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How does MacENC compute true wind info from the apparent wind info it gets from my Navman 3150 wind indicator? That unit sends out NMEA ($IIVWR,001,L,6.79,N,3.49,M,12.58,K and $IIMWV,000,R,6.79,N,A)
which is the apparent version, with reference to the boat heading (0 degrees). The instrument itself also displays "true" wind info if it receives the boat speed (I give it the RMC sentence that contains SOG). But doesn't this assume that the boat is actually going in the same direction as it is pointed (i.e. its "heading")? That is a good approximation, but does not account for cross currents or leeway. Shouldn't we use the GPS COG as the reference, which is the actual direction the boat is moving relative to the earth?
I'm not sure about this, because apparent wind direction relative to the boat is obviously useful for sail trim. But to estimate one's speed upwind (for example) it would seem to be important to relate wind info to the actual movement of the boat relative to earth. That should be easy by using COG from the GPS. Does anyone do that?
BTW, there is a good description of the trig needed to convert apparent to true wind info on the US Sailing website (http://www.sailingcourse.com/keelboat/tr...ulator.htm) if anyone needs a refresher (I did).
I got into this playing with an Arduino computer connected to a GPS source and a tilt-compensated magnetometer to measure the ship's heading, but then realized I didn't understand whether to use COG or not.
Comments are very welcome.

Hi!

we are sail with MacENC and iNavx more than 10000 miles, and generally very happy :-)

But, one small problem could be some time BIG :-)

I saw this problem only when MacENC managed GPS position, but with 3 different Mac and 4 different GPS (including Garmin) connected over USB, NMEA or Bluetooth ...

what's happens - some time (look at the first picture) - position for 1-2 seconds move in any direction, it could be from 10 to 500 miles.

[image]http://www.sailblogs.com/sbgallery/pics/v_apukov_gmail_com/sbdukb8ts/sbd4jkdda/w/sbp2dpt9.jpg[/image]

minor problem - your tracking data about distance, speed and etc wrong.

but!!! last trip - we found force 9 storm with gusts more than 50knt, with 2 different, in-depended forecast 20-25knt!!! :-)

[image]http://www.sailblogs.com/sbgallery/pics/v_apukov_gmail_com/sbdukb8ts/sbd4jkdda/w/sb9mpak5.jpg[/image]

We found it on big sail, and can't furl it back! we have just one choice - turn downwind and pray :-) 9 hours until wind slow down and change direction.

unfortunately on the our way - traffic separation scheme with lot of ships. at this moment understanding information from AIS - VERY important ... but if exactly at this moment You position moved to centre of Sakhara ... You are in big trouble :-)

May be somebody saw similar problem?

Hi, I know that the display can be changed to disable the location services when there is NMEA data coming in on WiFi. However when I take this along with my BT GPS to smaller boats without NMEA WiFi, I would like the internal compass turned off and just to use the BT data. Is this feasible? Thanks, Joel

How about adding an in-app purchase option and writing a layer that could display XM Weather? Currently I am using Foreflight and toggling back and forth to see weather that coming when out of cellular range (usually when in range as well, it is just easier). Yes, the XM subscription is a bit much as well as the hardware to get it, but when you are out of range of a cell tower, it is nice to know what is coming at you. It would be really great to have that overlaid in iNavX. Am I the only one that sails outside of cell range? I looked at the Theyr, but as far as I can tell, it is dependent on cell towers and loops the radar? Thanks, Joel

What are these squares and how to remove them?

[image]http://habrastorage.org/storage3/f56/043/237/f560432374911656504d2e707da1ea73.png[/image]

NZ Linz update in the Marine GeoGarage

14 charts have been updated in the Marine GeoGarage
1 chart (NZ2681 Plans in the Chatham Islands) has been permanently withdrawn

US NOAA update in the Marine GeoGarage

15 charts updated + 1 new chart for St Mary's River

I am using iNavX on my iPad mini for over a year. My iPad is Wifi version and get GPS signal via external GPS receiver through Bluetooth. It is no problem before. But after I upgraded the iNavX to Version 3.7.5 on 9 Jan, problem appear. It seems running but very slow response. It reacts to the command after a few seconds (4-10 seconds). Please advise what is going wrong.

Remarks: My iPad 2 running fine after upgrade the iNavx Version 3.7.5

Anyone know the best way to transfer waypoints and routes from MacENC to B&G zeus touch8 mfd. I do have a navico gofree wifi which connects the zeus to MacENC via TCP and supplies 0183 data.

http://noaacoastsurvey.wordpress.com/201...g-systems/