31
General / Re: Urgent help needed - Ridge lines in DSM/DEM export
« on: February 22, 2018, 08:27:06 AM »Hi again Pkroks,
You could try to run photo alignment on ALL images (choose quality setting MEDIUM unless you have a high-end computer) to see if the ridge problem persists (also use your GCPs). For the dense point cloud you would then divide your project into several chunks (using a Python script) and then merge all chunks at the end for the final product (unless you have a high-end computer/multi-GPU setup that can compute a dense point cloud from over 4,500 images).
In some areas where aerial surveys overlap (as seen in your processing report) you could even disable a few images to speed up processing.
Regarding settings for your camera. Many people use manual focus set to infinity (when flying high above the ground) because autofocus might a) be too slow which means the picture is not taken where it should be taken and b) might simply get it wrong (leading to out-of-focus/blurry images).
Use ISO 100 or 200 (if necessary even 400), shutter priority or manual and set your aperture to f/6.3 or f/7.1 (which is generally OK because you don't want to 'suffer' shutter speed-wise; remember the exposure triangle). These are the settings I commonly use on my Sony Nex 7 and A6000 (attached to a multi-rotor though).
If you shoot fully manual, adjust your aperture/shutter speed/ISO by using the live histogram on your camera. When working outdoors it is hard to tell on the tiny screen of your camera if the picture is properly exposed or not, but it is easy to see in the live histogram.
Last but not least, DON'T use the automatic white balance, but manually set it to cloudy or sunny (depending on the weather/light conditions).
All the best.
Regards,
SAV
Hi Sav,
Please can you share or help with the python script to split and then merge after the dense cloud processing. The system is as follows:
Intel i7 8700k 3.7ghz
32gb ddr4 ram 2400mhz
nVidia GTX1070 8gb
samsung 850 evo 250gb ssd
1tb seagate sshd harddrive.