Systems and methods for multispectral landscape mapping
Image acquisition and analysis systems for efficiently generating high resolution geo-referenced spectral imagery of a region of interest. In some examples, aerial spectral imaging systems for remote sensing of a geographic region, such as a vegetative landscape are disclosed for monitoring the development and health of the vegetative landscape. In some examples photogrammetry processes are applied to a first set of image frames captured with a first image sensor having a first field of view to generate external orientation data and surface elevation data and the generated external orientation data is translated into external orientation data for other image sensors co-located on the same apparatus for generating geo-referenced images of images captured by the one or more other image sensors.
1. A non-transitory computer-readable storage medium containing machine-executable instructions for performing a method of generating geo-referenced spectral images of a landscape from a first plurality of images captured by a first image sensor of an aerial platform and a plurality of spectral images captured by a multispectral (MS) image sensor of the aerial platform, wherein the method comprising:
performing an aerial triangulation and bundle adjustment process on the first plurality of images to determine first image sensor external orientation (EO) data, the first image sensor EO data defining the EO of the first image sensor when each of the first plurality of images was captured by the first image sensor;
generating a digital elevation product from the plurality of first images and the first image sensor EO data; and
orthorectifying at least one of the plurality of spectral images according to the digital elevation product.
2. The non-transitory computer-readable storage medium of claim 1 , wherein the method further comprises:
co-registering the spectral images with corresponding ones of the first plurality of images;
wherein the step of orthorectifying includes orthorectifying at least one of the plurality of spectral images according to the digital elevation product and the first image sensor EO data.
3. The non-transitory computer-readable storage medium of claim 2 , wherein the step of co-registering includes:
identifying, in the first plurality of images, a plurality of tie points;
identifying, in corresponding ones of the plurality of spectral images, pixels that correspond to the identified plurality of tie points; and
resampling one or more of the plurality of spectral images according to the tie points to co-register each of the plurality of spectral images with corresponding ones of the first plurality of images.
4. The non-transitory computer-readable storage medium of claim 1 , wherein the method further comprises:
calculating MS image sensor EO data from the first image sensor EO data;
wherein the step of orthorectifying includes orthorectifying at least one of the plurality of spectral images according to the digital elevation product and the MS image sensor EO data.
5. The non-transitory computer-readable storage medium of claim 4 , wherein the step of calculating MS image sensor EO data from the first image sensor EO data includes translating the first image sensor EO data to the MS image sensor EO data according to one or more camera rig parameters.
6. The non-transitory computer-readable storage medium of claim 5 , wherein the camera rig parameters include at least one of internal orientation (IO) data for the first image sensor, IO data for the MS image sensor, and relative spatial positioning information for the first image sensor and MS image sensor on the aerial platform.
7. The non-transitory computer-readable storage medium of claim 1 , wherein the MS image sensor is configured to simultaneously capture a plurality of spectral images at a plurality of corresponding spectral bands, the plurality of MS images including a plurality of spectral images at each of the spectral bands, and the method further comprising co-registering the images of the plurality of spectral bands.
8. The non-transitory computer-readable storage medium of claim 1 , wherein the first plurality of images and the plurality of spectral images were sequentially captured during a flight path of the aerial platform over the landscape by sequentially triggering the first image sensor and MS image sensor at the same time.
9. The non-transitory computer-readable storage medium of claim 1 , wherein the first plurality of images overlap by at least 50% in at least one direction and wherein the plurality of spectral images overlap by less than 40% in at least one direction.
10. The non-transitory computer-readable storage medium of claim 1 , wherein the first plurality of images overlap by at least 70% in a lateral direction and the plurality of spectral images overlap by less than 40% in the lateral direction, wherein the lateral direction is orthogonal to a flight path direction of the aerial platform when the first plurality of images and plurality of spectral images were captured.
11. The non-transitory computer-readable storage medium of claim 1 , wherein the digital elevation product is a digital surface model.
12. The non-transitory computer-readable storage medium of claim 1 , wherein the method further comprises generating a mosaic of the orthorectified spectral images.
13. The non-transitory computer-readable storage medium of claim 1 , wherein the first image sensor is a panchromatic camera and the MS image sensor includes at least three spectral bands.
14. The non-transitory computer-readable storage medium of claim 1 , wherein the landscape is a terrestrial landscape including one or more of a vegetative landscape, an agricultural landscape, an ocean, a lake, an estuary, a stream, a river, an inland sea, a wetland, a coastal region, an urban landscape, a suburban landscape, a rural landscape, an industrial landscape, a glacier, or an ice sheet or an extraterrestrial landscape.
15. A non-transitory computer-readable storage medium containing machine-executable instructions for performing a method of generating a flight plan that includes a flight path and a series of image capture locations for an aerial system, wherein the aerial imaging system includes a first downward-looking camera that is a panchromatic camera and at least one second downward-looking camera that includes a multispectral camera, wherein the field of view of the first camera has a cross-sectional area between at least 50% greater than and at least 100% greater than a cross-section area of the field of view of the second camera, wherein the field of view of the second camera is centered within the field of view of the first camera, and wherein the first and second cameras are triggered at the same time and have the same frame rate such that multispectral digital images of a given portion of the landscape taken by the second (multispectral) camera each reside within a panchromatic digital image of the corresponding portion of the landscape taken by the first camera, wherein the method of generating the flight plan comprises:
ensuring a sufficient number of images are captured so that a continuous map of the landscape can be generated and so that the image capture locations result in an overlap of adjacent images, including a longitudinal overlap in the flight path direction and a lateral overlap in the lateral direction; wherein:
the lateral overlap of adjacent panchromatic images is in the range of 30% to 90% and the lateral overlap of adjacent multispectral images is in the range of 20% to 50%; and
the longitudinal overlap of adjacent panchromatic images is in the range of 30% to greater than 70% and the longitudinal overlap of adjacent multispectral images is in the range of 20% to less than 50%.
16. The non-transitory computer-readable storage medium of claim 15 , wherein the specified longitudinal overlap of the series of images may be obtained by varying the frame rate or the rate at which the cameras are triggered to capture an image.
17. The non-transitory computer-readable storage medium of claim 15 , wherein the specified longitudinal overlap of the series of images may be obtained by varying the speed of the aerial vehicle.
18. The non-transitory computer-readable storage medium of claim 15 , wherein the at least one second camera includes a thermal infrared camera.
19. The non-transitory computer-readable storage medium of claim 15 , wherein the machine-executable instructions for performing the method of generating a flight plan may be executed by a ground control station or a ground control module.
20. The non-transitory computer-readable storage medium of claim 15 , wherein the machine-executable instructions are executable by aerial vehicle electronics.