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hi youtubers jeff cote here with  ask pys we've got a question from a  fellow voter  cheryl asks a really good question by  the way um  common question that i get and this is  all  about details right here so listen in on  this one this one is good  what is the difference between a heading  sensor and a gps  should i have both on my boat we like to  anchor and we'll be traveling to alaska  next summer  okay this is a good one i like it  so gps is  provides a value called course on ground  that is basically effectively where your  boat is  traveling to not where your boat is  heading and if that's confusing  hang on and let me demystify all this  so the reality is that our boats  are traveling in a direction with the  sum  of different forces acting upon our  boats  so what are those forces well one of  them is propulsion so  propulsion could be from your engine or  from your sails  right and so with that you're moving in  a given direction  the next is tide or current there are  the reality is there are tides and  currents in this world and the slower  your  boat moves those currents like here in  the pacific northwest can be two knots  three knots  those currents affect where your boat is  going to go even if you don't have wind  or propulsion your boat is actually  moving at two to three knots  wherever the current or the tide is  bringing you to right  and then the other part that's also  really interesting is you also have wind  so you've got wind pushing you somewhere  you've got tide  which effectually affects currents and  then you also have propulsion which is  either your own the motor or wind  and so in the pacific northwest and a  lot of places on earth you  actually rarely go where you're actually  pointing  and the that's confusing yeah you're  actually not going where you're pointing  your boat  so where the boat is heading is actually  different than where it's going  and those two vectors and if you enable  them on your chart plotter you can  actually if you have an autopilot  you have by default a heading sensor and  the heading sensor is going to be  directly obviously  facing the bow of your boat but your  course on ground might be like this  so you're going to have a delta between  what you're where you're going  and with your boat and where you're  heading or where you're heading with  your boat  and where you're going with your gps and  the delta between those is course on  ground via heading  and the reason why heading is really  important is if you ever want to do a  chart overlay or radar overlay onto a  chart  the radar overlay is going to be skewed  if your boat heading  is not included or not part of the chart  plotter  because the radar overlay won't  understand that you're actually not  going  where you're pointing and so with a  heading sensor connected to a chart  plotter  your ar overlay is going to be perfectly  synced  some radar manufacturers actually don't  allow radar overlay  unless you have a heading sensor so  simply you cannot do radar overlay  without a heading sensor  garmin makes budget heading sensors and  there are more expensive heading sensors  that are sort of built with  autopilots if you have an autopilot you  either have a fluxgate compass which is  a heading sensor  or it's going to be a digital gyro  heading sensor  and you're going to also be able to know  where your boat is actually pointing to  as opposed to where it's going  so the question by cheryl was do i  should i have both  and my answer is most definitely you  should have a heading sensor on your  boat  and you should have obviously a gps with  course overground  thank you for watching this video if  you've got further questions  and you're wondering about your own boat  please ask questions below or send us an  email with your questions and we'll get  to them  hopefully as soon as possible if you haven't done so please subscribe  to our youtube and get our weekly  updates we're posting about four videos  a week right now  and also thanks for watching