Hi, Thanks for the precision. So they are basically prone to the same problem (which is reassuring). My guess is that the true befits is that they add a compass with the barometer so you can take a heading reading when not moving... I guess that is worth 100 bucks!
Guess we’re moving away for the topic here... shitty ADHD! :) Nicolas Cadieux https://gitlab.com/njacadieux > Le 21 avr. 2021 à 08:26, kirk <[email protected]> a écrit : > > > Hi Nicolas. > > You can set the barometer my using a known point and elevation or by setting > the current atmospheric pressure. As with an anologue altimeter, your > readings will change throughout the day as the pressure changes. This is less > of a problem if you are out on a sunny day with a high pressure cell with a > small pressure gradient. but becomes bit more problematic if a low pressure > system is moving in. > > > Sent from my Galaxy > > > -------- Original message -------- > From: Nicolas Cadieux <[email protected]> > Date: 2021-04-21 9:14 a.m. (GMT-04:00) > To: David Strip <[email protected]> > Cc: Qgis Users List <[email protected]> > Subject: Re: [Qgis-user] (no subject) (elevation question) > > Hi, > > Interesting but I very much doubt they are not applying a geoid on top of > the ellipsoid. If they can put maps of the earth on the device, they can put > a geoid with a posting of 15´x15´! > > I have been wondering about those barometric altimeters GPS for back > packing. I have a none electronic altimeter with me normally but it only > really good if you consider the temperature changes. > > Nicolas Cadieux > https://gitlab.com/njacadieux > >>> Le 20 avr. 2021 à 23:03, David Strip <[email protected]> a écrit : >>> >> >> In the course of trying to find what geoid model Garmin uses, I found this >> on a Garmin support page: >> . It is not uncommon for satellite heights to be off from map elevations by >> +/- 400 ft. Use these values with caution when navigating. >> Apparently some, but not all, models of the Garmin64 have a barometric >> altimeter. Depending on your actual model, this may or may not apply. >> >> >>> On 4/20/2021 8:23 PM, Nicolas Cadieux wrote: >>> Hi, >>> >>> David gave you a very good answer. Your looking at a 11 meter difference. >>> That is not much. The first thing would be to look at the gps measurement. >>> (Any trees? Good satellite constellation? Any obstacles?). At best, your >>> looking at a 6 to 10 meter error vertically. SRTMs are affected by trees. >>> That would make the SRTM higher (not your case). Last thing to look at the >>> the differences between the gps geiod model (a model of the average sea >>> level). SRTM use EGM96. Your GPS probably uses something a bit more >>> modern. You can easily get a 5 meter error between two Geiods. >>
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