pcl_pcd_convert_NaN_nan: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/pcl_pcd_convert_NaN_nan - from package: pcl-tools

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/pcl_pcd_convert_NaN_nan - from package: pcl-tools

You may install the required package with command apt-get install {package}

Error in other languages:
pcl_pcd_convert_NaN_nan: bevel nie gevind nie
pcl_pcd_convert_NaN_nan: comandă negăsită
pcl_pcd_convert_NaN_nan: comando não encontrado
pcl_pcd_convert_NaN_nan: commande introuvable
pcl_pcd_convert_NaN_nan: command not found
pcl_pcd_convert_NaN_nan: käsku ei ole
pcl_pcd_convert_NaN_nan: không tìm thấy lệnh
pcl_pcd_convert_NaN_nan: komanda nerasta
pcl_pcd_convert_NaN_nan: Kommando nicht gefunden.
pcl_pcd_convert_NaN_nan: kommandot finns inte
pcl_pcd_convert_NaN_nan: komut yok
pcl_pcd_convert_NaN_nan: nie znaleziono polecenia
pcl_pcd_convert_NaN_nan: níor aimsíodh an t-ordú
pcl_pcd_convert_NaN_nan: no se encontró la orden
pcl_pcd_convert_NaN_nan: no s'ha trobat l'ordre
pcl_pcd_convert_NaN_nan: opdracht niet gevonden
pcl_pcd_convert_NaN_nan: parancs nem található
pcl_pcd_convert_NaN_nan: perintah tidak ditemukan
pcl_pcd_convert_NaN_nan: príkaz nenájdený
pcl_pcd_convert_NaN_nan: příkaz nenalezen
pcl_pcd_convert_NaN_nan: команда не найдена
pcl_pcd_convert_NaN_nan: командата не е открита
pcl_pcd_convert_NaN_nan: 命令找不到
pcl_pcd_convert_NaN_nan: コマンドが見つかりません