[Geotiff] Vertical Units?

[Tillerson, Clint]

Hello All,

I'm updating an application to read/process elevation data in GeoTIFF
format.  I've come across a couple data sources that supply this type of
data in GeoTIFF format but omit specifying vertical unit of measure
within the GeoTIFF file (VerticalUnitsGeoKey, 4099).  It seem like a
reasonable expection that a GeoTIFF file that stores elevation data
would include this vital piece of information.  

I'm curious from you who are veterans when it comes to working with
GeoTIFF files, is this type of thing is common?

It seems the data are only as good as the supporting information that
identifies and describes it.  I've run into similar issues with other
types of data where a widely used distributor omitted the projection
parameters.  Are these common issues you typically have to deal with
when building custom applications that read/process GeoTIFF files?

Thanks for any insight!

Clint

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