Claims
- 1. A method for determining the elevation of terrain features in synthetic aperture radar image data using two antennae spaced apart a fixed distance, B, on a platform which carries the radar over terrain at a known altitude, a, with respect to a fixed reference, where the distance B is measured in a horizontal plane while the platform is in level flight, comprising the steps of
- separately processing the return signals from said antennae to the pixel level and determining the slant range, R, and phase difference, .DELTA..phi., of pixels from the return signals received through said two antennae from substantially the same point of said terrain,
- from said phase difference, .DELTA..phi., and said spacing, B, determining for each pixel the slant angle, .theta., between the slant range and a vertical line from the radar platform to the terrain,
- determining the vertical height, h, of said platform above each pixel from the slant range R as a function of the cosine of the slant angle .phi. for each pixel, and
- for each pixel, determining elevation, a', above said fixed reference as the difference between said known altitude a of the radar platform and the determined height h of said platform with respect to a corresponding point on said terrain for each pixel.
- 2. A method as defined in claim 1 including the process of displaying said pixels with an indication of elevation.
- 3. A method as defined in claim 2 including the step of determining the horizontal distance, d, of each point on said terrain for each pixel from said vertical line and displaying each pixel at its distance from said vertical line.
- 4. A method as defined in claim 1 wherein said indication of elevation is displayed by quantizing elevation of pixels at predetermined constant intervals, and for pixels of equal quantized elevation, displaying intensity in a predetermined color distinct from all other colors used for other quantized elevations over at least a distinct band of quantized elevations.
- 5. A method as defined in claim 4 including the step of determining the horizontal distance, d, of each point on said terrain for each pixel from said vertical line and displaying each pixel at its distance from said vertical line.
- 6. A method for determining the elevation of terrain features in synthetic aperture radar image data using two antennae spaced apart a fixed distance, B, on a platform which carries the radar over terrain, where the distance B is measured in a horizontal plane while the platform is in level flight, comprising the step of
- separately processing the return signals from said antennae in complex vector form to the pixel level, and recording for each pixel from each antennae the altitude, a, of the radar platform above a fixed reference together with the roll angle, .alpha., of the platform,
- determining the slant range, R, of pixels from the return signals received through said two antennae from substantially the same point of said terrain,
- from said pixel data in complex vector form, determining the phase difference, .DELTA..phi., between pixels received from substantially the same point through said separate antennae from the relationship expressed by the equation .DELTA..phi.=(2.pi.B/.lambda.) sin (.theta.-.alpha.) where .lambda. is the wavelength of said radar,
- determining the vertical height, h, of said platform above each pixel from the slant range as a function of the cosine of the slant angle R for each pixel, and
- for each pixel, determining elevation, a', with respect to said fixed reference as the difference between said known altitude a of the radar platform and the determined height h of said platform with respect to a corresponding point on said terrain for each pixel.
- 7. A method as defined in claim 6 including the process of displaying said pixels with an indication of elevation.
- 8. A method as defined in claim 6 including the step of determining the horizontal distance, d, of each point on said terrain for each pixel from said vertical line and displaying each pixel at its distance from said vertical line.
- 9. A method as defined in claim 7 wherein said indication of elevation is displayed by quantizing elevation of pixels at predetermined constant intervals, and for pixels of equal quantized elevation, displaying intensity in a predetermined color distinct from all other colors used for other quantized elevations over at least a distinct band of quantized elevations.
- 10. A method as defined in claim 9 including the step of determining the horizontal distance, d, of each point on said terrain for each pixel from said vertical line and displaying each pixel at its distance from said interval.
ORIGIN OF INVENTION
The invention described herein was made in the performance of work under a NASA contract and is subject to the provisions of Section 305 of the National Aeronautics and Space Act of 1958, Public Law 85-586 (72 Stat. 435; 42 USC 2457).
US Referenced Citations (23)
Non-Patent Literature Citations (1)
Entry |
"Two Frequency Radar Interferometry Applied to the Measurement of Ocean Wave Height," IEEE Transactons on Antennas and Propagation, vol. AP-21, No. 5, Sep. 1973, pp. 649-656. |