[OSSIM] OSSIM Elevation

[Mike T. <mik...@gm...>]

I recently built and installed OSSIM but am having trouble using elevation
data.
OS: Ubuntu 22.04.1 LTS
ossim-info --version
1.9.0

Snip from my ossim_preferences.txt file:
elevation_manager.elevation_source0.connection_string:
$(OSSIM_DATA)/elevation/srtm/1arc_tif_from_USGS
//elevation_manager.elevation_source0.connection_string:
/home/mike/elevation/srtm/1arc_dt2_from_USGS
//elevation_manager.elevation_source0.connection_string:
/home/mike/elevation/srtm/1arc_ras_from_tif
//elevation_manager.elevation_source0.connection_string:
/home/mike/elevation/srtm/1arc_bil_from_USGS
//elevation_manager.elevation_source0.filename:
/home/mike/elevation/srtm/1arc_bil_from_USGS
elevation_manager.elevation_source0.enabled: true
elevation_manager.elevation_source0.type: srtm_directory
elevation_manager.elevation_source0.min_open_cells: 25
elevation_manager.elevation_source0.max_open_cells: 50
elevation_manager.elevation_source0.memory_map_cells: false
elevation_manager.elevation_source0.geoid.type: geoid1996

(the lines which are commented out are other things I have tried)

I downloaded 1 arc second SRTM data from USGS, I tried all available
formats: .bil, .tif, and .dt2.  I also tried converting the .tif to a .ras.
Specifically, I downloaded n39_w106_1arc_v2.*

ossim-info --check-config reports:
elevation sources loaded:
elevation_source[0].connetion_string:
/home/mike/elevation/srtm/1arc_tif_from_USGS

This is encouraging, but
$ ossim-info --height 39.5 -105.5
reports:
elevation.info.cell:  not_found

I loaded the data from USGS into QGIS to confirm my assumption that 39.5
-105.5 is within the specified file.

I have also tried renaming the SRTM files from the USGS to:
n39w106.*
which I understand is the convention for SRTM.

Any help would be appreciated.

Thanks,

Mike