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mesh from csv

J

jetta20162

Messages
88
Hi,

i have a large ascii csv (lat,lon,altitude) which i convert to a geotiff with gdal_grid -l layername layername.vrt layername.tif

the csv (example, altitude in meter):
x,y,z
14.21989837,50.87816992,326.79
14.21989837,50.87817920,326.79
14.21989837,50.87818848,326.79
14.21989837,50.87819776,326.79
14.21989837,50.87820704,327.56


the layername.vrt has the following structure:

<OGRVRTDataSource>
<OGRVRTLayer name="layername">
<SrcDataSource>layername.csv</SrcDataSource>
<GeometryType>wkbPoint</GeometryType>
<LayerSRS>WGS84</LayerSRS>
<GeometryField encoding="PointFromColumns" x="x" y="y" z="z"/>
</OGRVRTLayer>
</OGRVRTDataSource>

the tiff is not readable by resample.exe, opened with QGIS and saved again as geotiff.
Now resample.exe takes it and compiles a bgl. But the bgl just creates a hole in the existing mesh, like the altitude is 0m, but the terrain altitude is 340m.

the inf file looks like this:
[Source]
Type = GeoTIFF
Layer = Elevation
SourceDir = "C:\SBuilderX313\Tools\Work\layername"
SourceFile = "layername.tif"
MinValidValue = 0

[Destination]
DestDir = "Output"
DestBaseFileName = "layername_Elevations"
DestFileType = BGL
LOD = Auto

Is there anything wrong with my conversion? How would you create a mesh from a csv file?

Thanks for any suggestions
 
Perhaps one of the folks here such as Holger, rhumbaflappy, or Arno, that are more familiar with the work-flow required within QGIS GUI (or the rather arcane syntax for GDAL in 'command mode') ...could help explain the way to use that GIS application environment to ensure your XYZ ASCII data is interpreted and output as "elevation" for the 3rd "Z" field in each of your lines (records). :scratchch


I instead use Global Mapper, and in that GIS application, when such sequential ASCII (CSV='Comma Separated Values') text XYZ data is imported, one is automatically prompted with a configuration dialog in which the 3rd ("Z") field is assigned to be interpreted as "Elevation" / "Altitude".

Once that is processed and displayed in the default color HillShader mode on screen in the Global Mapper workspace, one can simply export as 3D "Elevation" data and choose the GeoTIFF (32-Bit Floating Point) output file format option.

IIUC, you are on the right track, but need specific GIS commands sent so proper GDAL / OGRE GIS tasks are performed on a XYZ file. :)

GaryGB
 
Last edited:
Hi,

Did you check the geotiff file you made in qgis? Do you see the right elevation there? And which data type (int, float, etc.) is used to store the data?
 
GaryGB said:
Perhaps one of the folks here such as Holger, rhumbaflappy, or Arno, that are more familiar with the work-flow required within QGIS GUI (or the rather arcane syntax for GDAL in 'command mode') ...could help explain the way to use that GIS application environment to ensure your XYZ ASCII data is interpreted and output as "elevation" for the 3rd "Z" field in each of your lines (records). :scratchch


I instead use Global Mapper, and in that GIS application, when such sequential ASCII (CSV='Comma Separated Values') text XYZ data is imported, one is automatically prompted with a configuration dialog in which the 3rd ("Z") field is assigned to be interpreted as "Elevation" / "Altitude".

Once that is processed and displayed in the default color HillShader mode on screen in the Global Mapper workspace, one can simply export as 3D "Elevation" data and choose the GeoTIFF (32-Bit Floating Point) output file format option.

IIUC, you are on the right track, but need specific GIS commands sent so proper GDAL / OGRE GIS tasks are performed on a XYZ file. :)

GaryGB
Click to expand...

Thanks Gary i will try global mapper.
 
arno said:
Hi,

Did you check the geotiff file you made in qgis? Do you see the right elevation there? And which data type (int, float, etc.) is used to store the data?
Click to expand...

Hi Arno, i checked the file with gdalinfo:

Driver: GTiff/GeoTIFF
Files: layername.tiff
Size is 256, 256
Coordinate System is:
GEOGCS["WGS 84",
DATUM["WGS_1984",
SPHEROID["WGS 84",6378137,298.257223563,
AUTHORITY["EPSG","7030"]],
AUTHORITY["EPSG","6326"]],
PRIMEM["Greenwich",0],
UNIT["degree",0.0174532925199433],
AUTHORITY["EPSG","4326"]]
Origin = (14.220059400000000,50.878201720000000)
Pixel Size = (0.000004840781250,0.000002863750000)
Metadata:
AREA_OR_POINT=Area
Image Structure Metadata:
INTERLEAVE=BAND
Corner Coordinates:
Upper Left ( 14.2200594, 50.8782017) ( 14d13'12.21"E, 50d52'41.53"N)
Lower Left ( 14.2200594, 50.8789348) ( 14d13'12.21"E, 50d52'44.17"N)
Upper Right ( 14.2212986, 50.8782017) ( 14d13'16.68"E, 50d52'41.53"N)
Lower Right ( 14.2212986, 50.8789348) ( 14d13'16.68"E, 50d52'44.17"N)
Center ( 14.2206790, 50.8785683) ( 14d13'14.44"E, 50d52'42.85"N)
Band 1 Block=256x4 Type=Float64, ColorInterp=Gray

The elevation in qgis looked right (~340m-380m).

Maybe some parameter is wrong or missing when i create the tiff using gdal_grid.
 
I would just try to add: SampleType = FLOAT64 to the source section of your INF file. I think by default it is assumed that the input data type is integer.
 
the mesh looks a little bit stretched. I used WGS84(EPSG:4326) projection inside the source data. Is FSX using the same or the WGS84 Pseudo Mercator(EPSG:3857)?

EDIT: just my mistake of retrieving the source data, now it is working
 
Hi terrain experts,

Please could someone point me in the right direction...i don't get it working. I tried global mapper, but the demo expired, and it is too expensive, so i tried to go only with GDAL. So far no problem, i use gdal_grid to create a geotiff from csv...here my problem starts:
which format i need to chose? I sometimes read resample.exe takes 16 bit integer, 32bit floating point...what do i need to use? After i produced the geotiff, resample tells me that pixel width and height must be greater then zero. I tried the tool GeoTiffToInf, but it tells me that the tiff has no geotiff-tags. The source file is a csv with "lat, long, elevation" data.

The output of gdal is as follows:

Code: 
gdal_grid.exe -ot UINT16 -of GTiff -txe 13.90594 13.90629 -tye 48.9353 48.93552 -l dem dem.vrt dem.tif
0...10...20...30...40...50...60...70..
gdalinfo.exe dem.tif -stats
Driver: GTiff/GeoTIFF
Files: dem.tif
Size is 256, 256
Coordinate System is:
GEOGCS["WGS 84",
    DATUM["WGS_1984",
        SPHEROID["WGS 84",6378137,298.257223563,
            AUTHORITY["EPSG","7030"]],
        AUTHORITY["EPSG","6326"]],
    PRIMEM["Greenwich",0],
    UNIT["degree",0.0174532925199433],
    AUTHORITY["EPSG","4326"]]
Origin = (13.905939999999999,48.935299999999998)
Pixel Size = (0.000014000000000,0.000008800000000)
Metadata:
  AREA_OR_POINT=Area
Image Structure Metadata:
  INTERLEAVE=BAND
Corner Coordinates:
Upper Left  (  13.9059400,  48.9353000) ( 13d54'21.38"E, 48d56' 7.08"N)
Lower Left  (  13.9059400,  48.9355200) ( 13d54'21.38"E, 48d56' 7.87"N)
Upper Right (  13.9062900,  48.9353000) ( 13d54'22.64"E, 48d56' 7.08"N)
Lower Right (  13.9062900,  48.9355200) ( 13d54'22.64"E, 48d56' 7.87"N)
Center      (  13.9061150,  48.9354100) ( 13d54'22.01"E, 48d56' 7.48"N)
Band 1 Block=265x265 Type=UInt16, ColorInterp=Gray
  Minimum=200.000, Maximum=201.000, Mean=200.741, StdDev=0.438
  Metadata:
    STATISTICS_MAXIMUM=201
    STATISTICS_MEAN=200.7408
    STATISTICS_MINIMUM=200
    STATISTICS_STDDEV=0.43819557277552


Has anyone a step by step guide to get csv->geotiff->bgl working with GDAL?

Thanks for any help!
 
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