Wide-area aerial camera systems

Abstract

A system for capturing aerial images, the system comprising four steerable detail camera modules, each steerable detail camera module comprising a detail camera and a beam-steering mechanism in an optical path of the detail camera module whereby the pointing direction of the detail camera is time-multiplexed to provide a wider effective field of view, the beam-steering mechanism comprising a first steerable mirror.

1 - 20 . (canceled) 
     
     
         21 . A method of imaging a survey area, the method comprising:
 (a) flying an aircraft above the survey area along a set of flight lines;   (b) capturing, during flight and via a plurality of detail cameras carried by the aircraft, a set of detail images, each detail image depicting a part of the survey area; and   (c) steering, during flight, a pointing direction of each detail camera along a corresponding steering axis, thereby to capture a subset of the detail images along the steering axis;   wherein each steering axis is angled at substantially 45 degrees to a direction of flight, and at least two of the steering axes are angled at substantially 90 degrees to each other.   
     
     
         22 . The method of  claim 21 , wherein the pointing direction during steering varies from substantially vertical to at least 45 degrees from vertical. 
     
     
         23 . The method of  claim 21 , wherein each image in the subset of images at least partially overlaps its successor image. 
     
     
         24 . The method of  claim 21 , wherein each subset of images at least partially overlaps its successor subset of images. 
     
     
         25 . The method of  claim 21 , wherein the direction of flight is angled at approximately 45 degrees to a cardinal direction. 
     
     
         26 . The method of  claim 21  further comprising utilizing an angular motion compensation mechanism to correct the effect, on each detail camera, of angular motion of the aircraft, thereby to ensure the detail cameras point in a consistent direction over time. 
     
     
         27 . The method of  claim 21  further comprising utilizing a forward motion compensation mechanism to correct the effect, on each detail camera, of forward motion of the aircraft, thereby to reduce motion blur in the images captured by the detail cameras. 
     
     
         28 . The method of  claim 21  further comprising:
 identifying, in a plurality of the detail images, common features corresponding to common ground points; 
 estimating, via bundle adjustment and using locations of the identified ground points in the detail images, a camera pose associated with each detail image and a three-dimensional position associated with each ground point; 
 orthorectifying each of a plurality of the detail images at least partly in reliance on its corresponding camera pose and at least partly in reliance on some of the estimated three-dimensional ground point positions; and 
 merging the orthorectified detail images to create an orthomosaic of the survey area. 
 
     
     
         29 . The method of  claim 21  further comprising capturing, during flight and via at least one overview camera carried by the aircraft, a sequence of overview images, the focal length of the overview camera shorter than the focal length of each detail camera. 
     
     
         30 . The method of  claim 29  further comprising:
 identifying, in a plurality of the overview images and detail images, common features corresponding to common ground points; 
 estimating, via bundle adjustment and using locations of the identified ground points in the overview images and detail images, a camera pose associated with each detail image and a three-dimensional position associated with each ground point; 
 orthorectifying each of a plurality of the detail images at least partly in reliance on its corresponding camera pose and at least partly in reliance on some of the estimated three-dimensional ground point positions; and 
 merging the orthorectified detail images to create an orthomosaic of the survey area. 
 
     
     
         31 . The method of  claim 21 , wherein the number of detail cameras is two. 
     
     
         32 . The method of  claim 21 , wherein the number of detail cameras is four.