Surfer 13 and subsequent versions do not resample the imagery during import. You can load the entire SID or ECW file, or even extract a portion of the file to import, at the original resolution.
Surfer 12 and previous versions resampled ECW or SID images during import. To save on loading and processing time, it was necessary to design Surfer 12 (and previous) to automatically reduce the resolution of very large ECW or SID files, even when choosing a Pixel Reduction of 1/1 during import. If the ECW or SID file is larger than 8192 x 8192 pixels, then Surfer will automatically scale it down by halving the number of pixels until the largest dimension is under 8192 pixels.
For example, your ECW or SID file is 28000 x 14000 pixels. Divide that in half to get 14000 x 7000 pixels. Since the largest dimension is still over 8192 pixels, divide it again to get the pixel dimensions of 7000 x 3500 pixels (with a Pixel Reduction of 1/1). That is quite a significant reduction in resolution for the image.
Updated October 20, 2017