Field Plans with Phone GPS

Ok hear me out, we all know that mobile phone and commercial gps accuracy is completely unacceptable, but im looking for an app that you walk along the border of a field and plots that boundary. Recently Cadastre started operating in my Country and citizens are required to map out their properties. I got a friend that has inherited some piece of land in his village but does not have any plans made out. He only knows the vertices that surround the plot but in this point and time it would be mighty expensive to have plans made for each of the property he is required to declare. He will only do so if and when there is a sale associated