Bob Thrun wrote:Luc Le Blanc speaks of "splay measures". After carefully reading his messages, I am not sure just what he means by that term. Apparently it implies special handling of splay shots, instead of just treating them as survey shots.
Bob is correct, and this must be the source of confusion: I use the words "splay measures" to differentiate them from ordinary survey shots between stations. Splay measures are just measures (...) taken between a survey station and some arbitrary non-station points (a rock, a formation, an angle in the wall, etc.) that only serve to display lines on the line plot to help with sketching. When done with sketching, these lines can be hidden without affecting the line plot (other than uncluttering it). These measures don't add up to cave development and don't create survey stations. View them as sophisticated LRUDs (left, right, up and down) measures, where headings and slopes are kept, not just their length. They can also be used to measure a cross-section, best done with a DistoX rotated perpendicular along the axis formed by a survey shot that follows the cave passage, so as to measure a "slice" of that passage; by acquiring several such measures, it's possible to get a refined view of the passage section, as if working with a point cloud mapper.
What is the benefit of preferring splay measures over splay shots? They:
* don't clutter the line plot with a bunch of lines only aimed at sketching (even worse if station numbers are displayed too!)
* dont' count in cave development and statistics
* don't mess the graph of passage trends (like Compass' rose diagram)
* don't use up station numbers
* don't extend the list of survey stations (requires more memory, takes longer to find a path)
* don't require marking additional stations (where this is standard practice)
* don't require backsights (where this is standard practice)
Auriga offers to qualify splay measures as pointing towards a wall, the floor/ceiling or some detail (ex. a rock in the middle of a room). This way, it knows whether or not to join these measures to the wall outline in top and profile views. Therion differentiates between detail and floor/ceiling/wall splay measures. As for PocketTopo, I'm not sure it differentiates whether splay measures reach a wall or not, they just appear in the list as shots between a survey station and nothing (end station field left empty).
If you just want to take a bunch of regular survey shots in a splay manner, i.e. regular survey shots between proper survey stations that just break the usual sequential numbering of stations, yes, I assume any software can do that. You just have to override the automatic incrementation of station numbering.
Ex. instead of going
1->2
2->3
3->4
you do
1->2
1->3
1->4
I hope this clarifies things.