Another GPS option for PolarView & PolarCOM

May 5, 2011

Just recently I got a chance to order and use another compact USB GPS receiver – ND 100 by GlobalSat.

This receiver uses the same drivers as it’s cousin – the ever popular BU-353 about which I previously blogged here.

Since I already have the Prolific chipset drivers installed, ND-100 worked right out of the box. In my test it quickly acquired a fix and provided position to within about 5 feet – all *indoors*. It also appears to have a bit less of a stationary “course drift” than my BU-353s, though that could be individual device issue.

The primary advantage of this device is a form factor – rather than being a GPS “mouse” it is a “USB stick”, the size of average external flash drive, though it feels a bit heftier. It fits well into my netbook and avoids messing with wires. That said, one drawback may be that it requires additional space to the side of netbook, least it catches onto something and pops out of the USB socket. No big deal though, it can be plugged right back in – and no harm done. PolarCOM will reacquire the connection shortly.

All in all another good option, available on Amazon for about $35.

Navigation / Instrument Acronyms

February 22, 2011

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

February 17, 2011

GlobalSat BU-353

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.

Fun with ENC charts

August 29, 2010

Looks like NOAA may be using automated conversion software to create ENC charts from satellite images. It works great most of the time, but sometimes things don’t go as planned. In this chart (US5NY43) Mid Hudson Suspension Bridge seems to be charted based on a shade of the bridge rather than bridge itself, moving it somewhat North. Stated accuracy of 1:40000 scale chart is about 140′ so this one is probably just about within the limit.

Good navigators always remember that chart is not a substitute for a proper lookout.

P.S. A bit more on this – the following is my guess, correct me if I am wrong.

So, NOAA may be trying to do the right thing. Note that the satellite image is taken from position slightly due North of the bridge, rather than vertically. From that point of view bridge as tall as this one (134 ft) would be visually shifted South relative to anything at “sea”/water level. On the other hand, if the sun was at high noon and directly overhead, shade from the bridge would be precisely under it at exactly the sea level, and would provide a perfect outline of the bridge on a chart. I think this method works “most of the time”, in particular for images taken during summer months in Southerly latitudes.

Here we have a relatively high Northern latitude, and photo likely not taken at noon, so the sun is low in the southern sky. Because of that, the shade is located North of the bridge. The “real” bridge position should probably be charted in the middle between the shade and the bridge on the satellite photo.

Quick Video Demo

June 2, 2010

Below are a few videos demonstrating some of the basic functionality of PolarView. I did not spend much time on it so quality is not great. I still need to figure out how to annotate mouse clicks and keystrokes.

Some of the features in the video are not yet available in the current release – but will be in the upcoming version.

Demonstrating how to lay a route:

Miscellaneous options including:
– Setting and moving a waypoint
– Changing palette colors
– Showing tide information for a given tide station
– Searching chart list for a specific chart

Using a GRIB viewer:

A better demonstration of a GRIB viewer (using an older version of PolarView), made by a user. Thank you!

PolarView/PolarCOM Update

November 23, 2009

This is an intermediate maintenance release that fixes a few issues in version 1.0 of the product.

PolarView: show bearing/distance information when moving waypoint used in route.

PolarCOM: solves a number of serial port connectivity issues – if you had a problem making your GPS work with PolarCOM, this update should resolve it (or so I hope).

New Product – “Real Soon Now”

October 22, 2009

I generally avoid talking about things that are not quite finished. However – people have been asking about “live GPS” navigation product for a while. Until now the reply was – “it is being worked on”.

So now, to show that it is not entirely the “vaporware” it may appear to be, here is a screen shot of what the standard navigation view looks like. It shows a ship on a chart (in “North up” orientation), “radar rings”, and a simple set of dials including POS, SOG, COG and analog apparent wind.

1000 software simians are currently banging on 1000 keyboards to thoroughly test this software, and document every aspect of it, before it becomes publicly available.

New Polar Navy navigation product.

New Polar Navy navigation product.

Let me know what you think!