xgpsspeed: 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 Debian possible default full paths are:

/usr/bin/xgpsspeed - from package: gpsd-clients

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

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