Geoinformatics FCE CTU (Jul 2018)
Plotting the map projection graticule involving discontinuities based on combined sampling
Abstract
This article presents new algorithm for interval plotting theprojection graticule on the interval $\varOmega=\varOmega_{\varphi}\times\varOmega_{\lambda}$based on the combined sampling technique. The proposed method synthesizesuniform and adaptive sampling approaches and treats discontinuitiesof the coordinate functions $F,G$. A full set of the projection constantvalues represented by the projection pole $K=[\varphi_{k},\lambda_{k}]$,two standard parallels $\varphi_{1},\varphi_{2}$ and the centralmeridian shift $\lambda_{0}^{\prime}$ are supported. In accordancewith the discontinuity direction it utilizes a subdivision of thegiven latitude/longitude intervals $\varOmega_{\varphi}=[\underline{\varphi},\overline{\varphi}]$,$\varOmega_{\lambda}=[\underline{\lambda},\overline{\lambda}]$ tothe set of disjoint subintervals $\varOmega_{k,\varphi}^{g},$$\varOmega_{k,\lambda}^{g}$forming tiles without internal singularities, containing only ``good''data; their parameters can be easily adjusted. Each graticule tileborders generated over $\varOmega_{k}^{g}=\varOmega_{k,\varphi}^{g}\times\varOmega_{k,\lambda}^{g}$run along singularities. For combined sampling with the given threshold$\overline{\alpha}$ between adjacent segments of the polygonal approximationthe recursive approach has been used; meridian/parallel offsets are$\Delta\varphi,\Delta\lambda$. Finally, several tests of the proposedalgorithms are involved.
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