Re: [OSM-talk] GPS Altitude vs Pressure Altitude article, Tool for measuring elevation above sea level
On 29.11.17 23:39, Martin Koppenhoefer wrote: sent from a phone On 28. Nov 2017, at 06:10, Oleksiy Muzalyev wrote: Besides the number of the satellites increased lately, and the quality of the GPS receivers is also improving. And everyone who has got a modern smartphone has got a GPS altimeter. Some smartphones and some consumer gps units also feature barometric altimeters. Our consumer GPS units, especially those in smartphones with their suboptimal antennas, are unsuitable for measuring elevation precisely, the accuracy in the z-direction, from what emerged from previous discussions about this, is about 10 times inferior with respect to x/y. cheers, Martin It seems the global sources of elevation are not precise either. For example, the OSM shows correctly that the elevation in this part of the New Orleans is below sea level: http://ausleuchtung.ch/elevation/?lat=30.017679032856247&lon=-90.19947052001955&zm=14&rd=2 However, the Google Map Elevation API shows 0 meters for the same area: http://www.enetplanet.com/ . It means the elevation data which was entered by the local mappers is more correct. And this is essential information for such flood risk zones. Certainly, one should calibrate an altimeter. For example, measuring the elevation at a location with the known elevation. I think it would be even better to have both the GPS and the barometric altimeter, and both calibrated on the day of actual measurements. Best regards, O. ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] GPS Altitude vs Pressure Altitude article, Tool for measuring elevation above sea level
sent from a phone > On 28. Nov 2017, at 06:10, Oleksiy Muzalyev > wrote: > > Besides the number of the satellites increased lately, and the quality of the > GPS receivers is also improving. And everyone who has got a modern smartphone > has got a GPS altimeter. Some smartphones and some consumer gps units also feature barometric altimeters. Our consumer GPS units, especially those in smartphones with their suboptimal antennas, are unsuitable for measuring elevation precisely, the accuracy in the z-direction, from what emerged from previous discussions about this, is about 10 times inferior with respect to x/y. cheers, Martin ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] GPS Altitude vs Pressure Altitude article, Tool for measuring elevation above sea level
Thank you! In this article it is claimed that the barometric altimeters are more accurate than GPS altimeters: https://www.satmap.com/knowledge/Active_12/What_is_a_barometric_altimeter_.html if re-calibrated periodically. The barometric altimeters are available [1] , and they are not expensive. However, a GPS altimeter also can be kind of calibrated by measuring an elevation at a point with the known altitude right before starting to perform the actual measurements. Besides the number of the satellites increased lately, and the quality of the GPS receivers is also improving. And everyone who has got a modern smartphone has got a GPS altimeter. With this application if one clicks say at New Orleans, Louisiana, at this point http://ausleuchtung.ch/elevation/?lat=30.00890908440004&lon=-90.19363403320312&zm=14&rd=2 it is immediately clear that this area of the city is below sea level. But this information is not visible clearly on the OSM map otherwise, even one the Cycle layer. [1] https://www.amazon.com/Multifunction-Outdoor-Thermometer-Sport-YingYing/dp/B01KH4XK8W/ref=lp_219368011_1_11?s=sports-and-fitness&ie=UTF8&qid=1511844559&sr=1-11 Best regards, Oleksiy On 28.11.17 04:25, Jack Armstrong dan...@sprynet.com wrote: Congratulations on your accomplishment. Of course, elevation above sea level (MSL) for a fixed point on the ground does not change no matter the pressure altitude (barometer setting). Pressure altitude vs. using a QNH of 1013 for flight levels (high altitude), is something mostly only pilots and air traffic controllers are concerned with and have no bearing on ground mapping. The QNH or altimeter setting simply help the pilot and/or controller better understand an aircraft's height above the ground. But, I assume you understand this. -chachafish (38 years as an air traffic controller) -Original Message- From: Oleksiy Muzalyev Sent: Nov 27, 2017 11:05 PM To: Talk Openstreetmap Subject: [OSM-talk] GPS Altitude vs Pressure Altitude article, Tool for measuring elevation above sea level Hello everyone, After reading a good article "GPS Altitude vs Pressure Altitude" [1] I wrote a simple tool to calculate an elevation above the sea level at the point of a click on the OSM map: http://ausleuchtung.ch/elevation/ More details are at the Diary entry: https://www.openstreetmap.org/user/Alex-7/diary/42830 [1] http://www.borgeltinstruments.com/GPSvsPressurealtitude.pdf Best regards, Oleksiy ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
Re: [OSM-talk] GPS Altitude vs Pressure Altitude article, Tool for measuring elevation above sea level
Congratulations on your accomplishment. Of course, elevation above sea level (MSL) for a fixed point on the ground does not change no matter the pressure altitude (barometer setting). Pressure altitude vs. using a QNH of 1013 for flight levels (high altitude), is something mostly only pilots and air traffic controllers are concerned with and have no bearing on ground mapping. The QNH or altimeter setting simply help the pilot and/or controller better understand an aircraft's height above the ground. But, I assume you understand this. -chachafish (38 years as an air traffic controller) -Original Message- >From: Oleksiy Muzalyev >Sent: Nov 27, 2017 11:05 PM >To: Talk Openstreetmap >Subject: [OSM-talk] GPS Altitude vs Pressure Altitude article, Tool for >measuring elevation above sea level > >Hello everyone, > >After reading a good article "GPS Altitude vs Pressure Altitude" [1] I >wrote a simple tool to calculate an elevation above the sea level at the >point of a click on the OSM map: http://ausleuchtung.ch/elevation/ > >More details are at the Diary entry: >https://www.openstreetmap.org/user/Alex-7/diary/42830 > >[1] http://www.borgeltinstruments.com/GPSvsPressurealtitude.pdf > >Best regards, > >Oleksiy > > >___ >talk mailing list >talk@openstreetmap.org >https://lists.openstreetmap.org/listinfo/talk ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk
[OSM-talk] GPS Altitude vs Pressure Altitude article, Tool for measuring elevation above sea level
Hello everyone, After reading a good article "GPS Altitude vs Pressure Altitude" [1] I wrote a simple tool to calculate an elevation above the sea level at the point of a click on the OSM map: http://ausleuchtung.ch/elevation/ More details are at the Diary entry: https://www.openstreetmap.org/user/Alex-7/diary/42830 [1] http://www.borgeltinstruments.com/GPSvsPressurealtitude.pdf Best regards, Oleksiy ___ talk mailing list talk@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk