of computing the x and y coordinates from their trigonometrical equivalents.

9. The method of claim 8 where a stylus having a first and second arm is utilized in said tracing step and wherein the step of computing implements the equations x a cos gamma - b cos Beta y a sin gamma + b sin Beta where a and b are the lengths of the first and second arm, respectively of said stylus, and gamma and Beta are the acute angles of the arms with respect to the preselected x-axis.

10. An apparatus for producing rectified line drawings from an aerial image comprising a stylus for tracing an aerial image;

measuring means connected to said stylus for yielding an output indicative of said stylus position;

analog-computing means connected to said measuring means and operable to provide rectification compensation for the position of the aircraft at the time the aerial image was taken; and

plotting means connected to the output of said analog-computing means for tracing a rectified drawing of said aerial image.

11. An apparatus as in claim 10 wherein said measuring means utilizes angular resolvers.

12. An apparatus as in claim 11 wherein said aerial image is aligned along an x and y axis;

said stylus has a first and second arm; and

said measuring means comprises a first and second resolvers connected to said first and second arms to provide a measurement of the x and y coordinates of the stylus position.

13. An apparatus as in claim 12 wherein said first and second resolvers implements the equations x a cos gamma - b cos Beta y a sin gamma + b sin Beta where a and b are the lengths of the first and second arms and gamma and Beta are the acute angles of the arms with respect to the preselected x-axis.

14. An apparatus as in claim 12 wherein said analog computer utilizes a first computing resolver for compensating for the swing angle K of an aircraft, a second computing resolver for compensating for the roll angle omega of an aircraft and a third resolver for compensating for the pitch angle phi of an aircraft.

15. An apparatus as in claim 14 wherein said analog computer utilizes adjustable controls for setting each computing resolver according to the angle for which it compensates.

16. An apparatus as in claim 15 wherein said first computing resolver is connected to receive the x and y readings from said first and second resolvers and implements the following equations x1 x cos K - y sin K y1 x sin K + y sin K where x1 and y1 are the outputs of the resolver.

17. An apparatus as in claim 16 wherein said second computing resolver is connected to receive the y1 output of said first computing resolver and the focal length f of the aerial image and implements the following equations:

y2 y1 cos omega - z1 sin omega z2 y1 sin omega + z1 cos omega where z1 f and y2 and z2 are the outputs of the resolver.

18. An apparatus as in claim 17 wherein the third computing resolver is connected to receive the x1 and z2 outputs and implements the equations:

x3 x2 cos phi - z2 sin phi z3 x2 sin phi + z2 cos phi where x1 x2 and x3 and z3 are outputs of said resolver.

19. An apparatus as in claim 18 wherein the plotting means includes:

a first and second servomotor means;

said first motor being connected to receive the x3 and z3 outputs of said computing resolvers and said second motor being connected to receive the y2 and z3 outputs of said computing resolvers;

a movable arm connected to said first servo for movement in the x direction; and

a pen mounted on said movable arm and operable to be driven the y direction by said second servomotor.