Emlid UAV ppk processing out put problem


everyone i have fixed wing uav with reach m+ as a rover reach rs+ as a base. camear sony a6000 for triggering am using seagull map2, in m+ am using hotsho cable, when am doing mapping am flying 20 m/s in auto grid in terrain mode. my base is unknown ponit. After flying data to be processed in rtklib am flying 190m from the ground. but my actual elevation is from sea level 252m to 300m but it is showing after processed. above 400+m. am reducing flying altitude from my output elevation value it is showing correct, but when am doing image processing my DEM showing wrong elevation,

so please anyone help me out this problem, whether my setting, problem or processing problem in rtklib

Hi Tamil,

It seems that you’re comparing ellipsoidal and orthometric heights.

but my actual elevation is from sea level 252m to 300m but it is showing after processed.

If the height is measured from sea level, it’s called orthometric.

When you process logs in RTKLib, you receive ellipsoidal heights above the WGS84 ellipsoid. So, you need to convert these heights to the required coordinate system.

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actually my out put elevation hight is ellipsoidal only. so i need to convert wgs84 to orthometric . even i have doubut why m+ giving this kind of values. i checked which placed i fly on google earth it is showing minimum 250 to 300m hight. my output showing 400+ if i subtract my flying altitude, i get it google earth value.

Google shows MSL not elipsoid.

so if want to get msl value means what i have to do. i need to convert

What vertical datum are used in your country? What does your client require?

Mean see leval (MSL)

What is the epsg code in use for MSL in your country?

WGS 84 / Madhya Pradesh - EPSG :7766

That’s a 2D system, only covering X and Y. https://epsg.io/7766

What does your local state authority use for MSL?

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Hi Tamil,

I agree with Christian. Google Maps show orthometric height above the global geoid. The global geoid is referred to the average level of the World Ocean. I suppose this is not what you need.

So, to get orthometric heights used in your country, we need to know which geoid is used in your country.