grdcontour: 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/grdcontour - from package: GMT

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

On Debian possible default full paths are:

/usr/lib/gmt/bin/grdcontour - from package: GMT

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

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