Markers
HemoVision uses photogrammetry to reconstruct parts of a scene in three dimensions. Traditional photogrammetry, however, can struggle in low-texture environments such as painted walls, and often requires a large number of photographs to produce reliable results.
To address these limitations, HemoVision incorporates fiducial markers into the documentation process. These markers are placed at the scene and can be accurately detected by the software. Once detected, they allow HemoVision to automatically correct perspective distortions, determine the position of photographs in 3D space, and reconstruct scenes to scale, even when working in low-texture environments or with a relatively small number of photographs.
Marker Types
HemoVision uses two types of markers, which are illustrated in the figure below. Each type is discussed in more detail below.
Detail Markers
Detail markers are smaller markers placed in the vicinity of stains and bloodstain patterns that you intend to analyze.
Each detail marker:
- Has a unique numeric ID
- Serves as a local geometric reference
- Allows accurate positioning of detail images in 3D space
Detail markers are placed in areas that contain stains or patterns that you wish to include in the reconstruction and later analysis.
Overview Marker
The overview marker is larger and is used to position the overall reconstruction in 3D space.
It contains a reference cross in the top-left corner. By default, this reference cross will be positioned at the origin of the world’s coordinate system, with the marker's long side aligned with the X-axis, and the marker's short side aligned with the Y-axis (see the above image for reference, assuming a Y-up coordinate system).
Info
More info on marker placement and reconstruction positioning is presented in the following subsection "Marker Placement".
Why Markers Matter
Markers allow HemoVision to:
- Reliably and accurately reconstruct the geometry of the scene, even when working in low-texture environments or with a relatively small number of photographs.
- Remove perspective corrections so that photographs can be taken freely
- Automatically position detail images in 3D space
- Scale the reconstruction and images to real-world units
Tip
Each reconstruction contains exactly one overview marker, and an arbitrary number of detail markers.
You cannot place too many detail markers, but you can place too few.
Found a mistake?
Did you find a mistake, or does a page contain outdated information or something that is not working correctly? Please let us know so we can review it and fix it as soon as possible.
Forentrics - Bringing Evidence into Focus