Unable to get a non flat terrain with SRTM

Hi All,

my config:
[osgEarth]  [Capabilities] Capabilities:
[osgEarth]  [Capabilities]   osgEarth Version:  3.1.0 build 100
[osgEarth]  [Capabilities]   OSG Version:       3.6.5
[osgEarth]  [Capabilities]   GDAL Version:      3.1.3
[osgEarth]  [Capabilities]   GEOS Version:      3.8.1
[osgEarth]  [Capabilities]   GPU Vendor:        NVIDIA Corporation
[osgEarth]  [Capabilities]   GPU Renderer:      GeForce RTX 2080 SUPER/PCIe/SSE2
[osgEarth]  [Capabilities]   GL/Driver Version: 4.6.0 NVIDIA 456.71
[osgEarth]  [Capabilities]   GL Core Profile:   no

Window 10 64bit

osgEarth comes from vcpgk.

I would like to use a large image as elevation source.
This a global mosaic SRTM image:

$ gdalinfo D:/data/LXSATLAB/SRTM/srtm.tif
Driver: GTiff/GeoTIFF
Files: D:/data/LXSATLAB/SRTM/srtm.tif
       D:/data/LXSATLAB/SRTM/srtm.tif.ovr
       D:/data/LXSATLAB/SRTM/srtm.tif.aux.xml
Size is 432001, 144001
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 = (-180.000833333333304,60.000000000000000)
Pixel Size = (0.000833333333300,-0.000833333333300)
Metadata:
  AREA_OR_POINT=Area
Image Structure Metadata:
  COMPRESSION=DEFLATE
  INTERLEAVE=BAND
Corner Coordinates:
Upper Left  (-180.0008333,  60.0000000) (180d 0' 3.00"W, 60d 0' 0.00"N)
Lower Left  (-180.0008333, -60.0008333) (180d 0' 3.00"W, 60d 0' 3.00"S)
Upper Right ( 180.0000000,  60.0000000) (180d 0' 0.00"E, 60d 0' 0.00"N)
Lower Right ( 180.0000000, -60.0008333) (180d 0' 0.00"E, 60d 0' 3.00"S)
Center      (  -0.0004167,  -0.0004167) (  0d 0' 1.50"W,  0d 0' 1.50"S)
Band 1 Block=256x256 Type=Int16, ColorInterp=Gray
  Min=-82.000 Max=7168.000
  Minimum=-82.000, Maximum=7168.000, Mean=645.220, StdDev=837.166
  NoData Value=-32768
  Overviews: 216001x72001, 108001x36001, 54001x18001, 27001x9001, 13501x4501, 6751x2251, 3376x1126, 1688x563
  Metadata:
    STATISTICS_MAXIMUM=7168
    STATISTICS_MEAN=645.22017458641
    STATISTICS_MINIMUM=-82
    STATISTICS_STDDEV=837.16640363713

My map file is really simple:

<Map name="ReadyMap">
  <sky_gl/>
  <GDALElevation name="SRTM">
    <url>D:/data/LXSATLAB/SRTM/srtm.tif</url>
  </GDALElevation>
</Map>

But the earth is desperately flat :



Other elevation sources work fine (tested with another local image and TMS based layer).

There is probably something wrong with my image (note it loads very fast in QGis thanks to overviews and displayed values are good) but i can't figure out what. This is a BIGTIFF created using gdal command with SPARSE_OK=YES.

Any hints appreciated.
Regards,
Fred.

I'm loading a Tif file created from SRTM DTED data and it works fine. My file is not as large as yours being only 30 arc-sec resolution. It's in BigTiff format.

Here's my gdalinfo output...

Driver: GTiff/GeoTIFF
Files: osgETerrainDT0.tif
Size is 17796, 20881
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 = (-180.025000000000006,84.004166666666677)
Pixel Size = (0.020231955406214,-0.008333333333332)
Metadata:
  AREA_OR_POINT=Area
Image Structure Metadata:
  INTERLEAVE=BAND
Corner Coordinates:
Upper Left  (-180.0250000,  84.0041667) (180d 1'30.00"W, 84d 0'15.00"N)
Lower Left  (-180.0250000, -90.0041667) (180d 1'30.00"W, 90d 0'15.00"S)
Upper Right ( 180.0228784,  84.0041667) (180d 1'22.36"E, 84d 0'15.00"N)
Lower Right ( 180.0228784, -90.0041667) (180d 1'22.36"E, 90d 0'15.00"S)
Center      (  -0.0010608,  -3.0000000) (  0d 0' 3.82"W,  3d 0' 0.00"S)
Band 1 Block=17796x1 Type=Int16, ColorInterp=Gray
  NoData Value=-32767

My config:
[osgEarth]  [Capabilities] Capabilities:
[osgEarth]  [Capabilities]   osgEarth Version:  3.0.0
[osgEarth]  [Capabilities]   OSG Version:       3.6.4
[osgEarth]  [Capabilities]   GDAL Version:      2.4.1
[osgEarth]  [Capabilities]   GPU Vendor:        NVIDIA Corporation
[osgEarth]  [Capabilities]   GPU Renderer:      GeForce GTX 1660 Ti/PCIe/SSE2
[osgEarth]  [Capabilities]   GL/Driver Version: 4.6.0 NVIDIA 457.30
[osgEarth]  [Capabilities]   GL Core Profile:   no

Your file is quite large so it might be taking a long time to cache the data (if you're using a cache folder which I highly recommend). For very large files, I've had better luck breaking it up into a mosaic of smaller Tif files.

HTH

Shayne