CN102426010B - Method for generating variable resolution digital elevation model - Google Patents

Abstract

The invention relates to a method for generating a variable resolution digital elevation model. The method comprises the following steps of: establishing an east-north-sky right-handed coordinate system according to a measured topographic region, establishing a new plane coordinate system X'O'Y' in an XOY plane by using a measurement station point as a center, and establishing a polar coordinate system by using the original point of the new plane coordinate system as a pole and the direction far away from the center of the measurement station point as a polar axis; acquiring a three-dimensional data discrete point of the measured topographic region under the east-north-sky right-handed coordinate system; determining an angle sampling range in the polar coordinate system according to the measured topographic region, setting angle sampling intervals, and calculating the quantity of elevation sampling points required in the angle range; determining a radial sampling range along each angle direction, determining radial sampling change rates and sampling intervals, and calculating the quantity of the elevation sampling points required in the radial direction; and acquiring polar coordinates of all the elevation sampling points within the angle sampling range and the radial sampling range, constructing an irregular triangulation network according to the data discrete point, and calculating through interpolation to obtain elevation values of all the elevation sampling points. The method can be widely applied to data storage and expression during topographic and geomorphic measurement.

Description

A kind of generation method of variable resolution digital elevation model

Technical field

The present invention relates to a kind of generation method of digital elevation model, particularly express about a kind of digital elevation model that is applicable to obtain by close-range photogrammetry or territorial laser scanning, and can keep the generation method of the variable resolution digital elevation model of the different vertical accuracies of initial landform.

Background technology

Digital elevation model (DEM) is to utilize one group of orderly terrain sampling point digitized representations topographical surface.Digital elevation model commonly used in prior art comprises regular grid (Grid) and TIN (TIN).Regular grid is that the overlay area with digital elevation model is divided into regularly arranged square graticule mesh, store the height value of each graticule mesh central spot, and record position and the mesh spacing of Fixed Initial Point, can calculate with the ranks number process of corresponding matrix element the planimetric position of arbitrary grid point and obtain, its shortcoming is to be difficult to definite suitable resolution (graticule mesh size) to express various topography and landform characters, because the overall situation is all used same resolution, if adopt higher resolution, landform easily produces mass of redundancy data for utilizing close-range photogrammetry to measure at a distance; If the employing low resolution is unfavorable for expressing the feature of landform nearby, lost the precision of landform nearby.The sealene triangle net is comprised of continuous triangular facet, can estimate preferably the morphologic characteristics dotted line, the fluctuating feature of expression complex-terrain true to nature, and can overcome the problem that topographic relief changes little area generation redundant data.The sealene triangle net comprises a large amount of data points, the surface just needs a small amount of data point when single, large due to sealene triangle network data amount, data structure is complicated, generally be only applicable among a small circle, large scale, high-precision terrain modeling, during generally as generating digital elevation model, interpolation is used.

When utilizing close-range photogrammetry or territorial laser scanning that landform is measured, the precision of surveying the topography presents certain rule with variable in distance, far away its of the distance measurement point precision of surveying the topography is lower, regular grid is to use same resolution regular grid, the landform accuracy table can only be reached an accuracy standard, can not change according to landform precision height, TIN has just recorded the elevation of some discrete points, resolution is random to be followed, and both all can not express the characteristics of the terrain data that utilizes close-range photogrammetry or territorial laser scanning acquisition effectively.

Summary of the invention

For the problems referred to above, the purpose of this invention is to provide a kind of digital elevation model that can effective expression utilizes close-range photogrammetry or territorial laser scanning to measure, and can distinguish to the variation that the data that obtain are carried out irredundant storage the generation method of digital elevation model.

For achieving the above object, the present invention takes following technical scheme: a kind of generation method of variable resolution digital elevation model, comprise the steps: 1) according to foundation east-north, landform zone of surveying-day right-handed coordinate system, and set up a new plane coordinate system X ' O ' Y ' with survey station dot center in the XOY plane of east-north-day right-handed coordinate system, take the initial point of new plane coordinate system as limit, take away from survey station dot center direction as pole axis, set up a polar coordinate system; 2) utilize close-range photogrammetry or territorial laser scanning to obtain the three-dimensional data discrete point in the institute's geodetic shape zone under described east-north-sky right-handed coordinate system; 3) definite angle sample range regional according to the landform of surveying in polar coordinate system, set angle sampling interval, and the quantity of the interior required elevation sampled point of calculating angular range; 4) determine the interior radially sample range along each angle direction of angular range, calculate the polar coordinates of radially required elevation sampled point, and calculate the quantity of radially required elevation sampled point; 5) in the angle sample range with radially obtain the polar coordinates of all elevation sampled points under polar coordinates in sample range, be angle coordinate and the radial coordinate of elevation sampled point, by described step 2) data discrete point build TIN, calculate the height value of each elevation sampled point by the TIN interpolation.

Described step 4) concrete grammar is as follows: 1) smallest radial coordinate and the maximum radial coordinate of determining elevation sampled point each angle direction on regional according to the landform of required measurement; The ground elevation precision of 2) sampling according to measuring accuracy and the needs of close-range photogrammetry or territorial laser scanning ground elevation is set up the rate of change λ of digital elevation model resolution, λ is m/f, f is the focal length of the surveying instrument that adopts in close-range photogrammetry or territorial laser scanning, wherein, m is that pixel quantity and f and m are pixel and represent; 3) calculate the polar coordinates of radially required elevation sampled point, and calculate the quantity of radially required elevation sampled point, concrete grammar is as follows: 1. according to formula r _j=r _min(1+ λ) ^j-1Calculate the radial coordinate of all elevation sampled points on each angle direction, r _minBe the smallest radial coordinate of the elevation sampled point on each angle direction, λ is the rate of change of digital elevation model resolution; 2. calculate the radially elevation sampled point quantity of each angle direction.

Described step 5) concrete grammar is as follows: the coordinate figure that 1. polar coordinates of each elevation sampled point is converted into east-north-sky right-handed coordinate system; 2. the three-dimensional data discrete point according to institute's geodetic shape zone builds TIN, on the basis that builds TIN by gram in golden interpolation method obtain the height value of each elevation sample point; 3. the corresponding height value that 2. the elevation sample point coordinate value that described step is obtained in 1. and described step obtain adopts the data structure storage of variable resolution digital elevation model in data file.

described step data file 3. comprises header file and data file, described header file stores the coordinate of variable resolution digital elevation model survey station central point under east-north-day right-handed coordinate system, the coordinate of variable resolution digital elevation model survey station central point under east-north-day right-handed coordinate system, variable resolution digital elevation model start angle value and angle up-sampling quantity, variable resolution digital elevation model is initial value and elevation sampled point quantity radially radially, variable resolution digital elevation model change resolution rate and radial values keep decimal digits and variable resolution digital elevation model null value, store the height value of each elevation sampled point of variable resolution in described data file.

the present invention is owing to taking above technical scheme, it has the following advantages: 1, utilize close-range photogrammetry or territorial laser scanning that institute's geodetic shape zone is measured, presenting certain rule for the precision of surveying the topography with variable in distance is the lower characteristics of distance measurement point its precision of surveying the topography far away, the present invention is in the angle sample range and radially obtain each elevation sampled point in sample range, each elevation sampled point carries out by the TIN with the discrete data generation that measures the height value that interpolation obtains each elevation sampled point, effectively kept the full accuracy by close-range photogrammetry or resulting each distance elevation of territorial laser scanning.2, the present invention adopts the data structure of variable resolution digital elevation model that the measurement data that obtains is stored, and not only can effectively eliminate the data redundancy of conventional grid-net type digital elevation model storage and reduce memory data output.The present invention can be widely used in the storage of topography and geomorphology measurement data and expression.

Description of drawings

Fig. 1 is the generation method flow schematic diagram of variable resolution digital elevation of the present invention;

Fig. 2 is the conceptual schematic view of variable resolution digital elevation model of the present invention.

Embodiment

Below in conjunction with drawings and Examples, the present invention is described in detail.

The present invention obtains by close-range photogrammetry or territorial laser scanning the generation method that variation is distinguished digital elevation model, comprises the following steps (as shown in Figure 1):

1, according to foundation east-north, landform zone of surveying-day right-handed coordinate system, and set up a new plane coordinate system X ' O ' Y ' in the XOY plane of east-north-day right-handed coordinate system, set up a polar coordinate system (as shown in Figure 2) take the initial point of new plane coordinate system as limit.

take the east in institute's geodetic shape zone to as X-axis, to the north of direction be Y-axis, take the direction that points into the sky perpendicular to XOY plane as Z axis, set up east-north-day right-handed coordinate system (being the O-XYZ coordinate system), set up a new plane coordinate system X ' O ' Y ' take survey station dot center as initial point in the XOY plane of east-north-day right-handed coordinate system, take the initial point of new plane coordinate system X ' O ' Y ' as limit, initial zero direction take the direction that is parallel to X ' axle as polar coordinate system, to set up a polar coordinate system away from survey station dot center direction for pole axis O ' r radially, definition is the positive dirction of angle along the counter clockwise direction of initial zero direction, the angular range of selected polar coordinate system is 0～360 °.

2, as shown in Figure 1, utilize close-range photogrammetry or territorial laser scanning to obtain the three-dimensional data discrete point in the institute's geodetic shape zone under east-north-day right-handed coordinate system.

3, determine the angle sample range according to the landform surveyed zone in polar coordinate system, the set angle sampling interval is also calculated the quantity of required elevation sampled point in angular range.

Along angle direction equal interval sampling in angular range of polar coordinate system, be at first θ according to the definite required sampling angle scope in institute's geodetic shape zone _min(starting point of angle sampling) and θ _max(end point of angle sampling), the resolution of the digital elevation model that then generates is as required determined angular sampling interval δ _θ, the angle coordinate that obtains i elevation sampled point is:

θ _i＝θ _min+i·δ _θ (1)

Calculate the number of samples θ of angle direction in the sampling angle scope of institute's geodetic shape _MFor:

θ _M＝INT((θ _max-θ _min)/δ _θ)+1 (2)

Wherein, in following formula, INT is rounding operation.

4, definite radially sample range along each angle direction, the polar coordinates that calculate radially required elevation sampled point also calculate the quantity of radially required elevation sampled point.

1) the smallest radial coordinate r that determine elevation sampled point each angle direction on regional according to the landform of required measurement _minWith maximum radial coordinate r _max(r _min＞0);

2) measure the precision (being the precision of surveying instrument) of ground elevation according to close-range photogrammetry or territorial laser scanning and need the ground elevation precision of sampling to set up the rate of change λ of digital elevation model resolution, rate of change λ value in close-range photogrammetry of resolution is generally m/f, wherein, f is the focal length of the surveying instrument that adopts in close-range photogrammetry, m is pixel quantity, f and m are pixel and represent, generally the m span is 1～f, the numerical value of the rate of change λ of the resolution of the surveying instrument that adopts in territorial laser scanning is determined identical with the obtaining value method of close-range photogrammetry, do not repeat them here.

3) definite radial coordinate in the radial direction and elevation sampled point quantity along each angle direction, concrete grammar is as follows:

1. the radial coordinate of supposing the 1st elevation sampled point on a certain angle direction is r _min, the resolution that obtains the digital elevation model of this elevation sample point is Δ _min=λ r _min, according to radial coordinate and the resolution ax/of this elevation sampled point _minObtain along the radial coordinate r of second elevation sampled point of this angle direction ₂For:

r ₂＝r _min+Δ _min＝r _min+λ·r _min＝r _min(1+λ) (1)

The radial coordinate that obtains thus j elevation sampled point on this angle direction is r _j, the resolution of j elevation sampled point radial coordinate place digital elevation model is Δ _j=λ r _j, obtain the radial coordinate r of j+1 elevation sampled point _j+1For:

r _j+1＝r _j+Δ _j＝r _j+λ·r _j＝r _j(1+λ)＝r _min(1+λ) ^j (2)

2. according to above-mentioned steps 1., can obtain along the radial coordinate of arbitrary elevation sampled point j in the radial direction of each angle direction be:

r _j＝r _min(1+λ) ^j-1 (5)

Unified for guaranteeing precision, set r _jThe reservation decimal digits be β.

3. the footpath of determining each angle direction elevation sampled point quantity r that makes progress _NFor:

$r_N=\mathrm{INT}\left({\log }_{(1+\mathrm{\λ})}^{(r_{\max }/r_{\min })}\right)+1=\mathrm{INT}\left(\frac{\lg \frac{r_{\max }}{r_{\min }}}{\lg (1+\mathrm{\λ})}\right)+1---\left(3\right)$

5, change to above-mentioned angle direction with along angle coordinate and radial coordinate that the polar coordinates that the radially sampling of angle direction obtains each elevation sampled point under polar coordinates namely obtain the elevation sampled point, the three-dimensional data discrete point that above-mentioned steps is obtained builds the triangulation network, calculate the height value of each elevation sampled point by triangulation network interpolation, concrete grammar is as follows:

1. with each the elevation sampled point (θ in polar coordinate system _i, r _j) be converted into the coordinate under east-north-sky right-handed coordinate system $(X_{({\mathrm{\θ}}_i,r_j)},Y_{({\mathrm{\θ}}_i,r_j)}):$

$\left\{\begin{array}{c}{X}_{({\mathrm{\θ}}_i,r_j)}=r_{\min }{(1+\mathrm{\λ})}^{j-1}\cos ({\mathrm{\θ}}_{\min }+i\·{\mathrm{\δ}}_{\mathrm{\θ}})\\ Y_{({\mathrm{\θ}}_i,r_j)}=r_{\min }{(1+\mathrm{\λ})}^{j-1}\sin ({\mathrm{\θ}}_{\min }+i\·{\mathrm{\δ}}_{\mathrm{\θ}})\end{array}\right.i,j=\mathrm{1,2},...---\left(4\right)$

2. utilize the three-dimensional data discrete point in institute's geodetic shape zone to build TIN, on the basis that builds TIN by gram in golden interpolation method obtain each elevation sampled point

The height value at place

3. adopt the data structure storage of variable resolution digital elevation model in data file the coordinate figure under the east-north of all elevation sampled points-sky right-handed coordinate system and corresponding height value, the data structure of the data of storage is comprised of header file and data file two parts, and concrete data store organisation is as follows:

Header file:

VrDEM X.X//VrDEM is the file identification of variable resolution digital elevation model, and X.X is version number, initial version 1.0

The coordinate of Xo Yo // variable resolution digital elevation model survey station central point under east-north-day right-handed coordinate system

θ _minθ _m// variable resolution digital elevation model start angle value and angle up-sampling quantity

r _minr _N// variable resolution digital elevation model is initial value and elevation sampled point quantity radially radially

The decimal digits that the rate of change of λ β // variable resolution digital elevation model resolution and radial values keep

-99999 //NODATA, the variable resolution digital elevation model null value

Data file:

$\begin{array}{cccccc}{Z}_{\mathrm{1,1}}& Z_{\mathrm{1,2}}& ...& Z_{1,r_j}& ...& Z_{1,r_N}\\ Z_{\mathrm{2,1}}& Z_{\mathrm{2,2}}& ...& Z_{2,r_j}& ...& Z_{2,r_N}\\ ...& ...& ...& ...& ...& ...\\ Z_{{\mathrm{\θ}}_i,r_1}& Z_{{\mathrm{\θ}}_i,r_2}& ...& Z_{{\mathrm{\θ}}_i,r_j}& ...& Z_{{\mathrm{\θ}}_i,r_N}\\ ...& ...& ...& ...& ...& ...\\ Z_{{\mathrm{\θ}}_M,1}& Z_{{\mathrm{\θ}}_M,2}& ...& Z_{{\mathrm{\θ}}_M,r_j}& ...& Z_{{\mathrm{\θ}}_M,r_N}\end{array}$ // variable resolution elevation point value

The present invention can obtain by above-mentioned formula (7) polar coordinates and the height value of each elevation sampled point after adopting the variable resolution digital elevation model storage easily.

The various embodiments described above only are used for explanation the present invention, and wherein the step of digital elevation model generation method can change to some extent, and every equivalents of carrying out on the basis of technical solution of the present invention and improvement all should not got rid of outside protection scope of the present invention.

Claims (3)

1. the generation method of a variable resolution digital elevation model, comprise the steps:

1) according to foundation east-north, landform zone of surveying-day right-handed coordinate system, and set up a new plane coordinate system X ' O ' Y ' with survey station dot center in the XOY plane of east-north-day right-handed coordinate system, take the initial point of new plane coordinate system as limit, take away from survey station dot center direction as pole axis, set up a polar coordinate system;

2) utilize close-range photogrammetry or territorial laser scanning to obtain the three-dimensional data discrete point in the institute's geodetic shape zone under described east-north-sky right-handed coordinate system;

3) definite angle sample range regional according to the landform of surveying in polar coordinate system, set angle sampling interval, and the quantity of the interior required elevation sampled point of calculating angular range;

4) determine the interior radially sample range along each angle direction of angular range, calculate the polar coordinates of radially required elevation sampled point, and calculate the quantity of radially required elevation sampled point, its step is as follows:

(1) smallest radial coordinate and the maximum radial coordinate of determining elevation sampled point each angle direction on regional according to the landform of required measurement;

The ground elevation precision of (2) sampling according to measuring accuracy and the needs of close-range photogrammetry or territorial laser scanning ground elevation is set up the rate of change λ of digital elevation model resolution, λ is m/f, f is the focal length of the surveying instrument that adopts in close-range photogrammetry or territorial laser scanning, wherein, m is that pixel quantity and f and m are pixel and represent;

(3) calculate the polar coordinates of radially required elevation sampled point, and calculate the quantity of radially required elevation sampled point, concrete grammar is as follows:

1. according to formula r _j=r _min(1+ λ) ^j-1Calculate the radial coordinate of all elevation sampled points on each angle direction, r _minBe the smallest radial coordinate of the elevation sampled point on each angle direction, λ is the rate of change of digital elevation model resolution, r _jRadial coordinate for j elevation sampled point on angle direction;

2. calculate the radially elevation sampled point quantity of each angle direction;

5) in the angle sample range with radially obtain the polar coordinates of all elevation sampled points under polar coordinates in sample range, be angle coordinate and the radial coordinate of elevation sampled point, by described step 2) data discrete point build TIN, calculate the height value of each elevation sampled point by the TIN interpolation.

2. the generation method of a kind of variable resolution digital elevation model as claimed in claim 1, it is characterized in that: the concrete grammar of described step 5) is as follows:

1. the polar coordinates of each elevation sampled point are converted into the coordinate figure of east-north-sky right-handed coordinate system;

2. the three-dimensional data discrete point according to institute's geodetic shape zone builds TIN, on the basis that builds TIN by gram in golden interpolation method obtain the height value of each elevation sample point;

3. the corresponding height value that 2. the elevation sample point coordinate value that described step is obtained in 1. and described step obtain adopts the data structure storage of variable resolution digital elevation model in data file.

3. the generation method of a kind of variable resolution digital elevation model as claimed in claim 2, it is characterized in that: described step data file 3. comprises header file and data file, described header file stores the coordinate of variable resolution digital elevation model survey station central point under east-north-day right-handed coordinate system, variable resolution digital elevation model start angle value and angle up-sampling quantity, variable resolution digital elevation model is initial value and elevation sampled point quantity radially radially, variable resolution digital elevation model change resolution rate and radial values keep decimal digits and variable resolution digital elevation model null value, store the height value of each elevation sampled point of variable resolution in described data file.

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