Self intersecting polygons after import into Google Earth - kml

There are some unexpected artifacts when importing the merged polygons ("dissolve all" function in QGIS) into Google Earth as KML or SHP.
I also tried merging the polygons using the C# Clipper library, but exactly the same result.
Polygons before "dissolve all"
Result in QGIS:
This is how it looks in Google Earth:
It seems like the problem in Google Earth is caused by self-intersecting polygons.
Update: When I ran "Geometry Tools > Simplify Geometries" in QGIS it fixed the self-intersecting polygons somehow. In the results it said it simplified from 78319 points to 76322, but it is still unclear what it actually changed.

Looking at your images it appears you haven't transformed the projection of your data. (the circles are more perfect in google earth and is more elliptical in your QGIS image). Try to re project your data to WGS84

Related

Custom drawing rotated SVG to Leaflet map

I am using leaflet 1.7.1 and I need to put custom markers on map.
I am currently using circles (as in: L.circle([lat, lon], {radius: rad}).addTo(map);) as my markers (note radius is significant and should be in meters).
Now I need to add a "direction" to this circle essentially displaying something like:
I actually need to implement some L.directedCircle([lat, lon], {radius: rad, heading=45}).addTo(map);, but I don't know how to do that.
I also tried looking for plugins, but nothing seems to do what I need.
Note that the image above is just an example, I'm open to other options but that seems very simple (it's just a 4-points SVG poliline) and effective.
If that matters I'm using leaflet through pyqtlet2, but I'm prepared to "get my hands dirty" using directly javascript.
Any help appreciated.

How does Revit Analysis Display "Show Contour" work?

I am not sure if "ShowContourLines" property of
AnalysisDisplayColoredSurfaceSettings class in Revit works as expected.
I am expecting contours similar to isolines to be displayed but instead the outline
of the surface is highlighted.
Has any one got similar experience or know more about this feature?
I have not used the ShowContourLines property, but here are some other samples using AnalysisDisplayColoredSurfaceSettings that may be of use:
Display Webcam Image on Building Element Face
AVF Displays Intersections and Highlights Rooms
Apollonian Sphere Packing via Web Service and AVF
Intersect Solid Filter, AVF vs DirectShape Debugging

Convert a Google Earth kml to a Google maps kml - Using image overlays

I have created a kml file with Google Earth that creates an overlay using an external image. It works well, and I would like to find a reasonably convenient way of converting the kml so that Google Maps can read it and display it in a similar fashion.
Google Maps cannot process Google Earth coordinates, so I attempted to convert them myself. For instance I replaced the Earth Coordinates:
<gx:LatLonQuad>
<coordinates>
-80.34344837780532,33.1105864538138,0
-80.31934785561177,33.09410014458361,0
-80.30034967982111,33.11373571527255,0
-80.32473786478347,33.13044135685429,0
</coordinates>
</gx:LatLonQuad>
with the equivalent Maps coordinates:
<LatLonBox>
<north>33.13044135685429</north>
<south>33.11373571527255</south>
<east>-80.31934785561177</east>
<west>-80.34344837780532</west>
</LatLonBox>
Unfortunately, the are not exactly "equivalent". The Maps overlay is slightly off and rotated incorrectly.
Here are the images from the two:
Earth Example
Maps Example
I can see why it doesn't work, but I'm at a loss as to another solution. Anyone know of a simple way to convert a Google Earth kml to a Google Maps kml when an image overlay is involved?
Per the KML reference a <LatLonBox> also has a rotation. Not sure if that is supported for Google Maps, but it should address the issue you are having. The <gx:LatLonQuad> allows you do specify a rotated box (which is what you are doing), this is what that specifies:
http://www.geocodezip.com/geoxml3_test/v3_geoxml3_kmltest_linktoB.html?filename=http://www.geocodezip.com/geoxml3_test/GoogleEarthPolygon.kml
According to the KML reference for Google Maps, LatLonBox is supported, rotation is not:
KML Element Supported in Google Maps?
<LatLonBox> yes
<rotation> no
therefore you need to make your overlay align on north/south east/west boundaries (a non-rotated LatLonBox) to work on Google Maps.
You have a problem with your computed LatLonBox (the small blue box), you want the green box:
http://www.geocodezip.com/v3_GoogleEx_layer-kml_linktoB.html?filename=http://www.geocodezip.com/geoxml3_test/GoogleEarthPolygonA.kml
I think the only way to fix this is to take your original image rotate it and save an image aligned on north/south east/west boundaries that fits in the bigger box.
Either that or make a custom overlay that supports rotation somehow.

ALTITUDE_CLAMP_TO_GROUND error in GE 7.0.1.8244

I think I have found an error in GE V7.0.1.8244. I create a KML route file and display it with setAltitudeMode set to ALTITUDE_CLAMP_TO_GROUND. In GE V6.2.2.6613 it displays correctly but in V7.0.1.8244 (currently beta) it does not. Same program source, same data. See attached image here:
.
Any ideas anybody other than installing an other version of GE?
This is clearly a bug in GE 7.0. A few of the elements in the KML test file are out of order but nothing to cause this problem. Even if you drop the altitude values and change altitudeMode to relativeToGround it gets worse not better. Neither DirectX or OpenGL mode makes a difference.
You can report the issue here to get any updates on the problem:
http://code.google.com/p/earth-issues/issues/list
Might be an error in elevation data. You can also see this error in the sample line example if you zoom close to the path.
Only short-term fix is reverting back to GE 6.2.2 if want to view this KML correctly, otherwise, wait for a fix.
UPDATE: Issue in Google Earth issue tracker can be found here.
It does look like a bug, rather than down grading though you could look to use one of the Google Earth extensions - specifically the gx:altitudeOffset element. From the docs...
A KML extension, in the Google extension namespace, that modifies how
the altitude values are rendered. This offset allows you to move an
entire LinearRing up or down as a unit without modifying all the
individual coordinate values that make up the LinearRing. (Although
the LinearRing is displayed using the altitude offset value, the
original altitude values are preserved in the KML file.) Units are in
meters.
This should allow you to raise the path by a meter so that the clipping doesn't occur.
It is also worth noting that...
In Google Earth, a Polygon with an of clampToGround
follows lines of constant bearing; however, a LinearRing (by itself)
with an of clampToGround follows great circle lines.
So perhaps you need to adjust your path to account for this discrepancy?

Stop dimming / color change of overlapping placemarks on Google Earth

I'm using Google Earth to display point data as placemarks. The data is on a color-coded scale, and so it's pretty important that they keep their colors (which are set via a series of differently colored icons)
However, Google Earth seems to have a 'feature' whereby it dims some placemarks if they overlap. I can find no reference to this feature, nor any way to avoid it, turn it off, using KML or otherwise.
The question was originally asked here:
https://groups.google.com/a/googleproductforums.com/forum/#!topic/earth/DTl6yGLvPvw
Where there are also screenshots of the problem.
Thanks!

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