roybassist

It will work with a 4GB microSD. I only have about 1.4GB loaded on a SanDisk 4GB HDSC, so I am not sure if it will recognize the rest of the memory. If no one can positively answer this one, I will try going over 2GB tonight when I return from work, and post a response, but it wouldn't surprise me if someone has already tried it. Would you clarify which gpsr you are using and that it is using a Sandisk 4gb Micro SDHC card? It was my understanding the SDHC format was not compatable with any of Garmin's handhelds. Cards up to 6 GB have been used in the 60 and 76 series units. They are recognized and work with the exception that if you load over 2 GB of maps, the unit won’t see any of them. That’s probably why some people think they don’t work. The free space on any size card can be used for track log storage and it is accessible in mass storage mode and may be used for other purposes. Edit: forgot to mention that there is also a limit of 2025 map segments on these units.

Did you manually calibrate the altimeter to anything (gps elevation or contour for example) at the start? Auto calibration will eventually correct errors, but if you don't calibrate the altimeter on startup, the initial barometric elevation can be way off due to pressure changes since the last time you had the unit on. It could take quite a while for auto calibrate to correct it. Should have been pretty good within about an hour though. If the GPS elevation seemed to be correct, it was probably just a lucky coincidence. Rigorous comparisons have shown that a barometric sensor with auto calibrate on is more accurate than GPS elevation. GPS elevation varies a lot with time. Here is a typical example of a test plot: http://www.gpsinformation.net/waas/g76s/g76s-baro.html I have seen better test data on the web, but I can't find any of it at the moment.

Yes, but it can display only the barometric elevation as a continuously updating data field. Only if you specifically manually calibrate to GPS elevation. If you don't, it will start with the current barometric elevation, which will be affected by any pressure changes since you last had the unit turned on. If you want it to start with anything else, you have to calibrate it manually using one of the choices I listed in my previous post. You can calibrate manually by going to the altimeter page, pressing menu and selecting "Calibrate Altimeter". There are a couple of other ways to access the calibration screen, but they all take you to the same place. Only if you have autocalibration turned on. Yes. MENU>MENU>Setup>Altimeter. No. Elevation displayed as a continuously updating data field will always be based on the barometric sensor. There is no other option. If you turn off autocalibration, the barometric sensor just won't be automatically corrected for changes in weather. If the sensor is initally calibrated to a known elevation, turning autocalibration off will usually be more accurate in the short term and less accurate in the long term. The only way you can display GPS elevation on this receiver is to go to the Satellite page, press MENU and select "GPS Elevation". This gives you a snapshot of the GPS elevation at that moment. To get it to update, you must back out and do it again. Many have asked Garmin for years to offer GPS elevation as a data field choice, but Garmin has been unresponsive on this. This would be nice when traveling in a pressurized aircraft, but I can't think of any other reason to use it. When calibrated using the best data you have, even if it's GPS elevation, the barometric elevation will normally be more accurate than GPS elevation alone. Of course, you have to use some common sense. The barometric altimeter works well in the gradually changing environment normally encountered in nature. If you open a car window on the highway, or make a big change in the setting of the ventilation fan while the windows are closed, you will see the elevation reading affected. But if you maintain those conditions long enough, autocalibration will do a reasonable job of adjusting for them.

Yup. Yes and no. You can: 1) Calibrate to the elevation where you are, if you know it, 2) Calibrate to the barometric pressure where you are, if you know it (this is the sea-level adjusted barometric pressure reported by weather stations everywhere; no fancy calculations required. A weather station within 25 miles is plenty close for this purpose) 3) Calibrate to the current GPS elevation. In this case you are at least as well off as those who don't have barometric sensors, since GPS elevation is all that their receiver can give them. Unfortunately, GPS elevation is subject to relatively large errors, and it changes constantly as satellite geometry changes; but it is pretty good as a starting point for autocalibration (see below) if you don't know your current elevation or barometric pressure, or 4) Calibrate to nothing, and eventually (30 minutes to an hour in typical situations) autocalibration (if you have it turned on) will still get you pretty close to a "real" elevation. That isn't a problem if you turn on autocalibration. Autocalibration compares the difference between the elevation determined by the barometric sensor with a somewhat long-term average of GPS elevation, and calibrates the barometric elevation to minimize the difference. Over a period of time (don't as me how long), the average GPS elevation is relatively accurate. By calibrating the barometric sensor to the average GPS elevation, the effects of pressure changes are compensated for. Automagically. It's very sophisticated, and it works very well. Mine corrected a deliberate miscalibration of 100 feet in about an hour. That's much faster than barometric pressure normally changes. Amazingly, autocalibration seems to work well over the length of a day even when I turn my receiver on only occasionally to get a position fix and then turn it off again to save batteries. A fellow named Chris Malcolm once documented that the algorithm seems to have what he called a "fast catch-up mode" to handle this situation. Unfortunately, Mr. Malcolm's excellent web page on autocalibration is no longer where it once was, and I've been unable to find it elsewhere. Of course, even the average of GPS elevation isn't perfect, so your receiver may still be off some, but it's pretty good, and definitely better than GPS elevation alone. The downside is that for periods of time that are short enough for the barometric pressure to be constant, autocalibration may actually reduce accuracy, as hogrod stated very well previously in response to the OP:

A guy by the name of Colin Wilson who lives in the UK purchased a unit while on holiday ("vacation" to us Americans) in Canada. When he got home, he found Garmin Europe wouldn't sell him the maps for it without a hardware purchase. Ticked him off badly enough that he created this web site ( http://coreutilities.netsynk.co.uk/garmin/ ), where you can get his story firsthand. I don't know whether Garmin's policies have changed since his experience; nor do I know whether this policy applies to all units. I take no position on the issues involved or Colin's complaint. I provide the link only because you asked for information on any issues that might arise out of buying the unit in the U.S. You may want to investigate this for yourself before making a decision.

Many thanks to those who have responded. The comments and photos you provided were just what I was needing! Very helpful. I really appreciate it! I think others will find it useful also.

I've seen posts from a few people saying that they thought the screen of the Colorado wasn't as bright as the screen on the 60C/76C series, some of them saying they think they might have to run the backlight more on the Colorado. What doesn't quite add up for me, though, is that if it were that bad, it seems like there would have been a lot more comments about it by now. I'm considering whether to buy a Colorado, and this is a potential make-or-break issue for me. I currently own a 76CS. I know the screen on the Colorado is bigger and higher res than the one used in the 60/76 series; but if the brightness of the Colorado screen isn't at least comparable to the 60/76 screens, I don't think I want one. I am mostly concerned with outdoor daylight conditions, where I've never needed the backlight on my 76CS. If the Colorado screen is ok under those conditions, I think I would be satisfied with it. Since my interest is in its outdoor performance, going to a store and looking at it indoors probably wouldn't be much help. I would really appreciate hearing from more people who have both the Colorado and a 60/76 series unit regarding the comparative brightness of the screens. Any other comments regarding the usability screen would be welcome. Side-by-side comparison photos with a description of the ambient lighting conditions would probably be really helpful. Many thanks!