Polar Projection Image Reprojection Using Variable Resolution Regions
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Solution Overview
Problem
Polar projections in geographic information systems (GIS) often result in highly distorted imagery due to area stretching, making reprojection challenging, especially for areas away from the pole.
Innovation Solution
The approach involves dividing a geographic area into image regions and using higher resolution imagery for areas farther from the pole, projecting image tiles at different scales rather than a single source image, to reduce distortion in polar projections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single source image is used for polar projection, then the reprojection process is simple, but the output image suffers from high distortion and stretching
Solution Approach 1:
The patent divides the geographic area into multiple image regions (e.g., northern, central, southern regions) and processes each region separately with appropriate resolution. This segmentation allows different parts of the map to use different source image resolutions, reducing overall distortion while maintaining manageable processing complexity.
Solution Approach 2:
The patent applies local quality by using higher resolution source images for regions farther from the pole where distortion is greater, and lower resolution for regions closer to the pole. This ensures that each local region receives the appropriate image quality needed to minimize distortion, with the equatorial regions receiving the highest resolution imagery.
2Manufacturing precision
If higher resolution imagery is used for all regions, then projection accuracy improves, but data processing complexity and resource requirements increase
Solution Approach 1:
The patent implements local quality by assigning different resolution levels to different geographic regions based on their distance from the pole. Regions experiencing greater distortion (farther from the pole) receive higher resolution imagery, while regions with less distortion receive lower resolution imagery, optimizing processing efficiency while maintaining accuracy where needed.
Solution Approach 2:
The patent changes the resolution parameter of source images based on geographic location. By dynamically adjusting the resolution parameter according to the region's distance from the pole, the system achieves optimal projection accuracy without uniformly processing all regions at maximum resolution, thus reducing overall computational complexity.
3Productivity
If uniform resolution is applied to all image regions, then processing is efficient, but distortion compensation is insufficient for polar projections
Solution Approach 1:
The patent applies local quality by using non-uniform resolution across different image regions. Each region's source image resolution is selected based on its specific distortion characteristics, with equatorial regions receiving higher resolution to compensate for greater stretching, while polar regions use lower resolution. This approach maintains processing efficiency while significantly improving distortion compensation.
Solution Approach 2:
The patent changes the resolution parameter of source images based on geographic location and distortion characteristics. By adjusting this parameter dynamically for each region rather than applying a uniform value, the system achieves both acceptable processing efficiency and improved distortion compensation tailored to each region's specific needs.
Data Source
AI summary
Embodiments relate to converting imagery to a polar projection. Initially, a map request that specifies the polar projection for a geographic area is obtained. The geographic area into a number of image regions. A first source image is obtained for a first image region, where the first source image is at a first target resolution, and a second source image is obtained for a second image region, where the second source image is at a second target resolution that is determined based on a geographic location of the second image region. The first source image and the second source image are projected into the polar projection to obtain a single output image. At this stage, a polar coordinate system that corresponds to the polar projection is used to render the single output image in a spatial map.