Support of DTED and SRTM

Hello

Are DTED format or SRTM Supported?

With a DTED I run the following command `rio rgbify -b 10000 -i 0.1 N43.dt0 n43.rgb.tif` and I get the following message : `rasterio._err.CPLE_NotSupportedError: DTED driver only uses the first band of the dataset`

With a SRTM downloaded from [http://dwtkns.com/srtm/](url) i run the same command `rio rgbify -b 10000 -i 0.1 srtm_38_04.tif srtm_38_04_rgb.tif` and I get this message `Given nodata value, -32768.0, is beyond the valid range of its data type, .`

I may be doing something wrong somewhere but so far i've not seen where...
Regards

Start by reproducing the reported `rio rgbify` commands with the DTED and SRTM inputs named in the issue, then inspect the resulting driver and nodata errors. Check how the tool handles single-band DTED data and SRTM nodata values; done should establish whether these formats are supported and provide working behavior or a clearly documented limitation.

Written by the indexing model from the issue text.