![]() ![]() It's not just the P1's higher-resolution which is driving the efficiency gains. This table shows that the P1 - with its three interchangeable lenses - can be flown at a higher altitude than the P4 RTK while obtaining the equivalent GSD. Having a higher-resolution camera also increases mapping efficiency, as it enables the drone to be flown higher - covering more ground in the process - while still capturing highly-detailed data.Īs a case in point, we'll explore this theory by once again using DJI's two photogrammetry solutions: the Phantom 4 RTK (below, left) and the M300 RTK and P1 camera. This level of detail is vastly important for projects requiring intricate details or measurements. and the resolution is so high that when you zoom in to that section, you can clearly count the number of holes in the bricks, or identify specific toys in the sandpit. The orange circle highlights a section of this orthomosaic which was captured from 50m altitude. And at 50m, it actually achieves a hugely impressive sub 1cm GSD.įor the record, the below images show how a sub-centimetre GSD can help to build highly-detailed and crystal-clear maps. This table shows how the flight altitude impacts the GSD, ie the lower the flight, the lower the GSD.Īs well as flight altitude, a higher resolution camera further improves the GSD.įor instance, look what happens when the P4 RTK - with its 20MP sensor - goes against the DJI M300 RTK and P1 camera, with its 45MP full-frame sensor:Īs you can see, the P1 achieves a lower GSD, thanks to its high-res camera. Two key factors impact your GSD: The quality of the camera - particularly focal length and camera resolution - and flight altitude.Īs a rule of thumb, the lower the altitude, the lower the GSD. To play it safe, land surveyors always use the lowest possible value when calculating GSD. Not only this, but knowing the size of each pixel is necessary to grasp the full scale of your map and make decisions based on clear information.Īn error of a centimetre or less may seem minor, but this mistake over hundreds of thousands of pixels, will create a serious mismatch between your map and reality, making measurements near impossible. Understanding GSD as a centimetre, inch or millimeter per pixel relationship makes it easier to calculate the size of the ground and features captured in your drone image. With this in mind, GSD is an important calculation for both aerial photography and photogrammetry, which is a commonly used technique for creating 3D topographic maps. This is because the bigger the value of the image GSD, the lower the spatial resolution of the image and the less visible the details. Take the below images as an example: The orthomosaic with a GSD of 5 cm (left) is far more detailed that the one on the right with a GSD of 30 cm. Therefore, the smaller the GSD, the higher the accuracy. So, if a drone achieves a GSD of 5 cm/px, that equates to one pixel on your digital map corresponding to 5 cm in reality. Or, to think of it another way, GSD can be considered as the length of one pixel in your map. GSD is defined as the length (in inches, centimetres, or millimetres) between the centres of two consecutive pixels on your map. What Is GSD And Why Does It Matter For Drone Surveys? This guide will teach you more about GSD, how to calculate it, and why flight altitude and a good quality camera matter. Without it, you risk collecting inaccurate data or having a map that isn’t useful. Put simply, your GSD impacts the accuracy of your surveys. If you are using drones for surveying, then understanding GSD (Ground Sample Distance) is crucial. Sample datasets from the DJI M300 RTK-P1.How to calculate GSD, using online or manual methods.Factors that impact GSD, such as flight altitude and your camera specifications. ![]() A guide to GSD (Ground Sample Distance) for drone surveying: What it is and why it is important. ![]()
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