Sketchup to KMZ location issues


I am doing a project for a client in which they want me to take structure locations spread over about 5 miles, add 3D models to each location point and export it to KMZ so they can use it for a Google Earth tour and flythrough for a presentation.

Here is my workflow so far:

  1. Took KMZ (structure location) points from client, imported into Arcmap as a feature class.

  2. Exported feature to DXF

  3. Imported DXF into sketchup (points come in as Cpoints)

  4. Find location in sketchup, and get maps and terrain for the entire project to ensure proper elevation and placement of structures.

  5. Drop cpoints to terrain and grow my structure components from cpoints using Raytracer extension. So, at this point, all structures should theoretically be in their correct place (at least on the x,y plane, the terrain is another story). Verified that structures are in correct place when compared to KMZ from client in Google Earth.

  6. Export 3D model to KMZ.

After opening KMZ in Google Earth, the structures start out in line with where they should be, but by the end of the line, they are at least 50 feet off of where they should be in Google Earth. This is obviously a big problem because the client needs these structures accurately placed. What is going on here?

This image shows where Sketchup says my model is placed (top view parallel projection)

This image shows where the model actually ends up when exported to KMZ. The point labeled 15e is the KMZ point from the client, and the little red dot is the test model (50 feet north of where Sketchup said it would be).

Any ideas on what is happening here? Thanks.

Looks like an issue with two different data sources that don’t agree. The KMZ file supplied by the client doesn’t aggree with location data provided by Digital Globe. There could also be cumulative precision errors induced with all the steps involved.

SU uses WGS84 as the datum while some use older datums and there can be a shift where the shift can be significant. The point does not actually move. just its mathematical lat , long etc it its particular datum so, make sure you are comparing apples and oranges.

That’s the weird thing though. After bringing in the DXF, I am not scaling the Cpoints at all, just aligning them very precisely where they need to be with the Digital Globe map in Sketchup, and the points are exactly where they are in the original KMZ in google earth. It is only after I export to KMZ and open in Google Earth that things are misaligned. Strange.

Do you have an idea of the pedigree of the data you are using? The two pics you show seem to indicate they were not taken widely time spaced but, there may very well be a number of conversion steps and different programs used in the work flow. The client may very well use auto-desk and the conversion to dxf is done some step by ??. Since you have zero info in your post addressing the issues raised by Dave and myself that at least has me at a loss to try and help any further. There are some free trials on the net you may try one of those and see if you get different results. I could not find any meta data on the two pics but may be not looking in the correct spot.:frowning:

Okay so they client gave us a KMZ of the points (pole locations).

I took that KMZ into Arcmap via KMZ to layer tool. Confirmed that the points had not changed position at all.

Exported points as DXF via convert to CAD tool. I have tried keeping the layer in WGS 84 system and projecting to UTM zone 12n (southern Arizona) before converting to DXF, both of which line up well when looking at it in Sketchup.

Placed point of origin on first pole location by entering the lat long of that point in the manual location dialog.

Snap first point to origin.

Add imagery and terrain in sketchup and confirm that the points line up with the basemap where I need them to be.

Place dummy poles at points and export to KMZ resulting in out of place poles.

I want to note that the poles get progressively more out of position as the line moves away from the origin. Hope this provides more information.

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