Cave Surveying Group Therion and DistoX Training Course Guide Comprehensive instructions and sample data for you to practise with.

Marco Corvi Effective DistoX with TopoDroid Improper use of the DistoX can lead to gross mistakes. This work reviews examples of bad usage of the DistoX and the functions provided by TopoDroid to avoid them.

• Remember that each button has at least two functions, one when it is pressed for a short time only, the other when it is pressed and held.
• DistoX1: Taking shots requires that the DIST button be pressed and released straight away. This is a silent process. Only after the distoX1 has determined the success or failure of the shot will a sound be made.
• DistoX2 will work as above, but it is better to press+hold the DIST button, as you are less likely to shake the device right when it is trying to stabilise the sensors for measurement.
• The above is almost impossible while wearing gloves and with the DistoX in a case or transparent drybag. Solutions are; a self adhesive raised dot on the DIST button, or put a rubber band around the distoX over top of the DIST button, so you can locate the button by touch.

This next bit does depend on your preferred workflow, and on the settings, or 'Stations Policy' you have set in the sketching application you are using. It was originally written for PocketTopo, and is just one of a number of ways it could be done. It matches a TopoDroid survey data 'Stations Policy' setting of “Splays, forward legs”

• When arriving at a station take all the splay shots (what used to be LRUD) BEFORE taking shots to the next station. Make sure the pda/person booking has recorded points and knows what they are after every 2 or 3 splay shots BEFORE taking any more shots.

• When taking shots, imagine you are the pda operator trying to progress the drawing based on what you have already done. For large passages, chambers or wherever you are inspired to collect lots of detail, this might be something like;

1. define cross section It it important to do it first, because all measured splay shots will define only the cross-section and nothing else. It prevent you from mess if too many splay shots was measured before. Ie for a quadrilateral section shape, this would be the four corners. For an arbitrary shape take maybe 8 shots around the passage section. (The 'to station' for these shots would be a - (a dash) for wall shapes and . (a dot) for “in cave” features (blocks, pits, chimneys, …) for in Therion)
2. define passage plan shape generally along the line where the floor meets the wall generally in the direction the survey is proceeding. This could extend to picking up the ceiling if it is significantly different to the floor. (The 'to station' for these shots would be a - (a dash) in Therion – when implemented)
3. define important plan features (edge of water, pits, speleothems, rigging or large rocks etc). (The 'to station' for these shots shots would be a . ( a dot) in Therion– when implemented)
4. define passage extended elevation shape (long section) shape. Pick up general changes in floor and ceiling gradient or steps from the previous station towards the next station (unless already picked up). (The 'to station' for these shots would be a - (a dash) in Therion – when implemented)
5. define important extended elevation features (ledges, pits, speleothems, rigging or large rocks etc). (The 'to station' for these shots shots would be a . ( a dot) in Therion– when implemented)

• For smaller or relatively featureless passages the process can be simplified.
• Three (successful) shots to the same place means it's a survey leg, and the pda assumes you will now move to that place.