Garmin Interview about GPS and Rowing

Jessica Myers, Senior Media Relations Specialist at Garmin was kind enough to respond to my request for an interview about their GPS units and their suitability for rowing. She also passed on a couple of photos - one of their facility in Olathe, KS and the other of the Garmin Forerunner 305 - one of the units she recommends for rowers.

The interview doesn't provide any of the technical details that I might have liked to see. I had hoped that the first question might have led to something more for our readers. I did ask for more, but this was all the information that was available. In fact the responses really don't respond to any of the criticism about using GPS in rowing. On the other hand she does provide a few interesting bits - such as the availabliity of a floating unit, and the availability of an (I'm sure pricey) 5 Hz units.


[RS]: One of the criticisms form rowers is the frequency of measurements. My unit returns measures every second (1 Hz) - are there units available now, or coming soon, that sample more frequently?

[Garmin]: With a WAAS enabled unit (which most GPS devices now have), the GPS update rate is once per second. The exception to this is with some aviation units where the GPS update rate is faster (5hz update = 5 times/sec). With the one/second update rate, GPS does a great job of calculating an overall speed, but it does not always provide as thorough information in relation to acceleration and deceleration.

[RS]: How is velocity calculated exactly? Is it based on previous postions? In other words, does it truely reflect the velocity at that moment in time - if not, how far back in time is the measure going (we are interested in even tenths of seconds here).

[Garmin]: I can't provide you with specifics on the algorithms we use to calculate the velocity because it's proprietary.

[RS]: Another concern (though some would say benefit) is that on-water measures are relative to land - so that a boat sitting still, but in a current, would register a velocity. Is there a way to calibrate the unit - in effect to define what is zero velocity to take currents out of the equation?

[Garmin]: No, we don't currently have a way to calibrate the unit so that it takes current out of the equation.

[RS]: The extra maps for the units are (relative to the cost of the unit itself) a bit pricey - I realize they give a great deal of information but some coaches are really only interested in a small body of water less than 10 km in any direction - would there ever be an option to obtain a more detailed map, but of a limited area?

[Garmin]: I can pass on your request about having cartography cards with smaller segments of information. One of the reasons the cards are divided as they are is because the primary audience that purchases this mapping data is fishermen. As you might expect, they often prefer to have more information so that they're not limited to one area while on water.

[RS]: Are there any materials on your web site that you would recommend people look at?

[Garmin]: Regarding info on our website -- it depends on what type of info you want. If you're looking for basic GPS info there are several places: and If you want more information about WAAS (which is what I referred to above that makes GPS more accurate):

[RS]: Are there any of your units in particular that you would recommend for us to use?

[Garmin]: We offer several different GPS units that your readers might like. If they want a unit that is more devoted to fitness, I recommend the Forerunner 305: I've personally never tried this unit rowing, but I know of others who have and they like it. Note, the Forerunner 305 doesn't show maps, so if maps is important you don't want this unit. If you do want maps, the top of the line unit is the 76CSx. One of the nice things about this unit is that it floats. It also has our new, highly sensitive GPS receiver (SiRFstarIII receiver) that lets it acquire a signal faster: If you want a unit with a faster GPS update rate, the GPSMAP 496 has a 5hz update rate. The 496 is an aviation unit, and therefore has lots of other features that you're probably not going to want or need. It's also costs a little more because of the aviation components that are on the unit. Another popular unit on the water is the Foretrex: Windsurfers especially like this unit because it lets them keep their hands free while still monitoring their speed and tracking their waypoints. As with the Forerunner, this unit doesn't do mapping, but you can take all of the waypoints acquired on the unit and download them to where you can see your tracks on a variety of maps including Google Earth. has a free and subscription portion, so you can always check it out for free if interested. It has a very big following and is very popular with those doing water sports.

[RS]: Many thanks for your time.

[Garmin]: I hope this information is somewhat helpful. Please let me know if you have any additional questions.

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