Hslm wrong

[80marcophotoscan]

Hi,
when i have finished to create the dem i can see the hslm for any point in the dem...
i have compared my dem with google and the hslm for the same point doesn 't mathce...

Any ideas ?

[stihl]

Hi,

Where are you from and what does 'hslm' mean? I assume you mean height or elevation.

There could be numerous reasons why there's a difference between your DEM elevation and an elevation shown on Google Earth or Maps.

Is the Chunk geo-referenced? Do you have GCPs or camera positions?

[Dave Martin]

Marco,

By "hslm" do you mean Height above Mean Sea Level ?  If so that will add another datum to be added into the mix. We need more info as Stihl has suggested.

[80marcophotoscan]

Hi...
Thanks
I m from sardina
I have a PHANTOM 3 advanced and every photo was taken with gps coordinate....

yes hslm is that you mean...

i do these:
import photo
alligned
dense cloud
mesh
create dem
create ortophoto
export dem
export photo
analize all with qgis and the hslm is not the same on google earth...

stop i don't make other....

help pleaseee

[Alexey Pasumansky]

Hello 80marcophotoscan,

Phantom 3 might be writing height above the take off point to the image EXIF. While PhotoScan expects that altitude is specified above the ellipsoid (unless you are using compunt coordinate system with the different vertical datum).

[80marcophotoscan]

Hello 80marcophotoscan,

Phantom 3 might be writing height above the take off point to the image EXIF. While PhotoScan expects that altitude is specified above the ellipsoid (unless you are using compunt coordinate system with the different vertical datum).

what have i to do for my problem ??

[Alexey Pasumansky]

Hello 80marcophotoscan,

I think that you need to get proper altitude values from the DJI log. There might be Relative altitude value written to the XMP profile of the image header, that may be more reliable than Absolute altitude written to EXIF, then add the altitude above ellipsoid for the take-off point for every camera height (Relative altitude) - it will give more or less correct values for the camera heights above ellipsoid.

However, note that Google Earth is showing altitude above mean sea level.

[80marcophotoscan]

to do that you say...have i to calibrate the compass first starting a new work on the new location or what have i to do ?