Geolocate KMZ - wrong altitude in Sketchup Pro but correct in Google Earth

Hi,
I am trying to import a kmz file and get it to geolocate correctly. So far it is working in GoogleEarth, but not in Sketchup, were the altitude is off by about 70 meters (model is flying above terrain). Horizontal placement is correct though. Is it possible for Sketchup to “read” the altitude in the file like GoogleEarth does?

/Sabina

Hi Sabina,
SketchUp’s importer does take the KML altitude into account.

But merging two locatable things (SketchUp model and imported file) requires that both have a complete georeference. If your model is only geo-located in 2 dimensions (latitude, longitude) and has a missing altitude, there is no reference to which the imported KML’s altitude can be related to.

This can happen if:

  • You located the model manually by writing the coordinates in Model Info → Geo-location
  • You located the model by importing terrain (File → Geo-location → Add Location), but you use a version of SketchUp other than 2017+ Pro without access to elevation data. (Elevation data is usually not available for free; even Google’s terrain data is not free and Google does not make it available to SketchUp for free.)
    See this: https://help.sketchup.com/en/faq-add-location-changes-sketchup
    • In that case, you can update to a SketchUp Pro subscription.
    • Or you can import accurate terrain from another terrain provider like Oob Terrain.
  • Or (in SketchUp Pro 2017+) no terrain data is available for your area or one of both elevations is not accurate. Elevation points can regionally be at a very sparse grid (like 90m) and I once found the Google Earth grid to be offset by one grid unit, which caused a similar discrepancy.

Thank you for the reply Aerilius,

The imported KML file does include an tag and a value. Might be a case of missing terrain data for this area then… or that it isn’t accurate? Is it possible to check this somewere? In Modelinfo ->Geolocation I Could only find values for latitude and longitude for what I am guessing is my geolocated “grabbed” area?

  • Does your model show a terrain layer in the layers inspector (generated by SketchUp’s Add Location)?

  • To check whether the model has the correct geo-reference including altitude, you can use the extension Attribute Inspector.
    When clicking in empty space (selecting the model), The GeoReference dictionary must display the keys UsesGeoReferencing (true) and ModelTranslationZ.
    See also: Astrodynamically Correct Shadows at Altitudes Much Greater than Z=0

Yes, my model shows a terrain layer (also a Location snapshot layer and a layer0 were the imported model is placed).

UsesGeoreferencing has value: true and ModelTranslationZ has a float value about: -1939.71…

Try to edit the values, but can’t see that anything happens. Also move the model with move tool but values remain the same.

Also tried to import another model into Sketchup (this one also placed on the right location in Google Earth). Same result again; model is placed about 70 meters above the terrain layer.

A 3D file is imported as a component. Once positioned, a component won’t reposition automatically by changing the model’s attribute. But I would expect after editing the attribute, a newly imported geolocated KMZ file would be imported at a different location (?).

Maybe you have to keep the same value in ModelTranslationZ and ZValueCentered. It should be the offset in inch from the model’s origin to the normal height (sea level). If the component is 70m (2755.91 inch) above the terrain, I could imagine those two attributes should have the value -1939.71 - 2755.91 = -4695.62 (119 m altitude above sea level).

  • Does this match the value in the <altitude> field in the KML text file which is contained inside the KMZ zip file (e.g. when you open it in a file archiver like 7zip)?
  • If you then import the KMZ file again, does it appear above or below?

Hi again,

Thanks for taking time to figure this one out…
It seems the problem got solved by changing the value from negative to positive in the altitude tag in the KML file… in other words the definition of up and down on the z-axis is the inverted from Google Earth then. Tried it on a couple of models now and it consistently fix the problem.

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