Real-time Spherical Map Correction for Wireless Devices
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Solution Overview
Problem
Existing map projection techniques, such as Mercator, are computationally intensive and unsuitable for small wireless handheld devices due to their limited processing capacity, leading to inefficient compensation for distortions in map projections at high latitudes.
Innovation Solution
A method is introduced that applies a simple spherical correction factor, calculated using the cosine of the absolute value of the latitude of the map's center, to correct map data displayed on wireless devices, which is computationally efficient and effective beyond a predetermined zoom level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Mercator projection is used to correct map distortions, then map accuracy is improved, but computational complexity increases making it unsuitable for handheld devices
Solution Approach 1:
The patent transforms the complex Mercator projection calculation into a simplified parameter-based correction system. Instead of calculating individual vertex corrections using full Mercator formulas, the system divides the map into latitude bands and applies pre-calculated scale factors based on the center latitude of each band. This parameter change from individual vertex correction to band-based scale factor application dramatically reduces computational complexity while maintaining acceptable accuracy for handheld devices.
Solution Approach 2:
The patent segments the map display area into multiple latitude bands, where each band receives a uniform scale correction based on its center latitude. This segmentation allows the complex continuous correction problem to be broken into discrete, manageable segments that can be processed efficiently on resource-constrained devices. Each band's correction is independent, further reducing computational overhead.
2Measurement precision
If computationally intensive map projection algorithms are applied, then distortion correction is improved, but processing time increases
Solution Approach 1:
The patent performs preliminary calculations of scale factors for different latitude bands and stores them in lookup tables before actual map display. When displaying a map, the system simply retrieves the appropriate pre-calculated scale factor based on the current view's latitude band, rather than computing the correction in real-time. This preliminary action eliminates repeated complex calculations and enables real-time display updates on handheld devices.
Solution Approach 2:
The patent creates simplified copies of the correction data in the form of pre-calculated scale factors stored in lookup tables. Instead of copying and executing the full Mercator projection algorithm repeatedly, the system copies only the essential correction parameters (scale factors for different latitude bands) and applies them directly during map display, significantly reducing processing time.
3Measurement precision
If spherical correction factor is applied to all vertices individually, then correction precision is improved, but computational load increases
Solution Approach 1:
The patent applies local quality by using the center latitude of each latitude band to determine the scale factor for all vertices within that band. Instead of applying a unique correction to every single vertex based on its exact latitude, the system applies a uniform correction characteristic to each band that locally approximates the true Mercator correction. This local quality approach maintains sufficient precision for each region while dramatically reducing the total computational load.
Data Source
AI summary
A method of displaying a map on a wireless communications device, the method comprising obtaining map data for rendering the map to be displayed on the wireless communications device and determining a zoom level of the map. If the zoom level of the map exceeds a predetermined zoom level, corrected map data is generated by applying a fixed spherical correction factor to the map data. If the zoom level of the map does not exceed the predetermined zoom level, the corrected map data is generated by computing a spherical correction factor based on a latitude of the map. The method also includes rendering the corrected map data to display the map on a display of the wireless communications device.