Full Description of Compass Release with SVG Round Tripping

Techniques, equipment and issues. Also visit the NSS Survey & Cartography Section.

Moderator: Moderators

Full Description of Compass Release with SVG Round Tripping

Postby elfish » Mar 28, 2010 6:08 pm

I wanted to announce a major New Release of Compass. You can get copies of the new version here:


The release contains a number of important changes and improvements:

I. Cartography Tools. The Compass Cartography Tools are a new set of programs that helps you create presentation-quality digital survey map from Compass files.

A. SVG Exporter. SVG is a widely used file format for drawing programs. Because it is so widely used, it is an ideal format for exporting cave data. For example, programs like Adobe Illustrator and Corel Draw will read and write these files. Even more important there are Freeware programs like Inkscape that can read and write SVG files. The SVG Exporter allows you to export cave survey data as SVG files. The SVG files contain a complete cave map on multiple "layers" that include stations, shots, passages, LRUD marks, a grid, a north arrow, a scale bar, a frame, and a colored background. The exported map also contains empty layers into which you can place your hand-drawn passage walls, floor details, a legend, notes, etc. This allows you to use the SVG map as the starting point for a high quality, finished digital map.

B. Merge/Morph Tool (Round-tripping). This tool solves one of the biggest problems for cave cartographers: updating an existing map as the data changes. For example, if you survey a new passage, the new data will need to be added to the existing map. If the passage is extensive, you may have to reduce the scale, use bigger paper or even rotate the cave so everything fits on a piece of paper. In addition to adding new data, you may correct errors in the data or improve the loop closure. When this happens, all the shots in the cave may move. This may change the angle that shots come together and passage intersect. When this happens all the carefully drawn wall details will need to be moved, stretched, compressed or warped to match the new shot position. Normally these kinds of changes would require lots of painful and tedious hand adjusting. If the changes are extensive enough, it may even require starting a new map from scratch.

The Merge/Morph tool allows any SVG-based map to be adjusted even after passage lines have been drawn, floor detail placed and the map has been finished. It allows you to move, rotate and scale all the hand-drawn elements of a finished cave map, so the map can be completely re-configured without losing any of the hand-work in the map. The tool will also smoothly warp (morph) the passage walls, floor details and other hand-drawn elements so they track changes in the shot positions. For example, if the angle at a passage junction becomes tighter, the passage walls will be compressed to fit and still maintain the same relative distances from the shot lines.

C. Converting And Adopting. The SVG Converter has special tools that allow you to use maps that were generated with different drawing programs. For example, Inkscape has different layering system than Adobe Illustrator so Illustrator layers do not show up in Inkscape. In addition, programs like the Compass SVG Exporter and Walls, require certain layers to be in place before they can be merged, morphed, or round tripped. The SVG Exporter can add these layers to any SVG file, whether it was originally generated by a cave survey program or not. As a result, the SVG Exporter can "adopt" an existing cave map even if it wasn't originally generated by Compass or Walls. Once the map has been "adopted," it can be treated just like a map that was generated by Compass or Walls. In other words, It can be merged, morphed or round tripped.

D. Using Inkscape. One of the big advantages of SVG is the fact that there are several Freeware drawing programs that support it. One of the best is Inkscape, a drawing program that is very similar to Adobe Illustrator. Since Illustrator can costs hundreds of dollars, Inkscape is a perfect alternative for cavers on a budget.

Because Inkscape is free and works well for cave mapping, I have developed the Exporter to be compatible with Inkscape. (It will also work fine with other programs such as Illustrator.) Because all sophisticated drawing programs require a lot work to learn, I have designed a detail tutorial on making cave maps using Compass and Inkscape.

II. Sketch Map Editor. The Sketch Map Editor helps you to take the sketch maps you generate in the cave and use them as the basis for your finished maps. The Editor allows you to edit a scanned bitmap image and remove flaws, align it to north, scale it to a standard scale, and trim the image to size. It also allows you to merge multiple images into a single image, using transparency to precisely align the passages. Finally, it allows you to warp or "morph" the image so station-positions in the sketch map precisely match the positions in the cave data. Once a combined image has been created in the Editor, the image can be loaded into a drawing program for tracing. Having a precisely aligned, single image makes producing a map much quicker and easier because you don't have to load and align individual images. Also, since the image has been warped to match the survey shots, you don't have to constantly shift the image as you are tracing.

III. Showing Loops. The Viewer now allows you to select loops and highlight them in the display. You can choose to highlight one or more loops at the same time. The loops can be "natural loops" which are the first loops in the sequence of surveying. They can also be optimized loops, which are loops with the smallest total length.

IV. Station Coordinates: You now have the option of displaying station coordinates next to each station. The coordinates can be displayed as UTM (Feet or Meters) or Longitude and Latitude in degrees or degrees minutes and seconds.

V. Zone Crossing. In some rare instances, you may have two or more caves that aren't in the same UTM zones. This usually occurs when you have a cave system close to the Zone boundary. Compass now allows you to handle that situation by extending the base zone so it encompasses the caves beyond it. This is standard practices in cartography.

Infrequent Poster
Posts: 4
Joined: Nov 28, 2009 10:48 pm
NSS #: 20617
Primary Grotto Affiliation: Colorado Grotto

Return to Survey and Cartography Forum

Who is online

Users browsing this forum: No registered users