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Hello everyone. I recently acquired the Phantom 4rtk drone with its respective D-rtk-2. Many times for my work I need to solve topographical problems and I acquired this drone with the intention of not relying on control points. I don't need pinpoint accuracy and from what I read this computer provides it to me. I made my first drone flight in an area with a topography that varies from 7 meters above sea level to 44, according to the topography I was given when I arrived at the project. The flight was in the 2D mode of dji fly, connecting the Rtk with a connection to 21 satellites. The altitude was 100 meters as it had to cover an area of 7 hectares. The flight was performed in normal weather conditions except for a thin layer of very high clouds. Now I explain what I did before I flew: 1. My first problem was when installing the RTK station. When I activated it and it showed its location, the x and y coordinates appeared that I assume were fine. After that enter these coordinates in the setting of the D-DRtk-2 as the tutorial says. The problem was when I wanted to put the altitude of the equipment in which I was marked that we were 60 meters above sea level. Almost 18 meters more than the surveyors had measured for the same place. 2. I enter the doubt and change my position to another place with a lower level exactly 20 meters above sea level and the device frame me 30 meters. 3. After this I told myself that these errors will most likely be corrected in the post-process. Enter the values as the tutorial says. 4. Having purchased the photos, I go on to process it first in dji terra as I am occupying the free month they give. Perform a 2D orthophotomosaic. the results in x and y were impressive and be very satisfied. 5. When I saw the DSM that generated this flight, my doubts began. Some places had 20 meters of altitude where the actual measure is 7 or 10. 6. Make 3 more flights, one 3D in the same DJI application, another 2d but with a different grid, do not activate the image correction in the application as I read it was recommended, take oblique photos at the end of the flight. etc. 7. The 3D model threw the same error at the z-axis in both dji terra and Agisoft photoscan. 8. In some forums I read that the camera had to be calibrated, but as I am a novice in this I did not understand how it was done. 9. I am really frustrated as this is not a low cost equipment and I thought it would help me in my work. 10. Although when checking the plan of the project in 2D fits perfectly and there are minimal variations, no more than 2 CM on the z-axis I have almost 20 meters of error! I would like you to help me solve this problem. I would be very grateful.
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