[OSM-talk] GPS Altitude vs Pressure Altitude article, Tool for measuring elevation above sea level

[Oleksiy Muzalyev]

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 Dancer at 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 <oleksiy.muzalyev at bluewin.ch>
>> Sent: Nov 27, 2017 11:05 PM
>> To: Talk Openstreetmap <talk at openstreetmap.org>
>> 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
>>
>>
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