SEGYImport performance
Small performance improvements in SEGYImport: 1) Only call CalculateGatherSpacing when importing 4D data. 2) Use std::unordered_map instead of std::map.
Small performance improvements in SEGYImport: 1) Only call CalculateGatherSpacing when importing 4D data. 2) Use std::unordered_map instead of std::map.