PolarView NS 1.9.6 / PolarCOM 1.9.6

PolarView NS
- Fixes and improvements to vector chart rendering
- Fix ActiveCaptain POI display

PolarCOM
- Fixes for Actisense NMEA 2000 processing

PolarView NS 1.9 / PolarCOM 1.9

PolarView NS
- Download of NOAA raster charts
- Option to drop waypoint at vessel location by pressing ‘Shift’
- Numerous miscellaneous bug fixes and improvements

PolarCOM
- Support for SeaSmart and Actisense NMEA 2000 gateways
- Numerous miscellaneous bug fixes and improvements

Route & Waypoint manager will now require an activated copy of PolarView NS after free trial period.

Release 1.6 is updated

PolarView release 1.6 has been updated to fix a few minor bugs. The current PolarView version is 1.6.3.

PolarCOM release 1.6 has been updated. This update adds an option to send NMEA data over UDP, including support for UDP broadcast. The current PolarCOM release is 1.6.20

Navigation / Instrument Acronyms

Since users ask about these from time to time, here is the list of acronyms used to denote certain navigation related data items in PolarCOM instruments and elsewhere:

POS – position, that was easy
SOG – speed over ground. Speed of a vessel relative to stationary land.
COG – course over ground. Course of a vessel relative to stationary land.
VTW – speed (velocity) through water. Speed of a vessel relative to water.
HDG – heading. Compass direction into which the bow of a vessel is pointing.
DBK – depth below keel. Water depth measured from bottom of keel
DBS – depth below surface. Water depth measured from surface of water or vessel waterline.
DBT – depth below transducer. Depth as returned by transducer, unadjusted.
AWA – apparent wind angle. Angle of apparent wind as seen from a moving vessel, relative to vessel bow-stern axis.
TWA – true wind angle. Angle of true wind relative to vessel bow-stern axis.
TWD – true wind direction. Compass direction from which the true wind is coming.

VMG – speed (velocity) made good. Speed with which a vessel is moving towards its destination, as measured on a line between current vessel position and destination.
XTE – cross track error. In general, shortest distance from current vessel position to the nearby route leg.
BTN – bearing to next. Compass bearing to the next waypoint enroute.
DTN – distance to next. Distance to the next waypoint enroute.
ETEN – estimated time enroute to next.
ETAN – estimated time of arrival to next.
DTD – distance to destination. Distance to the final point of multi-leg route. Measured along the route.
ETED – estimated time enroute to destination.
ETAD- estimated time of arrival at destination.

ROT – rate of turn.
RDA – rudder angle
SDA – set and drift angle. Used in combined set & drift instrument.
SDD – set and drift direction. Used in combined set & drift instrument.

Any of the direction acronyms above may have a suffix of ‘M’ to denote that they are in degrees magnetic. Without this suffix, assume degrees true. I.e. HDGM vs. HDG.

GPS for PolarView & PolarCOM

The question of which GPS to use with PolarView and PolarCOM comes up almost every day. There is certainly a great variety of GPS devices out there, with many pros and cons to each.

That said, based on user feedback, GlobalSat BU-353 GPS “usb puck” seems to be a definitive leader, for many years consistently getting high marks for reliability, precision and generally doing what these devices are supposed to be doing. This GPS supports Windows (XP, Vista, 7), Mac OS and Linux.

Drivers for Windows and Mac are usually supplied with device. You can also download drivers online by following this link. These drivers are from original chipset manufacturer and seem to work best. They are listed for “PL-2303″, which is a type of microchip used in GlobalSat GPS device. Linux already includes drivers in most popular kernel distributions.

The only issue BU-353 tends to suffer from is “wandering” speed/course
when at complete rest. This is easily remedied by using data dampening option in PolarCOM, under “Configuration->Data->Data Dampening”.

A going price for GlobalSat BU-353 seems to be around $35 at Amazon or elsewhere, so they are easy on the budget too. Follow this link to order one.

PolarCOM “True” Wind Calculation

When used with “relative” (apparent) wind data source, PolarCOM provides two modes of “true” wind calculation. These modes are labeled “STW” (Speed Through Water) and SOG in the configuration. STW is a “traditional” method, used by most hardware wind instruments. It needs no GPS input and requires STW and HDG (your vessel heading) to calculate “true” wind. It also results in an approximation of “true” wind.

SOG mode provdes more precise “true” wind calculation, but it also requres COG as well as HDG. That means you still need a heading sensor to calculate “true” wind – having only GPS input without heading is not sufficient.

If you are interested in explanation as to why that is, read on:

Let’s say you have the following -
1. Relative apparent wind (from VWR/MWV NMEA sentence) as delivered by windvane
2. GPS information including COG/SOG.
3. nothing else

Consider this – your vessel is heading in some direction which is most likely NOT aligned with COG. Relative wind is a vector that you can calculate based on a coordinate system that has boat heading as one axis (and another axis perpendicular to it).

On the other hand your SOG (and SOG induced “wind”) is a vector that by itself can only be considered in a system with one axis along the COG (and another perpendicular).

Without heading there is nothing to reconcile these two systems and no way to do any reasonable operations on these vectors. You need heading to convert one of these vectors to the coordinate system of the other.

Here is a practical example using PolarCOM. The first set of dials (img 1) shows COG and heading that differ by 20 degrees. The true wind is calculated here based on SOG (and using both COG and HDG to adjust vectors). You can see true wind both relative to the boat (second dial from the left) and as an absolute direction (last dial on right). There is no STW (as the heading dial shows).

Img 1

On the second image (img 2) I adjusted heading to match COG. This is what would effectively happen if you used SOG for true wind calculation but did not have an adjustment angle (and assumed direction of travel matching heading).

It is quite clear that true wind resulting from such calculation is not the same as the one that results from properly accounting for COG/HDG difference. And the difference is not insignificant – 30 degrees and about 40% stronger.

Img 2

Incidentally, third picture (img 3) shows calculations using STW and heading. I set STW to be equal to SOG, which is not necessarily true, but it helps make an example simpler. As you can see it is also incorrect, but the result is essentially the same as when using SOG alone without proper heading. I.e. there is no gain in calculation precision.

Img 3

PolarCOM Alpha 0.1

– Initial Alpha release
– Support for multiple NMEA sources and bridging (serial, TCP/UDP server, file)
– Digital instruments for speed/course/position/depth/satellite status
– Day/night color schemes