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How to measure a stair case

Preparation

For stairs measurement please download the special targets and two start boards using the links in the Settings view of the app (one level back). Print the sheets and the targets on cardboard or glue them onto cardboard such that the targets are flat and not moving.

Positioning of the measuring markers

  • Place two markers on each step. The green tip of the marker defines the point to be measured.
  • Place one start board at the bottom platform of the stairs.
  • Place additional targets around the bottom start board.
  • Place the other start board at the top platform of the stairs.
  • Place additional targets around the top start board

General considerations

The photos must meet the following requirements:
  • The pictures must be sufficiently bright. Turn on all available light sources. The flash of your device's camera is turned on by default. If it isn't, turn it on.
  • Set your device's camera to wide angle/minimum zoom. Do not change the zoom setting while taking photos
  • The images must be perfectly sharp! (see images below)
  • Make sure that at least six targets are visible on each photo. Make sure that the left and the right target of a step are visible in the image
  • Do not move or touch the markers or the start board any more. Even small shifts could distort the measurement result. Start over with the photos if need be.
  • Stand next to the wall or the handrail when taking photos (also on platforms). Standing in the middle of a step or a platform may reduce precision and recognition rates.
  • Always take a step after each photo. Experience has shown that projects have a significantly higher failure rate, when multiple photos are taken without taking a step in between. Typically perspectives or steps are frequently skipped when taking multiple photos on the same step.
  • Do not take multiple photos from the same spot without moving you position. Almost identical photos are not helpful and can cause serious issues.
  • Use a focal length (converted to full frame dimensions) between 24mm and 35mm. If the focal length is longer the field of view is too limited. If it is shorter image distortion becomes a problem.

Taking photos

  • Start at the bottom platform.
  • Take seven photos of the starting sheet.
  • Walk up the stairs and take a photo on each step.
  • Take at least seven photos on the top platform, especially from the edges of the platform towards the targets.
  • Walk down the stairs and take a photo on each step in portrait mode. Try to cover as many steps as possible with one photo.
  • Take seven photos of the starting sheet.
  • Walk up the stairs and take a photo on each step.
  • Take at least seven photos on the top platform
  • Walk down the stairs and take a photo on each step.
  • Divide the stair platforms into imaginary 50cm x 50cm squares and take photos out of each square.

Evaluation

Click "Compute" in the 3D view. A few seconds later you should see the results. You can export them from the settings menu at the bottom right.

Right and Wrong

Do not step on the markers
Do not step on the markers 		Markers are touched when taking pictures
Wrong: Don't touch or move markers while taking pictures
Markers clearly visible
The markers should be clearly visible and, e.g., not be covered by other steps 		Markers not visible on the right side
Wrong: markers not visible on the right side
At least six markers per picture
At least six markers per picture and two per step 		Only one side of a step is visible
Wrong: Only one side of a step is visible
Sharp pictures are necessary
Sharp pictures are absolutely necessary 		Picture not sharp
Wrong: blurred picture
4 markers should be used for wide steps
For steps wider than 30cm, 4 markers should be used per step 		Too long distances between the markers
Wrong: Too long distances between the markers
You should go upstairs and downstairs wide-ranging
You should go upstairs and downstairs on the very left and the very right side of the stairs. so that pictures are taken from as different angles as possible. A dot means that you should take pictures at this position. 		Photos are all taken in the middle of the stairs
Wrong: Pictures are all taken in the middle of the stairs

Disclaimer

The accuracy is influenced by the condition of your device's camera, the condition of the targets and the way the photos are taken. All these factors cannot be controlled by Linearis3D. Linearis3D does not accept any responsibility for the accuracy or feasibility of a measurement. The user must take appropriate measures to make sure that the results meet the user's requirements. Always check your measurment with an independent secondary measurement device, e.g. a laser distance measurement tool.