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The Sketch Editor is designed to help you process your sketch-maps for easier use. The program will scale, combine and adjust the images so the match the survey data precisely. This makes it much easier to produce finished maps. This section gives you a general overview of the process. For a step-by-step tutorial, with examples from a real cave, refer to the Tutorial Section. The process is done using three steps:
1. Editing. In this step, you scale the scanned sketch-maps so they have a consistent resolution and they match the scale used by the sketch-mapper. You also trim the image so that only the relevant parts of the sketch remain. Next, you flip the image so that north corresponds to the top of the image. Finally, you de-rotate the image to remove small rotations that were introduced during scanning.
You also have the opportunity to cleanup the image. You can improve the image quality by adjusting the contrast, brightness and gamma. You can fill the background with a uniform color to improve the clarity of the image. You can even draw on the image to fill in weak or missing lines. Finally, you can erase irrelevant data, smudge marks and other defects.
This step assures that each sketch-map is uniformly scaled and rotated and will match the other images in the survey. Uniform scaling allows the images to be combined with minimal adjustment, distortion or fudging.
2. Morphing. The Morphing process mathematically adjusts the image to correct for errors in positions of the survey stations in the sketch. It uses the Beiers-Neeley algorithm which is the standard method for morphing images (http://www.hammerhead.com/thad/morph.html). In addition to moving the stations, the algorithm moves the pixels near the stations so the passage walls and floor detail are adjusted too. The affect trails off with distance so the parts of the image that are far from the error are not moved. This gives smooth warping effect almost like the sketch maps had been draw on rubber and stretch to the proper position.
The morphing process is usually done on each individual image to correct for local errors. Then, once the images have been combined, the whole sketch-map is warped to remove any residual errors. This results in a map with minimum distortion.
3. Combining. The final step in the process is combining multiple sketches into a single image. During this part of the operation, you can rotate and resize each sketch so they fit together perfectly. The images can be made transparent so it is easy to see all the passage lines and marks and how they will fit together.
Once the sketches have been combines and edited, they can be loaded into a drawing program such as Adobe Illustrator or Inkscape and used to trace the passage outlines. Because the images have been to edited to exactly match the line plot, the tracing produced in a drawing program will match the actual line plots.