pkpolygonize: 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/pkpolygonize - from package: pktools

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

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