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

2017-11-29 Thread Oleksiy Muzalyev 

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=-90.19947052001955=14=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.



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

2017-11-29 Thread Martin Koppenhoefer 


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

2017-11-27 Thread 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=-90.19363403320312=14=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=UTF8=1511844559=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 <oleksiy.muzal...@bluewin.ch>
Sent: Nov 27, 2017 11:05 PM
To: Talk Openstreetmap <talk@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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Re: [OSM-talk] GPS Altitude vs Pressure Altitude article, Tool for measuring elevation above sea level

2017-11-27 Thread Jack Armstrong dan...@sprynet.com 
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.muzal...@bluewin.ch>
>Sent: Nov 27, 2017 11:05 PM
>To: Talk Openstreetmap <talk@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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[OSM-talk] GPS Altitude vs Pressure Altitude article, Tool for measuring elevation above sea level

2017-11-27 Thread Oleksiy Muzalyev 

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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