geographiclib-get-gravity: 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/sbin/geographiclib-get-gravity - from package: GeographicLib

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

On Debian possible default full paths are:

/usr/sbin/geographiclib-get-gravity - from package: geographiclib-tools

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

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