Thanks TIG. I slept on it, and your answer this morning made a lot of sense.

I'm an occasional user of Sketchup, and I have just created a new model. In a previous model, I was able to selectively display parts of the model, and associate the each selection with a scene. I've just tried to do this again, and my scene names are shown in parentheses, and when I click on the tab, there is no change in the display.

Can anyone explain what's going on?

This is the first time I've tried to build a model from a photo, and I don't know whether that has made a difference.

Peter

I seem to have determined the units of the ModelTranslation values - inches.

My problem now is to reset the z-axis of the model to make it easier to calculate elevations. For instance, I want to show the impact of a flood which reached a certain height. That height is given in AHD (Australian Height Datum) relative values. I presume that the location data elevations are also AHD-relative. I can represent a flood by drawing a rectangle centred on 0,0,0 and pulling the surface up to the height of the flood. The idea works well, apart from some apparent inaccuracies in the terrain data.

However, it is far easier to simply pull the "water" to a given height in metres, than to convert the height to inches, subtract the Z translation in inches, then reconvert the difference to metres to calculate a level relative to 0,0,0 to pull to.

Flood level

Thanks Chris.

It looks like UTM. The 7070Km would be a northing, which in the southern hemisphere is relative to a point 10,000km south of the equator, and the origin of the easting is a point 500km west of the zone central meridian. Therefor the central meridian is at an easting of 500km. The zone can be determined from the longitude and latitude; in my case 56J. So those values are in inches.

That leaves the ZValueCentered field. All I can saw is that it generally corresponds to the ModelTranslationZ value, so it is in inches and represents an elevation. When and why it changes from the translation value I have no idea.

Thanks again. Now all I need to do is work out a way to translate the location information on the architectural drawings into UTM coordinates.

Peter

I'm trying to get some information about the geo-location fields ModelTranslationX, ModelTranslationY, ModelTranslationZ and ZValueCentered.

I want to try to place a model according to architectural drawings which give the elevations in RL - reduced level - which is a value "reduced" from the nominal sea level. I don't know much about these things, as you will soon gather.

I can grab the terrain from Google Maps (or Earth) within SketchUp 8, and when I look at the dictionaries in the ruby console, I see longitude and latitude, and the values mentioned above. I assume that these values represent the origin of the model.

What are the units, and what, exactly, is the meaning of each of these values?

If I grab a square of water off a beach, I find that the ModelTranslationZ and ZValueCentred values are -0.0, as I had hoped. If, then, the Z values are elevations, the most sensible unit I can find for them is inches. If I convert the value to metres, I get a sensible (though negative) value for Z in an area near where I live. However, when I convert the X and Y values for a region n the near north coast of Queensland (Latitude = -26.459146 Longitude = 152.989157) the values (X -19642484.6811491 Y -278482951.898236) translate into approx 500km and 7070km respectively. 7070 /might/ get to the date line, but 500km?

Can anyone make sense of these values?