Although SIRIF, the industry leading GPS sensitivity chip, was introduced about three or four years ago, Garmin, in the last 120 days, may have finally been forced to include it in what they are calling their "High-sensitivity receiver" eTrex series GPS. If it is SIRIF then you can expect acquisition that is 30 times faster than current units and (finally) a strong signal under trees, inside most structures, and in natural and city canyons.
If you are considering a new GPS you may want to wait a few more weeks to see if the new chip is in fact SIRIF.

I am not up on what is going on in the industry so I don't know if Garmin was forced to do anything or not, but the Sirif chips have been in place in their 60CS series for the last several months at least, so you can get them now.

The 60 series is more expensive then the trex series.

For what it's worth, I notice a clear advantage in terms of speed of acquisition, accuracy, and signal strength in cover in my 60csx as compared to my old etrex.

You can get the "High-sensitivity" eTrex now as well. The problem is Garmin will not disclose, at least so far, which chip they are using in the "new" eTrex. I have used the SIRF chip for years in my other GPS units; and you are right, there is really no comparison. I need another handheld backup unit but I will not buy anything except SIRF; so I will wait and see.

^ Which "other GPS units" have you been using with SIRF? Just curious.

I have had a 60CS series since they first came out. Not SIRF, but its performance is already incredible compared to my previous generation GPS. So the improvement will have to be quite something to get me to upgrade *just for that*.

I think I'll wait until Garmin includes support for the Galileo system. Some other manufacturers are already. Garmin has been a bit slow in many areas lately, too slow to rebuy a model just for one improvement that already should have been in their models a few years ago, like SD cards.

Did your old etrex have WAAS enabled or was it capable of WAAS augmentation? Some of the earlier firmware on the earlier etrex's weren't WAAS capable.

It is actually very difficult to measure GPS accuracy, you would really need to connect the GPS to a PC via the serial or USB port and collect the output data i.e the GPS RTCM output messages then have some software measure statistically the Spherical Error Probability SEP (3D) or the Circular Error Probability CEP (2D) over a period of say 24 hrs. As the GPS satellite constellation is constantly moving or arcing across the sky. The geometry of the GPS constellation gives rise to something called Geometric Dilution of Precision GDOP. GDOP will have an effect on the accuracy of the GPS fix computation throughout the day. Good quality GPS receivers will have a CEP of around 20-25 metres without using differential means.

SEP and CEP is a function mainly of the accuracy of or lack of jitter in the Receivers clock Quartz TXCO and the sensitivity of the GPS antenna design (i.e. many survey antennas are designed to specifically reduce Multipath) and having the best low noise high gain front end amplifier for the L1 frequency (1575.42Mhz). Most of the worlds GPSs TXCO Quartz clocks are manufactured by a single company in New Zealand. Higher quality GPS receivers generally have a separate RF ASIC chip (front end RF PLL filter and RF low noise amplifier) for the front end rather than being integrated on to the same Digital Signal Processor Chip and microcontroller.

For the best improvement in accuracy, differential GPS needs to be employed. This can be achieved by turning on WAAS on the GPS or use something like an external 2 channel MBX-3 Automatic differential beacon receiver which picks up a radio broadcast signal from a differential GPS radio beacon. CEP with WAAS enabled should be around 3-5 metres with a good quality GPS receiver. CEPs of less than 2 metres are possible with a differential beacon reciever with the beacon being less than 100Km away. To improve PRN lock in a poor sky view environment i.e. foliage, being in a canyon or in a high rise area of a city, with a hand held commercial GPS then a secondary high gain, low multipath external antenna should be employed as different GPS chipsets i.e. SIRF or Trimble Lassen etc used internally will have very little noticeable effect unless an L1 L2 RTK GPS receiver is being employed (very expensive survey kit)

The SIRF chipset designs are excellent low cost, low power, efficient designs but the GPS chipset has very little to do with accuracy, speed of acquisition or signal strength as other factors inherent in the GPS system together with the other design choices in the overall GPS receiver design as a whole are much more influential in achieving accuracy and speed in a wide variety of environments. i.e. even the choice of battery in the GPS design will have a more of an impact in the overall GPS performance.



A full 12 channel GPS receiver, maybe Doug could have someone design the GR-10 GPS to fit into the Photon Freedom Micro light.

Anyone doing that is simply wasting their time and your money. A functional Galileo system is at least 8-10 years away away, even assuming they sort out the political and financial deadlock they find themselves in currently. Galileo was a political statement from day one and it has turned out to be an economic non-starter like many predicted. While it would be nice to have an alternative system, don't hold your breath. JMHO opinion, of course.

This Aug 2005 News Release reads to me like Garmin is commited to SIRF.

I think you're right. I hadn't kept up on the SNAFU that is currently going on, thought it was still on-track for being up in the next few years.

I am VERY happy with my current Garmin 60CS (no SIRF). It is so incredibly faster and works in so many more tough situations than the previous gen I had. I typically get fabulous results, can show me which side of a single track dirt road I'm walking on, stuff like that. I have no quibbles with the way GPS is allowed to work right now. I guess what troubles certain people is the U.S. military can degrade it or turn it off at their whim.

So what is the SiRF actually doing? I get the impression it uses less power (which is good), and gets its superior sensitivity mostly "mathematically", practically it may not offer much improvement compared to the same unit that was already very sensitive. Of course, everything about how GPS works involves brain-burning math...

cfraser:

I buy most of my GPS hardware and software from SEMSONS.COM. However lots & lots of folks carry SIRF receivers.

FWIW, I asked a couple of heavy-duty outdoor Garmin GPSMAP 60CS users who upgraded to the 60CSx. They said you definitely CAN notice the faster sat acquisition speed with the SiRF-equipped 60CSx. Under all conditions. So, it's not just some manufacturer hype, it's a worthwhile feature to look for in a new purchase.

As for greater ability under covered conditions, that was a little less definite, but they "thought" it seemed better. Neither are deep canyon or rainforest etc. hikers...