Altitude mismatch.

acvdmolen

In launcher settings I have selected the kompass.
The height or alltitude gives me between 55 and 60 meters that's in my case about 55 to 57 meters to high. In real I live at 3 meters above sea level.
Is there a way to correct it?

DUDU-Meng

acvdmolen
How did you arrive at the figure of 3 meters?

acvdmolen

DUDU-Meng that's my correct altitude 3 meters above sea level measured with professional gps equipment and that is how it is also geographical written.

grenoblours

The same problem for me and many more in the forum. Dudu7 gives a wrong altitude 50 meters above the correct one (either with the gps antenna included with the kit or the OEM GPS car antenna).
My garmin watch gives the correct altitude (i.e. the actual one, found on any geographic map and on the sign posts on the street), the OEM Citroen RT6 head unit as well.
There is Something wrong in the way that Dudu7 hardware / software handles altitude informations.

acvdmolen

grenoblours that's correct I have post it an half year ago also. Because I travel al lot in Europe I like to see the correct altitude wich is important for my work.

DUDU-Meng

grenoblours

acvdmolen
Can everyone install an app on DUDU that you feel is more professional and can display altitude, to compare whether it shows the same value as DUDU or also differs by 50 meters?

DUDU-Meng

Okay, let's verify this issue.

grenoblours

DUDU-Meng
First of all, for reference, I live in France / Europe in a valley surrounded by mountain ranges. The actual altitude of my place is 222 meters above sea level.
So I installed several apps from Google Play Store :

Altimeter (https://play.google.com/store/apps/details?id=com.exatools.altimeter)
GPS Test (https://play.google.com/store/apps/details?id=com.chartcross.gpstest)
OsmAnd (https://play.google.com/store/apps/details?id=net.osmand)

All of these apps, included the GPS test app installed by default (and the status bar as well), display the wrong altitude (around 270 m).

But I think I know where the problem would be : The head unit handle raw datas from the GPS satellites; then, some apps need the exact location in order to display the correct altitude; I guess the apps check or download an altitude data base according to the exact location. The "GPS Test" from play store has an option (under altitude settings : Use Geoid) that when enabled displays the exact altitude. Unfortunately, the correction of altitude is managed only by this app, the altitude displayed on the status bar is still wrong.

I hope it can help.

Mikescotland

grenoblours so it looks like gps firmware of the headunit (not apps) adds 50 m roughly. Problem with the gps unit driver.

grenoblours

Mikescotland
Actually, the head unit Dudu7 is kind of "right". For comparison purposes, I installed the same GPS apps on my mobile phone than the head unit, and it appears that raw datas altitude from GPS are wrong as well; the difference in the mobile apps, the app displays both altitude (raw and corrected).

Example : In this screenshot from the GPS app installed on my Samsung S25+, the actual and almost correct altitude is 215,9 m (MSL), the other one (266,6 m) seems to be the raw data from the GPS chip.

Mikescotland

grenoblours just measured on the map for my location and it's 61 m. Dudu shows in gps test app 58 m.
Looks like it's right after all as well. Compared with my phone as well and discrepancy is 2m which is nothing.

DUDU-Meng

grenoblours

Mikescotland
We also consulted some reference materials. In Europe, special corrections are required to calculate the actual altitude, and the original GPS altitude is 50 meters higher than the actual value.
We are also researching methods.

surfer63

Please read my reply from Dec 7, 2024.
https://forum.dudu-auto.com/d/628-altitude-measerment-difference/3

Mikescotland

surfer63 ah I see what you mean. Dudu does not apply Geoid to the widget value.
I've got:

Dudu 82m
gps test 84 m
gps test with Geoid 32 m
altitude map for my street is 35 m

So yeah. @DUDU-Meng I hope this clarifies.

Mikescotland

DUDU-Meng not only in Europe and it varies between the areas of Europe.
There must be a Geoid file available because gpstest has this option built in.

But, I'd say, it's a very low priority bug. Haven't had any reason to look at altitude so far for any useful purpose.. Other users might.

acvdmolen

Mikescotland that's what I mean, the raw and correct data. @ dudu-Meng Apps which are used for navigation with correct/real altitude measurement use files like europe.dem afrika.dem enz. to correct raw data to real altitude levels.

Regards,
Arjen

DUDU-Meng

acvdmolen
Yes, we are also reviewing the relevant information and doing our best to resolve the issue. If there are any test files, I will post them here for everyone to help test.

DahTank

I would like to add that i am in Thailand and the Altitude readings are also about -50

I can provide Altitude readings from my iPhone vs the Dudu7 headunit for reference if needed

acvdmolen

Here you see the difference between raw and real after correction through dem altitude/elevation data which is the real alltitude.