GPS altitude correction

pajaku shared this idea 9 years ago
Completed

It`s not perfect but when most of phones aren`t equipped with pressure sensor this correction minimalise error.

Replies (32)

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don`t understand this question. GPS data are computed from NMEA data. So how should I improve altitude by same data from where was altitude computed??

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Im not GPS freak. But exmaple:


GPS alt: 150 m / Real 110 / corrected 115


In OruxMaps and in some apps for GPS managing under Winows CE/ Mobile (years ago) is option Altitude correction NMEA which use geoid for that. I remember old days with Acer n300 and BT GPS, this correction was very helpful.

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Another thing is off line altitude like in Garmin GPS. Hier I can use open source DEM map wich is give information for other maps. So I can see alt under cursor or I can use alt date for profile. Or I can use topo map with DEM info and other maps are use them too even this map isn`t active.


So: off line DEM data maybe would be nice too for track calculated inside locus or even for those computed in the cloud off line DEM date stored on SD card could be used insted of fill in altitude option.

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hmm nice. I don`t know it before, but one NMEA sentence contain difference between ellipsoid and geoid. So I`ll try to implement it ..


about usage of offline DEM data, create for this separate topic please


EDIT: I have checked altitude from internal GPS on nivelation point, and data are already improved by difference between geoid and ellipsoid. So no need for this settings as I see

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Try this function inside OruxMap. In my case: Locus from net 105; topo map 1:10000 103m; Aster (from GetAltitiude app) 106m; Gps on Android 128, oruxmap with correction 109m. Garmin Dem 106m. So... Try thid function inside Orux.

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I noticed NMEA correction settings in last version but it doesn`t work. I try and still I have displays and record not corrected value. I compared it to (I hope) similar settings in OruxMap and in this app it work. It it`s not perfect but instead of 130m I have 98 when real altitude is ca. 105.

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ah sorry, problem on my side. Check next version please and let me know

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Hello Menion,


in 2.0 still the same. Maybe correction works but doesn`t show corrected value. I tried and compared with Orux where correction change altitude.

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I have checked it before 2.0.1 version and it works correctly for me on Nexus. When this feature is disabled (in settings), I see home around 280m, When I enable it, I see in GPS screen (for example) 240m. Reality is around 235m.


What device do you use? Official rom? Because for example on Motorola Xoom, there are no NMEA messages from GPS. Don`t know why, but they don`t come. Also check if you have this enabled in settings

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I have HTC Desire HD (unbranded) with official Lite Gingerbread 2.3 from XDA. NMEA in Orux works on phone without a problem.

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I made some test on HTC Wildfire (Adroid 2.2) and Defy+ (2.3). It dosn`t work. So it isn`t a problem of smartphone / OS because correction in Orux works well but in Locus not.

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NMEA correction works for me (SGS II, 2.3.6, Locus 2.0.1), typically without correction the hight is reported about 40-50m too high whereas with enabled correction it`s only about 10m too high.

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So... why not work on HTC HD, Wildfire, Sensation and Motorola Defy+? Where Orux correction works? And in Orux difference beetween real and GPS alt after correction i between -10/+10 m. So definitely better then without correction.

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Menion, I now tried to record a track with switched on NMEA and altitude filter ultra heavy.


Prior to start of the recording I saw on the display a NMEA corrected altitude of about 470m, then I started the recording and put the phone into my jacket (so I didn`t see what acually happened) but later on the recorded track I can see that altitude was going down dramatically though my track started on almost flat terrain. After short time the alitude reached 48m (not 480m!) and did not change anymore though I crossed some hills (the whole track I guess was in an altitude range of 460-520m)


Shortly before I stopped the recording, I disabled the altitude filter and also NMEA correction and the reported altitude immediately changed to about 500m. Switching on NMEA resulted again in a completely wrong and to low altitude.


However switching GPS off/on made the NMEA correction working again (not contained in the track).


I observed this now two times. I didn`t yet successfully record a track with meaningful NMEA corrected altitude.


I`ve put nmea and gpx to locus_dev/_temp/tommi/.


I used Locus Pro 2.0.1.


Hope this helps. Possibly this goes in the same direction as the problem of pajaku.


Thanks.

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thanks Tommi and also Pajaku. Before next release (probably on weekend) I`ll focus on this. This topic is going to be too old and still not yet solved, damn ..

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Menion, fyi: I just tried NMEA correction on SGS I with Locus Free 2.0.1: there it doesn`t change the altitude at all.

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fine, I probably found issue that may cause problem but because on all my devices it worked before, I need some more test. Tommi you have access to dropbox, anyway pajaku, may you send me your email address that you use on dropbox? I`ll send you invitation to shared folder with testing version and if you`ll have some free time, you may test new version (I`ll place it there after a while ...)

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I`ll send my email on Locus address.

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Menion, I tested the 2.0.1.4 now for 1/2h. Up to now I wasn`t able to reproduce the problem with my SGS II, the altitude stays corrected now. However, I don`t know exactly how to trigger the problem, so I can`t be sure.


On the SGS I (Android 2.3.3) there was no improvement with 2.0.1.4.

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Thanks Tommi ...


I`m quite confused ...


To correct altitude by NMEA data, I need these NMEA data. But I discovered that on my Xoom device, these messages aren`t received. It should be similar on your other phones.


Simply install this application https://market.android.com/details?id... and check if you`ll see these messages. If so, NMEA altitude correction in Locus will work. Why I`m confused is because you talk about correction in Orux. So I installed it and tried and seems to work also on Xoom, so I really don`t know how he`s do it :).

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Menion, bad (SGSII) and strange (SGSI) news from my side:


SGS II: today I did again 2 recordings. One with car almost 2h long which worked quite well but at the very end, when I parked my car in the garage there are 2 points in the track with a completely wrong altitude though longitude/latitude is o.k.


The other recording was on a walk, altitude in the first few minutes of the track was o.k., but then suddenly, under clear sky, altitude dropped to about 50m and didn`t recover.


I`ve put both tracks together with NMEA data to locus_dev/_temp/tommi/.


SGSI (Android 2.3.3): Still shows no corrected NMEA. However I installed "NMEA Recorder" App and this shows a value antenna_altitude_abovebelow_mean_sea_level of ~490m which is more accurate than the value Locus 2.0.1.4 reports (~530m).


On my SGSII NMEA Recorder and Locus show the same value.


Seems NMEA is available on SGSI but Locus can`t interpret it (similar to Panjaku`s results).

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Recorder works on my HTC without problems.

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guys, I`m changing name of this topic. For some (unknown) reasons it`s causing me more troubles. And mainly, I found better solution ;)


Right now I implemented compute of geiod height from geoid model directly in Locus, so I`ll improve settings a little and place some testing version on dropbox later.

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I test today latest version from Adroid Market ad it looks like correction finally works!

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it works? damn ... forget on it, really :) I have working much better solution over global geoid model. It works on all devices and without any issues ...

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Yes... I tested few hours ago: No correction 138, correction 102, dem alt 106 m...

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On Topo map 1:10000 ca. 104 so not too bad,

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pajaku, new version on dropbox. Suggest to look to menu > settings > GPS > altitude correction (mainly automatic correction)

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Hello,


I tried to get NMEA data with internal GPS of my Defy+. No chance :-(


With external GPS Mouse (Jentro BT-8) it works.


@pajaku: Did you get NMEA run on Defy+ with internal GPS?

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Official release from market doesn`t work on Defy+ but works on Desire HD. I didn`t try beta on Defy.

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Newest realise works great on Defy+ too.

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perfect, thanks. Anyway I suggest to use "Automatic correction" that calculate Geoid height from Global Geoid model. Enough precise for phone needs ...

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