Hello to all! I have issue with inspire 2 results. When i create DEM and Orthomosaic of the Inspire 2 images using Agisoft photoscan or PIX4D mapper, at the same time i carryout DGPS survey to create DEM. there has been a lot of difference between the elevation values in both the results. the UAV based DEM has higher  values with respect to DGPS values.
I want to ask If there is any method to resolve this issue?

You would have to use Ground Control Points or re-geotag the pictures XYZ EXIF with positional information from an RTK receiver. If you don't use GCP or RTK then you are subject to a pixel error that relates to GPS accuracy. The relative information in each DEM (height of building/etc) is still accurate, just each pixel XYZ will have an error to its exact spot on earth.