Best practice is to approach the line on close hauled, with bow calling the cross.
So, assume settings in EXP have the GPS at the stern (lets say 16m from the bow). So when the mark is pinged its at the bow - 16m further forward at the current HDG (or COG)?
Once both marks are pinged, then I assume EXP calculates the 'distance to the line' as the distance straight ahead, not perpendicular to the line - is it based on HDG or COG?
Would be grateful to understand the inputs and geometry for peace of mind please

I have both log files and 'cleaned' log file reports (with constant phases extracted using Tools).
What is the best way to overlay this data and see how close the actuals are with the polars?

I have just finished 4 long races on a wet TP52, including S2H22. Toughbook downstairs and ipads in waterproof case upstairs running Remote Desktop over WiFi (with one on charge downstairs and the other in use on deck). I have also used Mesa2 and 3.
1. iPad lasts about 4hrs, but you have to turn the screen way down in brighness and turn it off when not using
2. iPad daylight vision is poor
3. Water, spray, rain and oil in your fingers kills the iPad screen - its like a million fingers trying to do something all at once. I have a microfibre cloth during day races and a chamois for when it gets a bit wetter, but when its tough going its almost impossible - dry with a chamois and you leave a thin film of water and that kills the screen as well.
4. I have tried the Mesa's but the OS is a a bit clunky and they are a bit too small for me. There is a PRO coming out and they are aiming for IP67, but not there yet (not to mention the price)
5. I do use a stylus at times, but when the screen gets wet its not good.

I am looking for a way to use the iPad in the wet (hyrdophobic/phylic film), stylus only (havent cracked that one yet), apple pencil, other brnads (GETAC, etc)?

Anyone got the answer?

Just had a laptop/mouse failure due to being splashed (actually drowned) downstairs! 
Q1. Can anyone recommend a waterproof trackball?
Also we have Toughbook at nav station and Laptop (Remote desktop) and Mesa.
Q2. Could an expert explain the setup for using Toughbook (slave) and Mesa ondeck please.

Yep - cant seem to make the boxes simply autohide - have to close them and reopen?