Review on the different digital elevation model (DEM) vertical reference data types (relative accuracy).

One of the most significant technical specifications that the producer and user of a DEM (digital elevation model) must know is the vertical accuracy of the model. The model's accuracy dictates where it can be used. As a result, one of the most important steps in the evaluation of DEM is vertical accuracy analysis. The elevation data utilized in the evaluation must be compared to reference data that is three times more accurate than the model being evaluated, according to American Society for Photogrammetry and Remote Sensing ASPRS 2014 guidelines. In this work, 50 sources linked to evaluating the vertical correctness of DEMs (digital elevation models) for the time period between 2015 and 2021 were reviewed, categorized, and assessed based on reference data utilized to evaluate these models. Field surveys, LiDAR techniques, and topographic maps are the three types of reference data we use. According to the data, GNSS technology was used in 48% of the research, LiDAR techniques such as ALS (Airborne Laser Scanners) or Laser Ranging from NASA'sICES satellite were used in 33% of the research, and topographic maps were used in 15% of the research. [ABSTRACT FROM AUTHOR]