DDS/BIL plugin script for sub-meter elevation

[Akimh]

Hello kaktus40, I was wondering how you can alter your script to use sub-meter elevation ranges. I assume, your using the int 16 bit value range. It's working great with data of elevation ranges in meters using the dds/bil plugin and your GeoserverTerrainProvider plugin. Now, I'm trying to include data of sub-meter elevation ranges (e.g. 0.3m). I created floating 32 bit tiles and altered your script to set and get float32 values of your dds/bil plugin script. Also, I set the byte order in GeoServer to "Big Endian" which causes the error(see picture).

Do you have any ideas?

Thank you!

[kaktus40]

Hello can I have a sample of your data? I'll work with it and make an update of the plug in.

[Akimh]

Hello, and thanks for your support. I share it with you in Google Drive. You should see a notification in your Gmail.

[kaktus40]

Hello, I worked with your sample. My stages:

• I resampled ex2_dsm.tif and ex2_transparent_mosaic_group1.tif in order todisplay in EPSG:4326

gdalwarp -t_srs "EPSG:4326" -ot Byte -co "TILED=YES" -co "COMPRESS=DEFLATE" -r cubicspline ex2_transparent_mosaic_group1.tif converted
gdalwarp -t_srs "EPSG:4326" -ot Float32 -co "TILED=YES" -co "COMPRESS=DEFLATE" -r cubicspline ex2_dsm.tif converted2

• I generated two pyramids

gdal_retile.py -v -r cubicspline -ot Float32   -levels 6 -ps 2048 2048 -co "TILED=YES" -co "COMPRESS=DEFLATE" -co "ZLEVEL=5" -targetDir pyramid2/ converted2
gdal_retile.py -v -r cubicspline -ot Byte   -levels 6 -ps 2048 2048 -co "TILED=YES" -co "COMPRESS=DEFLATE" -co "ZLEVEL=5" -targetDir pyramid/ converted

• In geoserver for theelevation data, I configured "BIL Format Settings" with the following parameters:
  • Default Encoding : application/bil32
  • Byte Order : Big Endian
• For the terrainProvider, I used the following code:

terrainProvider = new Cesium.GeoserverTerrainProvider({
                url : 'http://localhost:8090/geoserver/ows',
                 layerName: 'elevation:evaluation',
                 maxLevel: 20,
                 service: "WMS",
                 formatArray: {
                            format: "image/bil",
                            postProcessArray: function(bufferIn, size, highest, lowest, offset) {
                                var resultat;
                                var viewerIn = new DataView(bufferIn);
                                var littleEndianBuffer = new ArrayBuffer(size.height * size.width * 4);
                                var viewerOut = new DataView(littleEndianBuffer);
                                if (littleEndianBuffer.byteLength === bufferIn.byteLength) {
                                    var temp, goodCell = 0,
                                        somme = 0;
                                    for (var i = 0; i < littleEndianBuffer.byteLength; i += 4) {
                                        temp = viewerIn.getFloat32(i, false) - offset;
                                        if (temp > lowest && temp < highest) {
// needed for big Endian 
                                            viewerOut.setFloat32(i, temp, true);
//for little Endian, there is no need to switch byte so the code should be  viewerOut.setFloat32(i, temp, false);
                                            somme += temp;
                                            goodCell++;
                                        } else {
                                            var val = (goodCell == 0 ? 1 : somme / goodCell);
// needed for big Endian
                                            viewerOut.setFloat32(i, val, true);
//for little Endian, there is no need to switch byte so the code should be  viewerOut.setFloat32(i, val, false);
                                        }
                                    }
                                    resultat = new Float32Array(littleEndianBuffer);
                                }
                                return resultat;
                            }
                        }
            });

//place camera to the correct position
 var target = Cesium.Cartesian3.fromDegrees(6.68093, 46.55159, 1000);
    var offset = new Cesium.HeadingPitchRange(0, -Math.PI/2, 300);
    viewer.camera.lookAt(target, offset);
    viewer.camera.lookAtTransform(Cesium.Matrix4.IDENTITY);

The results are in the attached images.

Comments: Initially I was worried that the warping of the data creates some artefact but by using bing imagery, it seems correct. The artefacts seems to be the pick of trees!!

Initial position with your imagery

an other position

with bing

with bing

with bing

[Akimh]

You're amazing. Thank you very much. Here is my result:

When I move around I experience a couple of artifacts.

When I include the Bing base layer (with or without the UAV imagery layer), I observed this behavior.

Is there a workaround, since your examples look like fine?

Also, when I'm zoomed in, I can barely move around (very slow). I assume, this is a performance issue (data size, etc.).

Again, thank you for your great support.

[kaktus40]

well a workaround should be to merge the elevation data in order to have a bigger area. The artefacts comes from a rupture in elevation data: the area from sample have an elevation of 800m and the rest of the world is at 0 m...

[Akimh]

That make sense. When I have only a small sample area, how do I merge with other terrain data to provide a bigger elevation area? Ty

[kaktus40]

you should see gdalbuildvrt to make a virtual file. After you can use the vrt file as a tif with gdal_retile

[Akimh]

Just two final questions:

I'm just wondering how you draped the elevation over the globe. Based on the sample screenshot above (especially the first one) , the rest of the globe is flat (outside the sample area) and is floating nicely into that area. It doesn't look like that you extended the area of the elevation data?.

I see also that you can successfully include the Bing layer and the custom image layer together. I can only see my custom layer when I try to include both.

Thanks again for your great support and of course the time your spending.

[kaktus40]

Hello, for the first question it's the good assertion, I just put a pyramid data elevation based on your sample. When I saw the data via open layer embedded in geoserver, the area around your sample is completed with no data value. I don't see your second question.

[Akimh]

Hi, the no data value of my sample is -1000 meter in the GeoServer OpenLayer viewer. I'm sorry, but I cannot follow your steps to create a nice transition between the elevation data and the rest of the globe. I altered the no data value to e.g. 780 meters and 0, but that seems to be not working. What do I miss?

My second question was, that you included successfully the Bing layer and the custom image layer together, which looks nice. I can only see my custom layer when I try to include both. (see following screenshot, no Bing imagery visible )

Thank you for your time.

[Akimh]

Hello, I solved question two by leaving out the BingMapsImageryProvider in the Cesium.Viewer constructor.

[kaktus40]

All my scripts are above. I didn't change the nodata value of your sample.

[Akimh]

Thanks kaktus. I got it.

Since I try different methods to integrate elevation data into Cesium, I saw that you also forked the gdal2cesium python script from giohappy. Did you get it to work in a windows system?

[kaktus40]

for now I didn't work on it

[Akimh]

Thanks for all of your support.