John
I've added the metapost code from http://therion.speleo.sk/wiki/doku.php?id=metapost and it plots the whole line rather than just the ends.
From my understanding it seems like your metapost code is working as intended. It changes the symbol used for plotting, not what is plotted.
I've tried adding thee names of surveys which are not in the scraps to the map, but no centreline is shown. ... Is there a way to just get all the centreline plotted?
I have little experience with extended elevations (which I expect are a little more complicated than plans and projected elevations). The following (plan) map definitions indicate the approach I take, and it usually works for plan and projected elevations. I separate out maps composed of scraps and maps composed of surveys. (My survey in this example is called ro) All of the survey maps can then be collected together into a master 'survey centreline' of the whole cave (separate to the drawings). When you come to compile a drawing, select both the 'map of scraps' and the 'map of survey centrelines' for plotting both. Sometimes I have problems if I have symbol-hide group cave-centerline or something similar set by accident in a layout somewhere. Of course there will be nothing to plot! Also if your drawings are opaque and the survey is plotted on the bottom, it will be hidden. In th example below s6 plots on top of s1 and s2. Example of the first bit of this process; map Late08ROPlan -title "Late08 RO Plan" \ -projection plan Late08ROPlan_s6 #passage that ducks under White River break Late08ROPlan_s1 #Page 3 Passage Late08ROPlan_s2 endmap map Late08ROPlanCL -title "Late08 RO Plan (centreline)" \ -projection plan ro endmap Also extended elevations require careful use of the extend statement. For example, this statement extend ignore 1 5 would in effect hide the survey legs between station 1 to 5, for example. Not sure if any of this will help, but it outlines some issues I had when getting going. Bruce