Problems with Altimeter

This is my trip on last week.

Temperature outdoor 22 °C on the top is snow 2 °C.

Do you use DEM?

stupid question: how do I use DEM?

do I just calibrate with DEM and it downloads the DEM data for my current region onto the watch?

What's the point of the altimeter when using DEM? DEM just means mapping 2D GPS coordinates to a height map, so no altimeter right?

Edit: I just calibrated using DEM, at least it confirmed my known altitude 601m. But it was very quick, I don't think it downloaded anything else onto the watch. 

I am not using DEM. Only old Instinct one year ago.

I forgot to take off my watch in the sauna and the altimeter showed just as well. So I think if you change your watch, you will be satisfied. I really like the fact that I have a 50% battery on my watch in the morning and after a few hours in the sun I have a 53% battery in the evening. :-) Stamina is excellent! Today I'm going on a trip again. Lots of hilly terrain and alternating temperatures, so we'll see.

henzim said:

I can only imagine the calibration of a sensor (such as barometer) to a different measurement value (pressure) would result in an offset being added to the actual reading. And should not be needed unless the hardware is faulty and has a different offset

You are correct that the barometer will adjust to the correct pressure unless faulty. The reason you have the ability to calibrate pressure is because of sudden changes that will change the readings and allowing the barometer to correct itself takes time and it's not immediate.  Here's an example.  If the weather is nice, I'll roll down my window while driving.  If I'm on the highway at high speeds the wind force will change the barometer drastically and give me crazy elevation changes.  When I stop the barometer will correct itself, but this will happen gradually and may still be off by the time I start an activity. Anyway, looking at your watch pictures it's my belief you have a faulty temperature sensor.  You've eliminated the possibility of moisture being the cause, but I'm puzzled as to why you have the same results if the watch is worn or not. When wearing your watch your body temperature won't increase that high during an activity to cause much of a temperature change as you had when not worn and then put back on, yet the results are the same.  Strange. 

I'm still trying to figure out henzim's issue and maybe someone else with an Instinct Solar can assist as I don't own one myself.  The temperature widget displays the internal temperature of the watch when not connected to a Tempe sensor and is used for barometer readings and isn't designed for ambient temperature.  If the watch is removed and set out of direct sunlight or a while, or if it's submerged underwater while swimming, it will display fairly accurate ambient temperatures.  It's 72 degrees F in my house right now.  I'm wearing a 945 that's been on my wrist for a week straight.  I have a 935 sitting on my desk.  Both watches are displaying 68F/20C.  I asked henzim to remove his watch and conduct an indoor workout to eliminate the possibility of an obstructed barometer port by either skin or sweat to see if that was the cause of his issues.  He did just that and displayed photos showing the watch temperature of 71F/22C.  What I noticed was prior to removing his watch, the graph was fairly stable and showing 93F/34C.  Is this normal for the Instinct Solar?  Maybe the temperature sensor in the Instinct Solar is located in a different spot where it's more sensitive to body temperature then the Forerunner's?  It seems quite high to me and I'm suspecting a defective temperature sensor.

The solar has a sensor near the bottom of the watch. So it's affected by body temperature. Instinct shows an exercise temperature of 26 to 29 ° C during exercise.

Thank you so much for your effort!

That is a very interesting question and obervation, looking at my watch now, it shows 32°C. Interestingly, the maximum over the last 4 hours was 38°C (100.4°F).

The lowest apparently was 27C.

That does seem awfully high. Outside we had like 15C today and I don't have a fever. 

Last 4 Hours - 25 min and 31 max. I am at home last 4 Hours.

I understand that any heat or cooling source will affect the temperature sensor in the watch.  My question is to what degree?  As I said, my 945 and 935 are currently displaying 68F.  The 945 is worn, and not being affected by my body heat.  When henzim had his Instinct Solar off he had a similar temperature of 71F as both my watches, but when worn it was displaying 93F.  This is what I find as puzzling.  I don't have any issues with my barometric altimeter.  Why aren't I seeing a much higher temperature on my devices when worn like you and henzim are seeing?  I'm now question that the temperature sensor is more insulated against body temperature in the Forerunner's than the Instinct Solar.  This larger temperature difference would affect the barometer reading, (From the Garmin Support website: Since barometric altimeters are not temperature-compensated, changes in ambient air temperature can affect altimeter accuracy.)  This would explain why this isn't a problem the the Forerunner's but a major topic with the Instinct line.  Even with exercise you're not expelling that much heat.  Please keep in mind that this heat increase is without heat dissipating: 

"For example, exercise performed at 80 to 90% of maximal aerobic capacity (VO2 max) could increase core temperature by 1°C every 5 to 8 minutes if heat was not dissipated."