Everything you need to know about photogrammetry

Everything you need to know about photogrammetry

There are many photogrammetry based software that you can use to process captured images. It is worth noting that while the rules of capturing your photos are universal to all software, due to how each software process the data differently, there are some software-specific guidelines that will enable you take advantage of the full power of certain a solution.

The Software

There are many photogrammetry based software that you can use to process captured images. It is worth noting that while the rules of capturing your photos are universal to all software, due to how each software process the data differently, there are some software-specific guidelines that will enable you take advantage of the full power of certain a solution.

For example, for our “Pixprocessing” software application, that facilitates customers daily work by performing 3D object reconstruction from aerial and handheld imagery, it is easy to precise object measurements and volume calculations, “Pixprocessing” is also capable to quickly process thousands of photos, locally performs processing, simple integrates with modern tools and existing GIS and CAD software.

PC

Here are some basic requirements for your PC:

minimum hardware and software requirements
Recommended hardware and software requirements

Equipment

There are also some devices that you need:

Camera: The ideal camera would be the one that offers the sharpest image, pixel count is important but not that much, and you can still do some incredible scans with the cheaper one, just have to take more pictures. In fact, more people are starting to do some decent scans using their phone’s camera.

Lens: Use a fixed focal length lens, the sharper the better. If the camera came with a variable lens and you want to use that, as long as you use the upper-limit or the lower-limit and you stick with it during the entire capture session, you should be fine.

Camera remote: It is useful, especially when your own shadow is appearing in the scan and you have to take the picture from a distance, or if your camera is out of reach like when it’s attached to pole to get higher angles.

SD Card: If you plan to take a lot RAW photos, then a good SD card with a large capacity would be a good investment.

Monopod: It’s useful, especially if you have shaky hands and you can’t use a higher shutter speed.

Tripod: You need one, especially when you are in some low light situations, and you can’t use a flash, or you have to take long exposure images.

Color Checker: This can be useful if you want to scan some accurate colors.

Drone: This is mostly useful if you are trying to scan a terrain. Other use of a drone would be to scan a building or big structures, especially to take photos from location that are out of reach. You can always combine your aerial data set with your ground data that you took using your DSLR. In fact, it is recommended since there is a limit to the type of camera you can attach to an affordable drone, and there for a combination of the two will boost the quality of your scan.

CPL: Cross Polarized Photography is a useful technique that consists of attaching a polarized filter to you light source, and your camera lens in order to light your model without creating highlights, which will help you create more consistent and flat textures.

Special De-Light Rig: This special rig is usually used for de-lighting, which is removing the lighting information that belongs to the original environment in which the scanned object used to be. This will enable us to re-apply a different lighting information that matches the new environment the scan will be placed in.

Scale bar or Coded Targets: Coded targets are printed markers that can be placed in the scene before photos are taken. It is best to use when you have a small object that you would like to scan, and that needs to have an accurate scaling.

Ground Control Points: This represent an actual 3D point in your scene that belongs to your scan, and that you highlight on multiple images in order to manually align some photos that the software failed to align usually for the lack of overlap between, picture.

Spray: Photogrammetry does not scan translucent and reflective surfaces well, and a way to overcome that would be to cover your object using a harmless matt spray.

Turntable: It helps to rotate the object while the camera stays fixed.

Useful tips

Here are some useful tips for a better result in photogrammetry:

  • Do not limit the number of images, use the highest resolution that is possible.
  • Each point in the scene surface should be clearly visible in at least two high quality images.-
  • Always move when taking photos. Standing at one point produces just a panorama and it does not contribute to a 3D model creation in fact it will introduce some errors to your scan. Move around the object in a circular way while trying to assure 80% overlap between photos.
  • Complete loops. For objects like statues, buildings and other you should always move around and end up in the place where you started.
  • Rotate the camera (horizontal and vertical ensure better calibration).

Lastly, don’t forget to experiment, feel free to break some rules if you think it fits, improvise. And remember, that Pixpro team with its “Pixprocessing” software  is always ready to help you. Good luck!