JP2019020371A - Aircraft indicator for orientation and calibration of aircraft-mounted camera and laser range finder - Google Patents

Abstract

To provide an aircraft indicator as an index for orientation of giving ground coordinates and for calibration of obtaining a positional relationship with a direct orientation device to an altitude point group measured by photograph taken with aircraft-mounted camera and laser range finder.SOLUTION: The aircraft indicator used for orientation in aerial laser surveying is provided with a side plate for easily reading the shape of the top board. The aircraft indicator is also provided with a cone-shaped body which is attached on a top plate for clarifying three-dimensional shape of the aircraft indicator in order to facilitate three-dimensional analysis of a displacement of the aircraft indicator on a piece of data observed from plural directions. Photographing and laser ranging from extremely low altitude made it possible to receive sunlight or laser beam reflected by a small reflector. Reflectors are provided around the position of the ground coordinate to obtain data clearer than the other area. With this, the position of the aircraft indicator can be easily and automatically detected from aerial photograph and altitude point groups.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an index for calibration that obtains a positional relationship with an orientation that gives ground coordinates to an altitude point group that is mounted on an aircraft and that is taken by a camera or an altitude point group measured by a laser rangefinder.

  In topographic map creation, aerial photogrammetry using aerial photographs taken from aircraft has become widespread as a standard technique because a wide area can be created with uniform accuracy (see Reference 1).

  In aerial photogrammetry, a sign called an anti-air sign is installed as an index for giving ground coordinates to the aerial photograph, and ground coordinates are given to the anti-air sign. By observing the anti-air signs with the ground coordinates on the aerial photograph, the orientation that gives the position and inclination in the ground coordinate system to the aerial photograph, the aerial that gives the position and inclination in the ground coordinate system to multiple aerial photographs at once Triangulation has been carried out. Aerial triangulation is a method of orientation.

  In recent years, a direct positioning device consisting of a satellite positioning device using a positioning satellite such as a GPS satellite and an inertial measurement device incorporating an accelerometer or angular velocity meter is installed in an aircraft, and the position in the ground coordinate system is displayed in an aerial photograph. However, in order to correct the deviation between the coordinate system by satellite positioning and the ground coordinate system, an anti-air sign is necessary.

  Aviation laser surveying, which is equipped with a laser rangefinder instead of a camera and maintains the height of the terrain as a high-density altitude point group, is also popular, but it is used daily with the height obtained by satellite positioning In order to match the height obtained by leveling, an anti-air sign called an adjustment reference point is required (see Document 1).

  In order to give the camera and laser rangefinder the position and tilt in the ground coordinate system from the data observed by the direct location device, the relationship between the direct location device and the camera, or the direct location device and the laser rangefinder is used in the orientation software. Need to give. This relationship is obtained by a calibration operation in which the position and inclination given from the direct localization apparatus are compared with the position and inclination determined from the anti-air sign by photographing or ranging the anti-air sign (see Document 2).

  Anti-air signs used for aerial photogrammetry are standardly equipped with feet that are high enough to prevent the surrounding grass from being covered by the grass that extends after installation. May be used.

  Anti-air signs used for aerial photogrammetry may have a pattern such as a triangle with a vertex at the given ground coordinate or a checkered pattern with an intersection to make it easier to recognize where the ground coordinate is given. .

  Orientation and calibration can use the same form of anti-air signs.

In air-to-air signs used for aerial laser surveying, a flat area of several meters square is used for orientation, and a large building with a rectangular roof is used for calibration.
In aerial laser surveying, the distance between altitude points that can be measured is as wide as several tens of centimeters, so a large flat land or a large building is required.

Reference 1

“Work Rules” March 31, 2016 Ministry of Land, Infrastructure, Transport and Tourism Notification No. 565

Reference 2

“Quality evaluation of aerial laser surveying” Kosuke Tsudome, Tamotsu Nakajima, Teruyoshi Fujiwara Photogrammetry and remote sensing Vol. 41, no. 1, 2002

The resolution of the camera has been improved, the range of the laser rangefinder can be shortened, and unmanned aircraft capable of flying at low altitudes that can take advantage of these improvements has emerged. Taking high-resolution aerial photographs and creating high-density elevation point clouds (see Reference 3).
As the resolution of aerial photographs increases and the density of elevation points increases, the size and shape required for anti-air signs also differ.
However, there are aspects that cannot be adapted to new environments simply by reducing the size.

When shooting from an ultra-low altitude, the height of the anti-air sign relative to the flight altitude of the aircraft is relatively high, and the lower the anti-air sign becomes clearer the closer to the end of the aerial photograph.
Although aerial photographs are taken more than 60 percent along with the flight of the aircraft, the way in which aerial signs are reflected in the aerial photographs varies from aerial photographs.
When shooting from an ultra-low altitude, the resolution of aerial photographs may become high, and the difference in how the anti-air signs are captured for each aerial photograph becomes clearer.
In this way, the same anti-air sign appearing differently for each aerial photograph hinders the observation of the anti-air sign by automatic processing using computer software.

Laser ranging from an ultra-low altitude enables high-density ranging, so the size of the anti-air sign can be reduced and it is economical.
In laser ranging from an extremely low altitude, the area to be measured is narrowed. In narrow target areas, the places where anti-air signs can be installed are limited. Since the possibility of selecting a flat place is reduced as in conventional aerial laser surveying, installation of anti-air signs with feet is effective.
However, if an anti-air sign is installed with a foot attached, laser ranging will also be performed under the anti-air sign.
A multi-path is generated in which the laser light measured near or directly below the anti-air sign is reflected and hits the back side of the anti-air sign and returns to the laser rangefinder through the path on which the reflected light has entered.
Laser ranging under these anti-air signs and multipath laser ranging makes it difficult to distinguish the top plate of the anti-air sign from the altitude correctly measured by laser.
Increasing the length of the anti-air sign will lead to the solution, but this will not be an essential solution because it will increase the cost of materials, increase the load related to storage and transportation, decrease the installation accuracy, etc. .

Laser ranging from an ultra-low altitude enables high-density ranging, so that the air-to-air sign used for calibration can also be reduced.
In laser ranging from an extremely low altitude, the area to be measured is narrowed. In a narrow target area, it is difficult to use a building with a rectangular roof as in conventional aerial laser surveying, so it is necessary to install it by itself. In a narrow target area, instead of a shape such as a building having a rectangular roof, it is also necessary to have a shape that can efficiently calculate the positional relationship between the direct positioning device and the laser rangefinder.

Reference 3

"Public survey manual using UAV (draft)" March 2017 Ministry of Land, Infrastructure, Transport and Tourism Geographical Survey Institute

Means for solving the problem

The anti-air sign is photographed so that the bottom of the anti-air sign is reflected, the distance is measured under the anti-air sign, and the laser light that is measured under and around the anti-air sign is reflected to avoid multipath on the back side of the anti-air sign. The side plate is installed on the side where the anti-air sign is measured.
The front direction of the anti-air sign may be covered with a side plate.
The color may be changed or a pattern may be added so that the difference between the top plate and the side plate becomes clear.

A cone whose shape is clear from the laser-measured data is placed on the anti-air sign. The cone is not a perfect shape and may be only on the side where laser ranging is performed.
Ground coordinates are given to the tip of the cone.
The tip of the cone does not have to coincide with the center of the antiaircraft sign.

A reflector is placed at the position where the ground coordinates are given, usually at the center of the anti-air sign.
The reflector may have a hole in the center. In the case where there is no hole, it is assumed that the center of the reflecting plate is pasted to the position where the ground coordinates are given by a scissors or the like.
Shooting and observation may be performed from an ultra-low altitude, and even a small reflector will appear brighter than others, or it will be easier to observe strong reflection intensity, making it easier to find the position of anti-air signs using automatic processing. .

BEST MODE FOR CARRYING OUT THE INVENTION

  Hereinafter, an embodiment of a method for creating an anti-air sign according to the present invention will be described with reference to the drawings.

Top plate The anti-air sign of the present invention is made of a material such as thick wood that does not distort even if supported by a pile from below. FIG. 1 is a diagram in which feet are installed and a three-blade-shaped anti-air sign with only a top plate away from the ground is installed.
The shape of the anti-air sign shall be either a regular polygon, a circle, or a blade shape with a side plate attached. The one with a cone is either a regular polygon or a circle.
The size of the anti-air sign is determined according to the scale of the aerial photograph to be taken and the interval of the laser light to be measured, and is set to a scale and an interval that can be clearly recognized on the aerial photograph or the altitude point group.

Side Plate FIG. 2 is a diagram of an anti-air sign in a circle, square, or four-blade shape with a side plate attached.
The side plate is attached to the side of the top plate of the anti-air sign on the side where it is shown in the aerial photograph or the side where the distance is measured with laser light. Install.
The width of the side surface is a length that can be measured by several pixels or more when shooting in an aerial photograph, and can measure a distance of several or more points when measuring with laser light.

FIG. 3 is a diagram in which a cone is installed on a circular top plate and a quadrangular pyramid is installed on a square top plate.
Place the cone on the top of the anti-air sign so that the cone is stable.
The shape of the cone may be a pyramid or a cone, and only the side surface on which the laser beam is irradiated may be actually installed.
The side surface of the cone is installed on the side where the laser light is measured, and covers the entire surface when the distance measurement is performed from all directions around the anti-air sign.
The size of the cone is set such that the shape of the cone can be sufficiently expressed by the altitude point group obtained by laser ranging. Moreover, it may be the same as the size of the top board.

Reflector FIG. 4 is a diagram in which a reflector is installed at the center of the circular top plate and at the apex of the cone.
At the center of the top plate, a reflector that reflects the sunlight in the aerial photograph and appears very bright, or reflects the laser beam very strongly is installed.
As for the shape of the reflector, a center such as a regular polygon or a circle can be specified, and a hole may be formed in the center. Those that are not perforated shall not break even if they are attached to the top plate with a scissors or the like so that the centers of the top plate and the reflecting plate coincide with each other.
The size of the reflector is such that it is projected to several pixels or more when photographed in an aerial photograph, and is dimensioned to irradiate several points or more when illuminated with laser light.

The structure of the side plate and the cone may be assembled to the top plate in the field or may be pre-installed on the top plate, but is preferably assembled for transportation and storage.
The side plate and the cone itself may also be constituted by several parts and assembled.

  The created anti-air signs are placed on the ground so that they will not come off or be distorted by a slight impact using piles.

The ground coordinates are given by the reference point survey to the center of the top of the installed anti-air sign or the apex of the cone.
The ground coordinates may be a geodetic coordinate system defined by the country or an arbitrary coordinate system set by the user.

  Where the ground coordinates are given, a reflector having a size corresponding to the size of the ground pixel size and the interval for laser ranging is installed.

Effect of the invention

  As described above, in the present invention, in addition to the top plate of the anti-aircraft sign, a side plate is provided, and the side plate can be provided with a color or a pattern different from the top plate, The shape of the top plate of the anti-air sign becomes clear, and it becomes easy to recognize the position where the ground coordinates are installed.

In addition to the top plate of the anti-aircraft sign, a pyramid is provided on the top plate, so that the shape of the anti-air sign at the elevation point group obtained by laser ranging becomes clear and the position where the ground coordinates are installed is recognized. It becomes easy.
By comparing the altitude point groups obtained by flying the aircraft from different directions by laser ranging, the positional relationship between the localization device and the laser ranging probe can be calibrated directly.

  By attaching a reflector at the position where the ground coordinates on the anti-air sign are installed, only that part is brighter than the others, so detection by automatic processing is facilitated.

  It is the figure which installed the three-blade-shaped anti-air sign only of a top plate away from the ground by installing a foot.   It is a figure of the anti-air sign of a circle, a rectangle, and a four-blade shape to which a side plate is attached.   It is the figure which respectively installed the cone on the circular top plate and the quadrangular pyramid on the quadrangular top plate.   It is the figure which installed the reflecting plate in the center of a circular top plate, and the conical vertex, respectively.

1 Top plate 2 Feet 3 Position where ground coordinates are attached 4 Side plate 5 Cone 6 Reflector

Claims (3)

  An anti-air sign characterized by attaching a side plate to the top plate.   An anti-air sign characterized by attaching a cone to the top plate.   An anti-air sign, characterized in that a reflector is attached to the position where the ground coordinates are attached.

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