Digital Photogrammetry Various digital photogrammetry systems

V-Stars photogrammetry system V-STARS (video analog triangulation and research system) is a three-coordinate measurement system developed by GSI Company of the United States for industrial digital close-range photography. The system mainly has the advantages of high three-dimensional measurement accuracy (relative accuracy can reach1/200,000), high measurement speed, high degree of automation, and can work in harsh environment (such as thermal vacuum). It is the most mature commercial industrial digital photogrammetry product in the world.

The system is a large-scale coordinate measurement system based on digital photography, also known as industrial photogrammetry system, digital close-range photogrammetry system, digital close-range photogrammetry system, digital three-dimensional photogrammetry system and three-dimensional optical image measurement system.

It uses V-STARS software (as shown in Figure 3) to process the collected photos and get the three-dimensional coordinates of the points to be measured. These photos are obtained by shooting the same object in different positions and directions with high-precision professional cameras (such as INCA3 camera of GSI Company of the United States). V-STARS software will automatically process these photos, and get the accurate three-dimensional coordinates of the points to be measured through image matching and related mathematical calculations. Once processed, the three-dimensional data of the measured object will enter the coordinate system, just like it was measured or processed before. If necessary, V-STARS software also has built-in analysis tools, which can output 3D data. Generally, these measured objects are manually affixed with reflective signs in advance, or projected by points through point projectors, or detected by points on sticks. (1) High accuracy: the measurement accuracy of single camera system can reach 0.08mm in the range of 100 m, and that of double camera system can reach 0.17 mm; ;

(2) Non-contact measurement: the measurement method of optical photography, which does not contact the workpiece;

(3) Fast measurement speed: a single camera can complete a large number of point cloud measurements in a few minutes, and dual cameras can measure in real time;

(4) It can measure (temperature, vibration) in unstable environment: the measuring time is short, and it is less affected by temperature, so the dual camera system can measure in unstable environment;

(5) Especially suitable for measurement in narrow space: as long as the space is 0.5m, it can be photographed and measured;

(6) The data rate is high, and a large amount of data can be easily obtained: image points are automatically extracted and measured by computer software, and the speed of measuring 1000 points is almost the same as that of 10 points;

(7) Good adaptability: one system can measure the size of the measured object within the range of 0.5m to 100m;

(8) Good portability: single camera system 1 person can be carried to the site or other places for measurement. V-STARS system can be used for off-line and on-line measurement, namely, single camera system and dual (multi-) camera system, as shown in Figure 4. According to different cameras, it can be divided into V-STARS/S (intelligent single camera system), V-STARS/E (economical single camera system) and V-STARS/M (intelligent multi-camera system).

1 intelligent single camera system V-STARS/S

The main feature of intelligent single camera system is that it can not only provide high-precision measurement, but also be easy to carry.

At present, the latest model is V-STARS/S8, which mainly includes 1 measuring digital camera INCA3, 1 notebook computer (including system software), 1 set of benchmark ruler, 1 set of directional rod and 1 set of artificial characteristic marks (directional reflective marks), as shown in the figure.

(a)INCA3 camera (b) Software and accessories

Figure 5 V-STARS/S8 System Figure 6 Single Camera Measurement Process

INCA (Smart Camera) is a measuring smart camera independently developed by GSI. It uses a high-resolution CCD chip to collect images, and the built-in single-chip microcomputer can lossless compress and identify landmarks in real time. The solid integral fuselage is specially designed for the industrial field. Table 1 is the main technical parameters of the latest model INCA3a.

Table 1 INCA3a camera technical parameters

The system is mainly used for high-precision three-dimensional coordinate measurement of static objects. When measuring, you only need to take a certain number of digital photos from multiple positions and angles with a hand-held camera at a certain distance from the measured object (Figure 7), and then get the X, Y and Z coordinates of the characteristic landmark points through automatic processing (automatic positioning, automatic matching, automatic stitching and automatic adjustment of the image center calculation of the landmark points) by computer software.

The typical measurement accuracy (1 times sigma) of V-STARS/S8 system is improved from 5μ m+5μ m/m (using in C3 camera) to 4μ m+4μ m/m (using in C3 camera), that is, the measurement accuracy in the range of 10m reaches 0.044 mm ..

It should be emphasized that the main advantages of this system are portability and high precision. The whole system (including a computer, a camera and its accessories) can be packed in two boxes and can be carried around, which provides great convenience for your work.

Two economical single camera systems V-STARS/E

V-STARS/E is an entry-level single camera system of GIS company. This system is a better choice for the measurement users who are not very demanding on measurement accuracy but are relatively economical.

The latest model of economical single camera system is V-STARS/E4X, and the other configurations are exactly the same as V-STARS/S8 except that the camera adopts Nikon D2X, as shown in Figure 7. But for V-STARS/E4X system, it is impossible to upgrade to dual camera system.

The measurement accuracy of V-STARS/E4X system is10um+10um/m. ..

Figure 7 V-STARS/E4X system

The economical single camera system is mainly used for static objects with moderate measurement accuracy, because the measurement accuracy is relatively low by using general commercial cameras.

The main feature of this system is simple and portable, and compared with the expensive V-STARS/S8 system, this system has absolute price advantage. In addition, the photos taken with our Nikon D2X camera can be directly identified by V-STARS software, which is not only convenient, but also highly accurate.

3 intelligent multi-camera system V-STARS/M

The system is mainly used to provide real-time measurement under unstable measurement conditions.

The latest model of intelligent multi-camera system is V-STARS/M8, which can use two or more INCA cameras. The most commonly used dual-camera system mainly includes: two measuring digital cameras INCA3, 1 notebook computer (including system software), 1 set of benchmark ruler, 1 directional rod and 65438+. As shown in fig. 8.

When V-STARS/M8 dual cameras measure, the camera can be controlled by software to take pictures, which can simultaneously measure the characteristic mark points set on the measured object, and can also realize single-point measurement through the auxiliary measuring rod, which is especially suitable for the measurement of hidden points.

When V-STARS/M8 system is used together with the drip device (Figure 1 1), real non-contact measurement can be realized.

The figure 1 1 bidirectional+pointer is used for non-contact measurement of a large number of point clouds.

Because the camera exposure is controlled by the controller, the system is especially suitable for the measurement of dynamic objects, including deformation measurement. In addition, the full beam adjustment technology can achieve high-precision measurement even when the camera tripod is in an unstable environment (such as vibration). In the dynamic measurement mode, every time the camera moves, it takes photos of a group of landmark points on the measured object, but these points must be some stable control points on the object, so that the influence of camera movement on the measurement can be ignored. Generally speaking, this stable control field is established by a single camera system.

The typical measurement accuracy of V-STARS/M8 (dual camera) system is10um+10um/m. ..

Application of V-star system

V-STARS system is widely used in foreign aerospace, antenna manufacturing, automobile, shipbuilding, nuclear industry and many other fields. As shown in figure 12.