i’ve to generate a DEM in a area of 20 Km², I’ll flight at 120 m (400 feet), resolution its about I would download at 1 meter, so what overlap shoul I use? How much can I decrease?
What kind of relative accuracy are you looking for? I am not clear if you are looking for 1 meter RMSE or GSD?
Or are you looking for absolute accuracy and are using GCP’s?
GSD its about 5 cm, but I do not need that accuracy or even GCP’s, Just wanna optimize my flight, I’d like to known how much can a i decrease overlap to save time
This all will be plenty achievable. At 400ft you should be able to get about the 4-5cm GSD you are looking for and I would expect about a 15-20 cm relative accuracy. You image RMSE’s should be about 3-5 meters, but that is just a number in my opinion. It can be an indicator of bad data though if it gets much above that.
I would recommend starting at a 75/65 overlap. Anything above 80 frontlap is wasted time and anything below 70 starts to diminish your images per point which limits how well the image locations are corrected. It is not too bad to go down to 70/60, but I would only do that if it makes a significant difference in the flight efficiency. Most of the time you can tweak the flight direction and the overlaps by 2-3% to improve the efficiency of the flight quite a bit.
How do you think you will go about collecting this large of an area and deriving your flight plans?
75/65 it wil take 615 minutes to flighr, while 70/60 464 minutes
Guess I’ll try 70/60 at 400 feet, should be ok at this height in my opinion, if does not look that good I’ll set 75/65, thanks
For that amount of area I think you are right, but the overlaps won’t make a difference on how it “looks”. They may affect the accuracy and measurements of distances greater than 500ft and vertical will be approximately 1.25-1.5x the error of the horizontal.