Key factors defining the quality of the 3D model
For the qualitative 3D object reconstruction, you have to pass 3 main steps:
- Data gathering (photo shooting);
- Data processing;
There is a widespread opinion, that flying from the lower height (lower than 30m), the best GSD result is possible. This is not always true, because some things depend on the flying and photographed area, the UAV/drone built-in cameras, etc.
For instance, for the DJI drones (phantom or inspired), most commonly used cameras are 12 MP, but you should pay attention to some of the details – in which height photos are being made, what is the speed, time and weather conditions. Recommendation is that with such cameras it is best to fly 40m-80m ranges. By flying above, there is a high risk of reducing GSD accuracy. Such cameras are not suitable for flying at an altitude lower than 30m, due to insufficient lighting (the shutter speed is longer, blurring effects are often exchanged).
Using the 20 MP lenses, the height may be higher, but you should not exceed the legal permitted height of 120 m. These cameras have a better lighting, so the reaction of the quickly changing objects is not that sensitive. Nevertheless, even for such cameras, it is sometimes necessary to use filters to reduce the lighting and probability of the shadows.
Advantages of flying above
The benefits of flying above are the following:
- Taking the necessary photoset from large areas can be quicker;
- No need to interrupt the drone track (as the average drone flight mode battery duration is 20min, it enables to fly large spaces without necessity to land and switch the battery), thus increasing the accuracy.
In lower areas, there is also a possibility to use 20MP cameras – their lighting is higher and the maintenance is simpler.
It is important to pay attention to weather conditions. If the weather is gloomy – the lighting weakens, maintenance conditions increases. Although, it is best to take photos when the objects are not throwing the shadow, a gloomy day is not always the best decision, because the lower precision of the camera is more likely to get the blurred effect.
The best time for photos is around the midday, when the sun is at its peak and objects have the smallest possible shadow. The alternative to decrease the shadow possibility appearance in the pics, is to fly a drone in a gloomy day, but then we have to consider the lenses and the level of gloominess. It is because at the lower lighting the shutter speed is decreased, which results in a blurr effect when moving the camera. That’s why the 20MP cameras are the best to shoot in such weather conditions.
On a sunny day, the polarizing glass to the lens can be applied, thus increasing the accuracy of the object. It succeeds only on the high quality lenses, such as 20 MP. Polarizing filters reduce the amount of light entering the lens. It should be noted, that polarizing filter also works as the N2 (we will explain more about it in the next article).
As we are specializing on the object reconstruction for the mining industry, which is usually large in size and need a clear and realistic object reconstruction, it is enough to have a most commonly used at least 12 MP camera, use 90 degree camera angulation and single grid track. In this way, you save time and do not harm the quality of the object reconstruction in a 3D mode.
As the strength of Pixprocessing_Mining software is an analytical part, we share our insight to ensure maximum use of the software. Evaluate some of the main criteria for taking pictures, because the better input – the preferably output will be.