Trimble V10 Tech Tips Part 1/2

Trimble V10 Imaging Rover: Shock-Absorbing Tip

Products

• Trimble® V10 Imaging Rover

Question

In what way is the tip of the Trimble V10 Imaging Rover different to normal rods?

Answer

The Trimble V10 Imaging Rover has a shock-absorbing tip.

Large and abrupt accelerations are introduced into the rover when the rod is set onto the ground. This can happen in the field even with carefully handling. If the rover is set from a height of 5 cm, an acceleration of 15 g impacts the rover. From a height of 30 cm height this will be 100 g. The datasheet reports that 100,000 drops from 5 cm and 100 drops from 30 cm will not influence the calibration status of the rover. Due to an appropriate damping, the shock absorbing tip makes sure that shocks and jerks are absorbed or at least four times reduced. This is softer not only for the system, but also much more comfortable for the operator.

Trimble V10 Imaging Rover: Sensors in Camera Head

Products

• Trimble® V10 Imaging Rover

Question

Which types of sensors are included in the Trimble V10 camera head?

Answer

A series of sensors is included in the camera head to work cooperatively with the cameras:

• A 3-axis accelerometer measures the absolute orientation of the camera head. It delivers any angle to gravity between 0° and 180° with an accuracy of 1°. It works in a range of ± 8 g.
• 2-axis tilt sensors measure the tilt of the rod in 2 components in a range of between 0° and 15° with a higher accuracy of 0.03° (33 mgon). The offset accuracy at the camera head in 2 m height is 1 mm.
• A 3-axis magnetometer measures the orientation of the camera head (azimuth) and the orientation of the tilt values. The accuracy is 1° at undisturbed surrounding.
• Magnetic azimuth and tilts deliver approximate rotation parameters for the external orientation of the panorama.
• Gyros for 3 axis measure possible rotations of the rover during the exposure of the panorama images. A message appears if this happens. For this reason, using a bipod is always recommended when capturing panoramas.
• The sensors are calibrated with respect to the coordinate system of the camera head.

Trimble V10 Imaging Rover: Sensor Calibration in the Camera Head

Products

• Trimble® V10 Imaging Rover

Summary

This document describes how the sensors in the V10 Imaging Rover camera are calibrated.

Technique

Parameters that are calculated in the calibration process for the sensors are:

• Scale factors
• Deviations from rectangularity
• Offsets
• Position and orientation relative to the center of the camera head

Sensors are calibrated using a precise cube mounted on a turntable that can be tilted. The sensor board to be calibrated is placed on the top of the cube while a reference board is mounted inside. The cube will be placed in 3 orientations and tilted in several angles.

Note: The collimator to the left can be used to check and adjust the tilting plane by exchanging the corner cube with a total station.

Trimble V10 Imaging Rover: Camera Head Calibration

Products

• Trimble® V10 Imaging Rover

Summary

This document describes how the cameras on the V10 Imaging Rover are calibrated.

Technique

The camera head of the V10 Imaging Rover is calibrated during production – it is placed on a turning table in the center of the calibration chamber:

On the walls and on the ground floor around the V10 Imaging Rover large tables are mounted at different distances. Many targets are arranged on the tables in a checkerboard pattern:

The geodetic coordinates of the target centers are measured with a total station in higher-ranking accuracy. The coordinate system is related to the center of the camera head.

During the calibration process, 38 panoramas are captured, each after turning the head 360°/38. The image coordinates of the target centers are measured automatically in all panoramas:

In total there are 1040 targets. Measurements to the targets are done in 38 orientations so that 280 images in all are used. The total number of more than 30000 measurements is reduced to 4200 to generate an equally distributed target field.

In a weighted bundle adjustment process, all parameters of the calibration are calculated for each of the 12 cameras, as follows:

For the interior calibration:

• Principle point
• Camera constant
• Parameters of the
  • Radial symmetric distortion up to the 7th order
  • Non-symmetric distortion; magnitude and direction

For the exterior orientation (relation to the center of the camera head):

• 3 shift parameters
• 3 rotational parameters

The maximum residual of all residuals in the adjustment is less than 1 pixel. The standard deviation of unit weight is < 0.3 pixel.

The following image shows an example of the residuals at different positions of the camera chip. The maximum residual here is 0.31 pixel. The length of a 1 pixel residual is given to compare it with the residuals in the image:

Related information

Graesser, Christian; Koehler, Martin: Multi-Kamera Rover Trimble V10. Beschreibung des photogrammetrischen Messsystems, der Kameras und der Sensoren sowie eine Genauigkeitsanalyse. Presentation at the “Oldenburger 3D Tage”, Oldenburg Germany, 12 February 2014

Trimble V10 Imaging Rover: System Overview

Products

• Trimble® V10 Imaging Rover
• Trimble R10 GNSS receiver
• Trimble Tablet
• Trimble Access™ software
• Trimble Business Center software

Question

What are the components that make up the Trimble V10 Imaging Rover system?

Answer

The image shows the Trimble V10 Imaging Rover with the camera on top of the power rover:

To measure the positions, you can set an R10 GNSS receiver on top of the camera. Alternatively, if the V10 Imaging Rover should be positioned by a total station, you can replace this with a 360° prism.

To control the system in the field, you will use the rugged Trimble Tablet field computer running the Trimble Access field software.

The V10 Imaging Rover is powered by two batteries. This should provide sufficient power for one measuring day. The battery compartment at the lower end of the rover ensures that the total weight is better distributed along the rod. It is easier to carry, and the balance is much better when the rover is not set on the tip.

Post-processing of field measurements – geodetic measurements, photogrammetric measurements, and bundle adjustment – is carried out in the Trimble Business Center software.

Trimble V10 Imaging Rover: Coordinate Systems

Products

• Trimble® V10 Imaging Rover

Question

What are the coordinate systems for the different parts of the Trimble V10 Imaging Rover?

Answer

The following figure below shows the different coordinate systems in the V10 system in a simplified form. All the systems are connected to each other by calibration parameters – 3 shift and 3 rotational parameters:

• The image coordinate system is related to the camera coordinate system.
• The camera coordinate system is referenced to the system of the camera head.
• The sensor systems on the sensor board are calibrated to the center of the camera head.
• The camera head is set centrically on top of the rover.
• The position sensor is adapted on top of the camera head.
• The camera head and position sensor are referenced by exact mechanical adaption.
• With the measured position, the height at the rod, the rod tilts and the orientation by the measured azimuth the rover is referenced to the user coordinate system.

Trimble V10 Imaging Rover: Weights

Products

• Trimble® V10 Imaging Rover
• Trimble R10 GNSS receiver
• Trimble Tablet

Question

What are the weights of the different units I may need for a project using the Trimble V10 Imaging Rover?

Answer

The following table shows the weights of the units related to the Trimble V10 Imaging Rover:

From this table, we can now calculate the total system weight for different configurations:

If you use the V10 Imaging Rover as a stand-alone instrument, the resulting weight is 5.7 kg. If you add the R10 GNSS receiver, the weight increases to 6.8 kg.

If this is too much to carry for a whole day, you can divide the job into two parts:

• The first part will be where GNSS measurements are collected and the V10 Imaging Rover is not used. This will be the largest part of the job. You will not need the bipod, and the weight decreases to 5.2 kg. Alternatively, you can use the normal R10 GNSS rod, with a weight of 3.6 kg only.
• The second part of the job is collecting points where panoramas are useful, and for this you need the V10 Imaging Rover and the bipod. This makes up a smaller part of the job and can be done at the beginning or at the end of the field work or whenever the environmental conditions are the best for the panoramas.

Trimble V10 Imaging Rover: Preliminary Project Planning

Products

• Trimble® V10 Imaging Rover

Question

Can I do preliminary planning for a project using the Trimble V10 Imaging Rover?

Answer

The configuration for close-range photogrammetric stations is usually planned very carefully before starting the measurements in order to achieve the required object accuracy.

If you perform surveying measurements using GNSS receivers or total stations, little the planning is required before going to the site.

• With GNSS measurements, the shadowing of satellites or multipath effects must be taken into account.
• With total stations, the optimum positions for the stations can easily be decided at the site. You only need to provide coordinates for stationing and site calibration routines before you go to to the site.

With the applications the V10 Imaging Rover is used for, it is doubtful whether the photogrammetric part can or will be planned in the same way that photogrammetrists would have done previously. In fact, you may assume that the configuration of panorama stations will be done on the fly during the job.

For example, if you use Google Earth for preliminary planning, the image would be similar to that shown below:

However, in the field you should ensure that objects such as walls, trees, or coppices do not hide your objects of interest. This is why planning done using a view from the top may not really help.

Trimble V10 Imaging Rover: Field of View

Products

• Trimble® V10 Imaging Rover
• Trimble Access™ software

Question

What is the field of view with the Trimble V10 Imaging Rover?

Answer

The camera system consists of 12 cameras, 7 panorama cameras and 5 down-looking cameras.

The panorama cameras generate a 360° panorama with overlapping angles of 6° between adjoining cameras (this is 1 m at a distance of 10 m). The horizontal field of view of the down looking cameras is reduced to 210° to avoid the operator being imaged on each panorama. Cameras 4 and 10 are the central cameras that can be used in the Trimble Access software as a video image to orientate the V10 Imaging Rover.
Panorama cameras cover the distance area larger than 5 m. The maximum distance used depends on the purpose and the accuracy requirements of the project. Distances of 30 m and more can reasonably be used. An object with a height of 10 m will be nearly covered by the panorama cameras at a distance of 20 m. To cover higher objects, you must increase the distance. Alternatively (or in addition), a rod tilt may be useful to enlarge the covered height. The section between 0.6 m and 6.6 m is covered by the down-looking cameras. An overlapping section in a sighting direction of 1.5 m is given between the camera groups.
The panorama cameras are inclined by about 2° to ensure an overlapping section with the field of view of the down-looking cameras.
The field of view of all cameras is 57.5° x 43°. The panorama cameras are arranged in a landscape orientation while the down-looking cameras in a portrait orientation. In this figure this is shown for cameras 4 and 10 that sight to the same horizontal direction.

Trimble V10 Imaging Rover: Intersection Angles

Products

• Trimble® V10 Imaging Rover

Question

Where I can get acceptable intersection angles with respect to a given baseline?

Answer

It is interesting to know in which area good intersection angles can be reached with respect to a given base line (identified here with red dots):

The graph is independent from a specific base length scale. It shows the geometry of intersection angles that is the same for all base lengths. Keep in mind that the above graph only demonstrates the 2D component. The interest object can often be on the baseline between the two stations, but if it is significantly below or above the station (for example, a power line) the optimum geometry will still be achieved.

Points with the same intersection angle are located on circles where the base line is a chord. You will get optimum intersection angles of 90° on a circle with the baseline being the diameter of the circle. The interesting area with acceptable intersection angles is located between the contour lines 30° and 150°. Points with intersection angles < 30° will result in unfavorable elongated error ellipses.

The diameter of the circle with the 30° intersection angles equals two times the baseline length b. Therefore, to get a 30° intersection, the distance to the point marked with the yellow dot must be less than twice the base length b. For a baseline length of 10 m the distance should be less than 20 m.