Google Earth Polygon surface area to follow the curvature of the earth model

Question

Question: When drawing a polygon in Google Earth with latitude, longitude and elevation values at each node, how do you ensure that the surface area of the polygon also represents the desired elevation in relation to the earth's surface (interpolated between the nodes)? And, not have the surface area tangent to the nodes.

At the moment, when I draw a polygon over the earth at 800000 m absolute, it looks like this:

I would like the surface to be the same height as the perimeter of the polygon or to have the surface interpolated between the nodes. So, for example, if I had an inclined plane stretching over the ground where one end is 50 m elevation absolute and the other end is 500 m elevation absolute, the area enclosed in the polygon would represent the interpolated z value. At the moment, it is clearly not the case as can be seen in the picture.

I suspect it would be a setting in Google Earth or there is something in the KML code that can be manipulated..

Answer 1

Currently, it is forcing the polygon to draw at an absolute elevation (looks to be above sea floor?) You can clamp it to the surface, which will essentially 'drape' it over your elevation / DEM. To fix the issue the KML syntax is

<altitudeMode>clampToGround</altitudeMode>

If you could post some of your raw code, might be able to help with implementing it, but this is the best I can come up with without seeing the raw code.

Answer 2

The way I approached this problem is quite laborious using csv files but I'm working on a quick method using Python.

If you have the csv file with three columns being lat, long and z, open it up in a text editor, just copy and paste it into the kml between the coordinate tags.

If your data is not in wgs84 (lats, longs, z), the it's just a matter of reprojecting in gis, appending coordinate data to to the layer and save it as csv. Easy but time consuming.

Answer 3

I've solved this issue now. I've created a python script that generates little shapes with 4 sides each side having x length. I can set x = input() e.g. x = 100 metres. The surface area enclosed in the extents of a large polygon now has much greater accuracy re. representing absolute height relative to the earth's shape. I'm able to generate a polygon given some data inputs, by generating tens of thousands nodes to make thousands of squares in a maximum of 10 seconds and have it auto-open in Google Earth. Say a shape is I = 2400 wide and J = 15000 long. The whole polygon is modeled by a series of lines running in I and J directions (generally running across each other but not necessarily perpendicular to each other). e.g.

x = 100
i = I/x
j = J/x

Then it's just a matter of running a loop to trace this shape:

shapeTracer = [
[1,1,2,2,1], #i lines
[1,2,2,1,1]  #j lines
]

thus creating complete squares that enable GoogleEarth to create polygons. Note that once a little polygon is generated, a new little polygon must be created, which would be something like:

shapeTracer = [
[1,1,2,2,1], #i lines
[2,3,3,2,2]  #j lines
]

and so on.

I'm guessing this idea can be applied to generating all kinds of shapes such that the area inside a polygon represents accurate height so the other code will need to be written as appropriate. If anyone has a better way of achieving the same goal, please I would love to know about it. If anyone is interested in knowing more about what I've done, please ask :-)

Answer 4

Simple just use spheres formula and you will got the estimated land mass of particular area on earth from centre of earth's So you compared specific gravity of that area and Also the forces experienced by that area due to rotation of earth Now by this we calculate moment of that part of earth's according to fault lines of earth's and found the next earthquake date All the worldwide science foundation are challenged against this technology