The Comparison of Different Procedures for the Preparing of the Digital Elevation Model, Case Study: Noferest watershed, Birjand township, South Khorasan Province

The exact estimation of qualitative and quantitative characteristics of the natural phenomena requires a great deal of time and expense. Therefore، the interpolation procedures are used as a suitable solution in the estimation of the places which are uninformed to other researchers، and haven''t been sampled yet. The reason for the choice of the mentioned procedures is that there are many maps derived from the Digital Elevation Model، and these maps have application in different analyses، and also they may have influence on the result of an analytic research، using different scales. If the main source which is Digital Elevation Model malfunctions، the whole project will have more errors. The main subject of this research is the choice of the most suitable procedure for the formation of the Digital Elevation Model which can present more real-life model from the natural condition of the earth، with high precision. The research purpose is the comparison of some of the procedures for the preparing of the Digital Elevation Model، including TIN (Triangulated Irregular Network)، TOPOGRID، and also Digital Elevation Model derived from 3-dimensional satellite images. The mentioned procedures were performed on the data of theNoferest watershed in 40 kilometers of the east of Birjand city and their results have been compared precisely with each other and also with the data derived from the 2-frequency global location finder systems (DGPS). The results obtained from the comparison of the amounts of minimum and maximum differences and also the comparison of the RMSE amounts between the Digital Elevation Model and the DGPS data in 10 research zones، show that TIN procedure which has obtained the maximum amount of difference، 5 times with no minimum amount، has more errors، and the Digital Elevation Model of SRTM which has obtained the minimum amount of difference، 3 times with no maximum amount، has higher precision. In this procedure، the TOPOGRID and TOPOGRID INFORCE and also the Digital Model derived from the ASTER images، are placed in the subsequent ranks.