Ground resolution: is the ability to measure the minimum distance between remote sensing images that can differentiate between two adjacent land objects. After exceeding the resolution limit, two adjacent objects appear as a single target on the image.

data acquisition part

• Aviation film:
• As the name suggests, ground photos taken with an aerial photographer;
• Ground resolution:
• Ground resolution:
• can measure the minimum distance between remote sensing images (or images) that can differentiate between two adjacent land objects. After exceeding the resolution limit, two adjacent objects appear as a single target on the image (image). The resolution is usually expressed by the logarithm of black and white lines (line pairs/mm) that can be distinguished within a unit length. For scanned images, their resolution (i.e., the minimum area that can be distinguished) is usually expressed in the size of the cell.
• Aviation plate overlap rate:
• The overlap of two adjacent flights on the same route;

• Next overlap rate:
• Aviation overlap rate;

• Aerial Photo Scale:

When taking the average elevation of the photograph, the corresponding level on the ground, according to L, the ratio of the line segment l on the image to the corresponding level on the ground is the photography scale

where f is the main distance of the camera and H is Aerial High .

• Route Bend

Split the aerial camera film of the first jump route based on the image of the land object. The main point connection of each image is not on a straight line, but appears as a curved line, called the route bending. The curvature of the route is the percentage of the ratio of the maximum curvature vector of the route to the length of the route. Requires a route curvature of 3%

• -directional flight:
• refers to the five directions of the target when performing a three-dimensional model task of taking pictures and doing a three-dimensional model. The angle of the front, back, left and right routes is about -45° inclined, and the upper route is -90° orthographed;
• tic toe-shaped flight:
• same as above, perform two flight routes above the measurement area, with an angle of about -60°;
• becomes high (imitation ground) :
• UAV automatically generates a higher route according to the terrain of the measurement area, maintaining the consistent ground resolution;

• Orhythm:
• Aviation film taken when the lens of the drone is -90°
• Image rotation angle

Angle between the adjacent main point line on an image and the line connecting the frame mark in the same direction. The image rotation angle is required to be 6°. Excessively large image rotation angles will reduce the effective range of the stereo pair.

• center projection

Projection projection projection where rays converge at one point is called central projection.

• parallel projection

projection rays are parallel to a fixed direction projection.

oblique projection: projection rays obliquely and projection plane

orthophore projection: projection rays orthophores are orthophores.

aerial camera is the central projection, and the topographic map is orthogonal projection

• image point displacement

• When the image film is tilted and the ground is undulating, the position difference between the conformation of the ground points on the aerial camera relative to the ideal conformation. One of the main tasks of photogrammetry in

: convert the photographic scale aerial photograph taken by the ground according to the central projection law into an orthophoto-projected topographic map represented by the measurement map scale .

• Azimuth elements of the image film:
• Determines the position and posture parameters of the photography objective (photographic center) and the image film in the space set by the ground coordinate system , that is, the parameters that determine the relevant position between the three;
• Hot elements of the image film:
• represents the parameters of the position between the photography center and the image film: f, x0, y0;
• External orientation elements of the image film:
• represents the parameters of the position and posture of the photography center and image film in the ground coordinate system;
• is empty Intersection behind the intersection:

restores the beam during photography, that is, the spatial model is included in the earth coordinate system, and the corresponding outer orientation elements are solved through the known image point coordinates and their corresponding earth coordinate system (station coordinates: Xs, Ys, Zs; three corners: φ, ω, κ;);

• space front intersection:

On the premise of restoring the beam during photography, the coordinates under the earth coordinate system corresponding to the image point are solved through the collinear equation;



• Image control point measurement:

Image control point measurement is image control field measurement, measuring the ground coordinates of the ground point corresponding to the image control point.

generally stipulates that the error in the plane position of the nearest basic control point of
should not exceed 1/5 of the error in the plane position of the ground point. The error in the elevation of the
elevation control point and the flat high control point to the nearest basic control point should not exceed 1/l0 of the basic contour height distance.

• Aerial measurement Calculation formula
• Relative aerial height = Main distance f * Scale denominator m = f * m (1:m)
• reference plane height = (highest point + lowest point)/ 2　　
• Absolute aerial height = Datum height + relative aerial height
• m = Ground resolution / Cell size
• Lx photo width; Ly photo height;
• p heading overlap; q side overlap;
• photography baseline B = Lx*m*(1-p);
• route interval D = Ly*m*(1-q);
• partition route lines = partition width / D;
• photos per route = route length (partition length)/ B;
• Because both ends require no less than 1 baseline to exceed the boundary of the shooting area, 2B
• total number of photos = number of partitioned routes * Number of photos per route
• Number of photos per route
• Number of shooting area models = number of partitioned routes * (Number of photos per route - 1)

▐ Data processing part

• aerial scale

Definition in Photogrammetry: Aerial scale is the ratio of the horizontal distance between the line segment l on the aerial image and the corresponding ground line segment L:



m is the denominator of the aerial scale, f is the main distance (focal length) of the camera, and H is the photography height or aerial height of the average elevation plane. The aerial height here is generally the relative aerial height relative to a certain level.

• Air 3:
• Full name is Aerial triangulation . It is a measurement method for the control point encryption in stereophotographic measurement based on a small number of field control points, and the measurement method of the encrypted point elevation and plane position of the encrypted point are obtained;
• GSD Relationship with flight altitude:

Flight altitude is inversely proportional to the ground image resolution, and the higher the flight, the lower the ground image resolution.



H is the flight altitude, f is the lens focal length, a is the cell size, GSD is the ground image resolution

• Selection of analytical scale

2 9

Into the graph scale	aerial scale	ground resolution (m)	ground sampling interval	ground sampling interval GSD/cm
:500	:2000~1:3500	.1	~7
:1000	~14	:3500~1:7000	.1	~14	~14	~14
:2000	:7000~1:14000	.2	4~28
:5000	:10000~1:12000 html l31	.5	0~40
:10000	:12000~1:40000	.0	0~80
: 25000	: 25,000 ~ 1: 60,000	.5	0 ~ 120
: 50,000	: 35,000 ~ 1: 80,000	: 35,000 ~ 1: 80,000	.0	0~160

• Large, medium and small scale topography map

Large scale topography map : 1:500-1:10000

Medium scale topography map: 1:25000-1:100000

Small scale topographic map: 1:250000-1:1000000

• :500, 1:1000, 1:2000 Topographic map



• DEM:
• Digital elevation model (Digital) Elevation Model, referred to as DEM, is a digital simulation of ground terrain (i.e., digitized expression of terrain surface morphology) through limited terrain elevation data. It is a physical ground model that represents ground elevation in a set of ordered numerical arrays. It is a branch of the Digital Terrain Model (DTM), and other various terrain eigenvalues ​​can be derived from this;



• DSM:
• Digital Surface Model (Digital Surface) Model, abbreviation DSM) refers to a ground elevation model that contains the heights of surface buildings, bridges and trees. Compared with DEM, DEM only contains the elevation information of the terrain and does not contain other surface information. DSM further covers the elevation of other surface information other than the ground based on DEM. In some areas where there is a demand for building height, it has received great attention;
• DTM:
• DTM (Digital Terrain Model) - The digital terrain model is a simulated representation of continuous ground using a large number of coordinate points of known x, y, and z selected in an arbitrary coordinate system. In other words, DTM is a digital expression of the morphological attribute information of the terrain surface, and a digital description with spatial position characteristics and terrain attribute characteristics. x and y represent the plane coordinates of the point, and the z value can represent information such as elevation, slope, temperature, etc. When z represents elevation, it is a digital elevation model, namely DEM (Digital Elevation Model). The attribute information of the terrain surface morphology generally includes elevation, slope, slope direction, etc.
• DOM and TDOM:
• DOM-Digital Orthophoto Map (DOM, Digital Orthophoto Map) is a digital orthophoto set generated by performing digital differential correction and mosaicing of aviation (or aerospace) photos and cropping them according to a certain range of images. It is an image with both map geometric accuracy and image characteristics.
• DLG:
• DLG (Digital Line Graphic) is a vector data set of map elements that are basically consistent with existing line drawings, and it saves the spatial relationship information and related attribute information between each element. It is a type of 4D product.



• D product:
• With the combination and continuous development of surveying and mapping technology and computer technology, maps are no longer limited to the previous modes. Modern digital maps are mainly composed of DOM (digital orthogram image), DEM (digital elevation model), DRG (digital grid map), DLG (digital line drawing map) and composite mode.