UAV 1000 scale basic surveying and mapping application case 

1:1000 digital line drawing of urban planning project in a district of central China

Project Description:

In 2016, Wuhan Visiontek Technology Co., Ltd. undertook the production of 1:1000 digital line drawing of an urban planning project in a district of Central China, with the terrain being a plain area.

The project uses Visiontek's latest drone rare control solution:

Hardware: Fixed-wing UV16+Dual-axis PTZ+Dual-frequency differential GPS+Canon 5D3+35mm lens

Software: Air triangle encryption HAT1.0+patb

Dual-frequency GPS solution Trip1.0

MapMatrix4.2

Project Description:

Provide 1:1000 scale digital line drawing results, the plane coordinate system adopts the CGCS2000 coordinate system, the central meridian is 114°, and the elevation adopts the 1985 national elevation datum.

 Project scope:

The coverage is about 9.75 square kilometers, and the effective mapping range is 7 square kilometers

 Project requirements:

It is necessary to provide 1:1000 scale digital line drawing results, and the accuracy is controlled within the error of 0.35 meters in the plane position and 0.28 meters in the elevation.

Project duration:

2016.3.13--2016.3.25

The specific production process flow chart of the project is as follows:

Project technical scheme:

1、 Camera calibration

Camera calibration is mainly to obtain accurate internal orientation elements and distortion parameters.

This solution adopts EasyCalibrate (ECT) on-site camera calibration software, which has low cost, convenient operation and reliable results.

In fact, a camera calibration has been done the day before the flight.

Calibration report (the results of the calibration are common to domestic and foreign aerial survey software)

2、Route design of survey area

The schematic diagram of the standard scheme of route planning and image control point layout in this scheme is shown in the figure below:

The heading overlap is 75%, and the side overlap is 50%.

The ground resolution is about 7cm, and there are 13 regular routes.

The relative flight altitude is about 380 meters, and there are 2 structured routes.

The relative flight altitude is about 420 meters (10% higher than regular routes).

3、Layout and measurement of image control points

This scheme uses a new type of drone control scheme:

Four control points are selected at the four corners of the survey area, and each point is arranged in a double-point manner, a total of 8 points (actually only 4 image control points are used, and the other 4 are used as spare points-to prevent high-rise buildings from blocking Part of the image control points, so the double-point method is used), which are respectively arranged at the corner points of the framework route (the two outermost regular routes intersect with the framework route, as shown in the above schematic diagram). 15 check points are evenly measured in the middle.

4、 Aerial photography by drone

The UV16 fixed-wing electric UAV customized by Visiontek is used this time. The ceiling of the UAV is 3800 meters, the endurance time is 150 minutes, and the effective aerial photography time can reach 120 minutes (300 meters relative altitude). It is aimed at Nikon. D810 and Canon 5D3, 5DS and 5DSR have specially customized dual-axis gimbal (the camera is mounted on the dual-axis gimbal on the left below, and the gimbal weighs about 1kg). This time, the 5D3 camera is used, plus dual-frequency differential GPS (such as The yellow and white shown in the lower right picture are differential GPS and antenna respectively, with a total weight of about 500g).

5、OKMatrix flight quality inspection

OKMatrix provides users with the ability to quickly inspect the quality of the field.It can effectively check the overlapping degree of aerial photos, rotation angle, course curvature, aerial photography loopholes and so on.After the aerial shooting, the flight quality inspection was done on the spot with a laptop computer. The inspection results are as follows:

Display of DOM superimposed DEM results calculated by one-click quick puzzle solving

Overlap check chart

It can be seen from the above figure that the flight quality is very good, and the mapping route ensures that the overlap is above 3 degrees.

6、HAT aerial triangulation

This program adopts HAT1.0 aerial triangle encryption software and PATB for aerial triangle encryption. HAT has the characteristics of automatic point transfer, automatic construction, automatic flight belt division and image sorting.

In the entire aerial triangle encryption process, only 4 image control points are used, 9 points in the middle are used as check points (the red point is not penetrated), and a total of 13 points are penetrated (shown in yellow in the figure below)

The final adjustment result is shown in the figure below:

The residuals in the above figure are in order: point name dX dY dZ dXY. From the checkpoint results, the accuracy of aerial triangle encryption fully meets the requirements of 1:1000 basic surveying and mapping accuracy.

After meeting the aerial triangulation accuracy requirements, export the MapMatrix project file, and further check the aerial triangulation encryption accuracy in the stereo mapping:

5、1:1000 digital line drawing production

This solution uses the MapMatrix stereo mapping module FeatureOne, which can realize the integration of stereo collection, editing, and storage. The final digital line drawing results can also be exported to various data formats such as DWG and MDB.