Elevated Target Markers &
Spinner Target Markers

Elevated Target Markers (ETMs) and Spinner Target Markers (STMs) provide a means to connect independent photogrammetric networks that would otherwise not share common points. ETMs and STMs are imaged in more than one network, thus allowing multiple photogrammetry surveys to be linked into a uniform coordinate system.

An example of where ETMs and STMs are useful is shown below. The task in this case was to tie together three iWitness surveys of a semi tanker explosion, one on the freeway overpass and two others on the roadway below the overpass.

Application in the field

By linking the networks above and below an overpass, police utilized iWitness to map a tanker explosion in a crash scene that was 1000 feet in overall length. The police investigator's on-scene time for this incident mapping, using two digital cameras, was only 70 minutes.

Tanker explosion mapped with iWitness

Motorist uses a cell phone to image a semi tanker explosion

Photogrammetry ETM/STM targets on overpass

Click here for an expanded view of ETM\STM use on the overpass
iWitness polylines, natural marked features and photogrammetric markers

iWitness photogrammetry imaging angles

Trooper reviews imaging angles from multiple view perspectives

Troopers imaging crash for iWitness 3D measurement

Trooper mapping the incident below the overpass while working around
Hazmat and Fire Department vehicles

Plan View of the trooper's iWitness mapping, the two freeways,
overturned tanker, semi cab, car, railroad and roadway crash evidence

ETMs and STMs are applicable in many applications where intervisibility between surveys to be connected is otherwise difficult or impractical, a condition which can occur, for example, with crashes involving vehicles running over steep embankments.

Solutions for Complex Camera Geometry in Accident Reconstruction
In order to measure multiple photogrammetric networks and "link" them into the same common coordinate system, at least 4 "Tie Points" (TPs) are required. TP's measured in iWitness may be natural feature (discrete object) points or special targets, such as ETMs or STMs. It is important that TPs are well separated and distributed in two dimensions (ie they cannot be approximately collinear) to facilitate a geometrically strong join, which in turn is carried out via the iWitness Project Linking tool.

ETMs & STMs designed for work with iWitness
are offered as accessories for iWitness. These stand approximately 8’ (2.4m) off the ground when mounted to a standard tripod extended to a height of 58". The ETM's 3/8" diameter fiberglass rod is secured to a standard 1/4"-20 tripod stud. A special adjustment nut permits the assembly to be rotated about the vertical axis, so the target can be spun to face any horizontal direction at the base location of the ETM-to-tripod mount. The ETM target itself can then be imaged with a digital camera over 360 degrees, making it ideal for linking iWitness photogrammetry networks. The ETM is also removable from the rod for easy storage.

STMs also allow the photogrammetric target to be spun on its axis, horizontally through 360 degrees. The STM is weighted with anti-slip grip tape installed to the base. STMs break down for easy storage and deployment. A galvanized plate is velcro hook and loop secured to the base.

The target components for both ETMs and STMs are removable for easy storage. When combining both ETMs & STMs, the user can easily achieve the required 2D separation of the target points that is necessary for a strong join within the unified 3D object coordinate system.


A quantity of two ETMs and three STM's are sold and ship as a set. The Manfrotto tripods displayed are for illustrative purposes. Any consumer grade tripod will work with ETMs.

STMs can optionally be purchased in sets of quantity 20, by special order request. Contact sales@iwitnessphoto.com for STM special order information.

Purchasing (domestic):
- shipped anywhere within the USA for $149.00 and shipping.

To order within the USA, use the On line method

Purchasing (international):

- shipped most places internationally for $149.00us, and shipping.

Contact sales@iwitnessphoto.com for more information on your international order.

Shipments are typically made within 48 hours of receipt of the order.

Delivery Time:
Shipments arrive to their destination within 4 days (domestic) and 10 days (international) of shipping. The customer is emailed the tracking number for the shipment.

The delivery consists of one box.

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