Making orthophoto map of satellite remote sensing data

Making of Satellite Remote Sensing Data 1 Orthophoto Map

With the rapid development of satellite remote sensing technology, the mapping accuracy of image maps is getting higher and higher.

Satellite remote sensing technology combines modern information technology and intelligent remote sensing information processing technology, which provides technical support for urban planning and understanding of regional environment.

Orthophoto map is made by using DEM to carry out differential correction, radiation correction and mosaic on satellite remote sensing images, and cutting image data according to regulations.

Keywords satellite remote sensing image map making

With the rapid development of science and technology, human society has entered the digital information age.

Digital information plays an important role in promoting China's national economic and social development.

The traditional production process of digital orthophoto mainly includes DEM generation and digital orthophoto generation, indoor triangulation, field control point measurement, aerial photography and so on. In the process of digital image processing, it is characterized by long time consuming, high cost and low precision [1].

Therefore, the traditional topographic map can no longer meet the needs of the rapidly developing modern society.

Digital orthophoto map is rich in information, intuitive and accurate, and widely used in land dynamic monitoring, road design, farmland water conservancy construction, flood control and disaster relief and other fields. With the rapid development of science and technology, high-precision orthophotomap is of great significance to our country.

1 development status of digital orthophoto map

In recent years, computer technology and digital orthophoto map production technology have developed rapidly, and digital orthophoto map plays an important role in urban planning, construction and management.

Digital orthophotomap has been widely recognized by urban planning experts, and its application in practice has been further developed.

At present, most cities use digital orthophoto maps when obtaining basic information and updating image databases.

Since the 1960s, the term remote sensing has been widely concerned by the society.

Remote sensing refers to detecting distant targets and analyzing the obtained information, so as to determine the unique attributes of the targets and the relationship between the targets [2].

Satellite remote sensing image refers to obtaining the objective reality of the earth's surface by using modern satellite remote sensing technology, and analyzing the data of this object, and then making an image map, which finally serves the practical application.

At present, governments and people of insight around the world have reached an agreement? Digital earth? * * * knowledge, they are all striving for the strategic commanding heights of the information age.

In this context, will China? Digital China? Put it on the agenda, and then? Digital city? what's up Digital China? It plays an important role in the economic development of China.

What is remote sensing information? Digital city? The accuracy of orthophoto map is related to the development process of digital cities in China.

With the rapid development of remote sensing information technology, people are more and more aware of the inherent laws of remote sensing information, which has been widely used in many fields of cities.

Digital orthophotomap plays a very important role in planning urban construction, improving urban environment and improving social and economic benefits.

Urban landscape model is the embodiment of the present situation of the city and plays an important role in urban planning.

The traditional urban landscape model can't show the real situation of the city. Using digital orthophoto map to build a three-dimensional landscape model of digital city not only improves the accuracy, but also can browse the urban landscape from multiple angles, providing decision-making basis for urban construction and national economic development.

At present, the technology of constructing digital landscape model using remote sensing information is becoming more and more mature. Using satellite remote sensing data to collect the plane information of the city, and using the existing digital elevation model data, we can make high-precision digital orthophoto maps.

2. Main technical difficulties in making digital orthophoto map.

2. 1 The camera image splicing gap is obvious.

At present, there is a great gray contrast between stereo image pairs. If the mosaic lines in overlapping areas are not handled properly, people will find several obvious contrast gaps in a picture, which will lead to visual disconnection.

Therefore, in order to ensure the image quality and improve the mosaic effect of the image map, the operator should splice the contrast lines in areas with small projection differences, try to choose areas close to streets, rivers, highways and so on, and prohibit the use of buildings that divide the whole from one line.

When stitching images, operators should adopt feathering method to avoid hard streets.

After the image stitching is completed, the operator should start framing the image and deal with clutter again.

2.2 The building is severely deformed.

When correcting the digital orthophoto map, the average elevation is mostly used to construct the ground figure, and the average elevation plane is used to highlight the building.

Because of the great difference in the projection of buildings with different elevations, the digital orthophoto map is prone to deformation.

When collecting significant building data, the operator should collect significant buildings and non-significant buildings respectively, and ensure that their characteristic lines do not intersect.

When deleting the characteristic line data of non-prominent buildings, the operator should calculate the characteristic line data of prominent buildings and generate DEM. Only by correcting the image in this way can the building not be deformed. When deleting the data highlighting the building characteristic line, the operator should keep the data of its characteristic line and calculate and generate DEM.

2.3 Orthophoto image with uneven color.

In the process of taking images by satellite remote sensing, some are bright in the middle and dark around, while others are bright on the top and dark on the bottom. Therefore, if the operator does not properly handle the pictures taken during shooting, the DOM color produced in the later period will be distorted and uneven, which will seriously affect the judgment of image data.

At present, most operators use DUX aerial survey image processing software of Chinese Academy of Sciences when processing principle images.

DUX aerial image processing software is used to homogenize the color of the original image.

There are two main types of uniform light processing parameters: one is to determine the effective range and scene processing coefficient; The second is to adjust the brightness, color and sensitivity parameters of the image.

The specific steps are as follows: firstly, the original image is homogenized; Then, open the relevant image data in batches, and perform uniform light processing in batches. When performing uniform color processing, the operator should adjust the front and rear images of each flight zone and adopt? Adaptability? Make adjustments; Finally, according to the first and last adjusted red image, the intermediate image is automatically matched, and the images generated by uniform color are processed in batches.

3 the principle of making digital orthophoto map

Digital orthophoto map (DOM for short) is the image data generated by scanning digital aerial photos or remote sensing images (monochrome or color) pixel by pixel with DEM, radiation correction, differential correction and mosaic, and cutting them according to the specified map range. It is a plan with kilometer grid, outline (inside and outside) decoration and labeling [3].

Digital orthophoto map is different from the map we usually see. It is the true reflection of our ground information on the image map. It is not only undistorted, but also richer and more readable than ordinary maps.

Digital orthophotomap can be used as background information, from which necessary natural resources and social information can be extracted, providing a lot of necessary basis for preventing natural disasters and planning public facilities.

The principle of making digital orthophoto map is: according to the characteristics of orthophoto map, after applying professional geographic information remote sensing software to correct the radiation and geometry of the original image map, all kinds of deformities and displacement errors are eliminated, so as to obtain more accurate digital orthophoto map under fine geographical conditions and various satellite remote sensing.

At present, the digital photogrammetry used at home and abroad mainly includes: Jx-4A full digital photogrammetry system, which is a measurement system developed by Siwei Beijing Company in China; ImageS-station workstation；, a measuring system developed by Intergraph Company of the United States; VituoZo system, which is a system developed by Wuhan Shipu Company.

These measuring systems can make orthophoto maps of various scales, and the principle of making them is the same, all of which are differential correction of numbers [4].

The principle of making digital orthophoto map is as follows: firstly, a stereo image pair is formed according to the image texture, and then a digital elevation model is generated; Then, the matched pixels are corrected by digital differentiation, and an orthogonal image is generated [5].

This drawing method can not only ensure the image quality, but also prolong the drawing cycle of equipment, which requires high comprehensive quality of operators.

Therefore, when using digital orthophoto map for drawing, operators should have a deep understanding of all-digital photogrammetry system, improve their knowledge of computer graphics and image processing, and constantly improve their working ability.

4. Making remote sensing orthophoto map

4. 1 Collect the original satellite image.

In recent years, with the continuous development of remote sensing technology, remote sensing satellite images emerge one after another.

When making maps by remote sensing, Ikonos, World View and QuickBird are mainly used as the original satellite image data.

These image data have the advantages of large file data, high ground resolution and easy management, so they are widely used to make high-precision orthophoto maps.

4.2 Image Correction, Registration and Fusion

First, use GPS control points to correct the image.

When using satellite remote sensing data to make orthophoto map, the operator starts to control the image after collecting the first batch of satellite image data, and uses GPS to control the image.

The essence of image map correction is to use the central projection to carry out orthorectification on the image data source to form orthorectification [6].

Operators can use the existing 1: 500, 1: 2000 and 1: 5000 to correct topographic map data, which can save costs and shorten the construction period to a certain extent, thus improving work efficiency and ensuring image accuracy.

Second, after completing the image correction, the operator should register the multi-spectral images.

The purpose of image registration is to identify pixels with the same name between two or more images.

Among them, the methods of image registration are: gray registration; Feature registration.

Thirdly, after image registration, the operator should fuse remote sensing images with different resolutions and ensure that the fused remote sensing images have good spatial resolution and multi-spectral characteristics, so as to enhance the images.

In the process of image resolution fusion, the operator needs to register the first two images and choose the appropriate fusion method during the processing.

Only when images with different spatial resolutions are accurately registered can the operator get satisfactory fusion results.

Fourthly, when supporting the remote sensing orthophoto map, the operator should choose the fusion system Cyberland which meets the remote sensing image registration standard to correct, register and fuse the image map.

At present, the widely used image mapping software includes QcickBird panchromatic image and QcickBird multispectral image.

4.3 Seamless splicing of image maps

Image stitching refers to the digital processing of geometric stitching, de-overlapping, color adjustment, etc. of several adjacent remote sensing digital images, and then stitching them into a complete new image map.

In the application of remote sensing images, there may be a big gap at the junction of multiple images, and multiple images are needed to cover this gap. Therefore, they need to study the image registration in this area and embed these images with strength in order to better process, analyze and study them.

The image mosaic process is as follows:

Firstly, the overlapping areas of images are determined.

The overlapping area of adjacent images is the implementation place of remote sensing image mosaic and the benchmark of other work.

For example, the adjustment of image tone, geometric stitching of images and the removal of image overlapping areas are all based on image mapping overlapping areas.

Therefore, the determination of overlapping areas between image maps is directly related to the mosaic effect of image maps.

Second, adjust the image tone.

Tone adjustment of image map is an important part of remote sensing image mosaic.

Because there are different phases and imaging conditions in the images, the radiation degree and brightness of the images to be stitched are different, so it is necessary to adjust the color tone of the images.

If the image has no hue, even if the geometric position of the image is well registered, the embedded image can not be applied to practical work.

Tone adjustment is an important part of image rendering.

Although the imaging phase of some remote sensing images is close to the imaging conditions, the random error of satellite remote sensing sensors will lead to inconsistent image tones, which will affect the practical application effect of image images, so it is necessary to adjust the color tones of satellite remote sensing images.

Third, image mosaic.

After determining the overlapping area and adjusting the tone, the operator can stitch adjacent images.

Image stitching refers to finding the seam line of the overlapping area of adjacent image maps that need to be stitched.

Therefore, the quality of seam lines in overlapping areas is directly related to the stitching effect of images.

In the process of stitching, even if the operator adjusts the tone of the image, the tone at the seam of the image will be inconsistent. Therefore, the operator needs to smooth the tone of the overlapping area of the image to improve the brightness of the mosaic, so as to ensure the seamless existence of the image mosaic.

Fourthly, in the process of stitching images, the operator should adopt a professional image processing system.

ImageXuite is a professional image processing system, which has powerful image smoothing and stitching functions.

The operator generates a seamless mosaic image through uniform light and uniform color and tone adjustment.

ImageXuite is an important image mosaic software. In most cases, it has a remarkable light-homogenizing effect and realizes better seamless image stitching.

However, there are some defects in image snow software, for example, the color matching function of images is not strong, and the processing effect of image snow is not good, when all homogenized images are dark. That is, the operator needs to use Photoshop software to adjust the image until it is better, then take the adjusted image as the main image, and finally homogenize other images. Through these procedures, the operator can get better images.

5 conclusion

With the rapid development of science and technology, satellite remote sensing technology has made great progress, and its image mapping accuracy is getting higher and higher.

At present, human society has entered the era of digital information, and digital information plays an important role in promoting China's national economic and social development.

Satellite remote sensing technology combines modern information technology and intelligent remote sensing information processing technology, which provides technical support for urban planning and understanding of regional environment.

Orthophoto is to use DEM to carry out differential correction, radiation correction and mosaic on the scanned satellite remote sensing image, and cut out the image data according to regulations, thus forming an image.

Digital orthophoto map is rich in information, intuitive and accurate, and widely used in land dynamic monitoring, road design, farmland water conservancy construction, flood control and disaster relief and other fields. With the rapid development of science and technology, high-precision orthophotomap is of great significance to our country.

References:

[1] Kong Juan, money,. Analysis on the improvement of the production quality of digital orthophoto map [J]. Journal of xuchang university, 20 12, (5): 120.

Li Haiyang, Wang Liying. Making orthophoto map of remote sensing based on PCI [J]. Mine Survey, 2009, (4): 44.

Zhang Yufang, Ouyang Ping, Cheng Xinwen, Cai Chong. Method of making orthophoto map based on lidar data [J]. Bulletin of Surveying and Mapping, 2008, (8): 44.

[4] Jomally, Zhang Lixia and Gong Wei. Study on the method of making orthophoto map and its application [J]. Surveying and Mapping and Spatial Geographic Information, 2009, (5): 150.

Liu Lihong and Wu Haikuan. Research on DEM Extraction and Orthophoto Map Making Based on Stereo Image Pairs [J]. Inner Mongolia Science and Technology and Economy, 201,(7):1kloc-0/.

Making orthophoto map of satellite remote sensing data II

Satellite remote sensing is a technology that uses aviation technology to launch artificial satellites into outer space of the earth to comprehensively observe celestial bodies on the earth's ground, above-ground space and outer space.

The data obtained from satellite remote sensing are widely used to make orthophoto maps. This paper expounds the sources and characteristics of satellite remote sensing data and satellite influence map, analyzes the methods and principles of error correction, registration and final unified fusion in the process of making orthophoto map, and briefly introduces the methods and processes of data information processing such as configuration, color matching and de-overlapping of orthophoto map.

Satellite remote sensing technology; Data; Information; Orthographic projection image; manufacture

introduce

With the advent of the information technology era in 2 1 century, satellite remote sensing technology is constantly being updated and improved.

At present, satellite remote sensing technology has achieved remarkable results in making orthophoto maps, and the mapping accuracy is getting higher and higher, far exceeding the accuracy of scale topographic maps.

Satellite remote sensing technology plays a powerful supporting role in urban construction, urban planning and understanding of environmental conditions and resources.

The urban image map made by satellite remote sensing technology has the advantages of small target recognition difficulty, clear content, large scale and easy interpretation. This technology has been widely used in all levels of social production and development.

This technology also helps to manage the ecological environment, collect professional information, monitor engineering projects and prevent various natural disasters.

1. Popular satellite image acquisition methods at home and abroad

With the deepening of the new scientific and technological revolution, satellite remote sensing technology is changing with each passing day. At present, the earliest satellite remote sensing technology in the world is the QuickBird satellite image from the data warehouse of the American Earth observation satellite. The ground panchromatic resolution of the satellite image reaches 0.6 1m, and the imaging range reaches 16.5? 16.5/km2, and then the United States successively launched space imaging Ikonos and Land sat TM satellite remote sensing images, which improved the image effect and imaging range compared with the QuickBird of earth observation.

Russia has produced a Spin-2 satellite image, the ground resolution is not as good as that of Land sat TM satellite remote sensing in the United States, but the imaging range can reach 200? 300/km2 has obvious advantages over three American satellites.

2. Error correction, registration and unified fusion of satellite images.

2. 1 digital error correction

Optical error corrector is a tool for converting aerial simulated photos into plane pictures, which is mainly suitable for digital images of traditional frame-mode aerial photos [1].

At present, there are many new satellite digital remote sensing technologies, and the influence data of these technologies can not be well converted by traditional optical error correction instruments.

Therefore, digital differential error correction technology was born.

This is a method to convert the digital image of aerial photography pictures into orthographic images by setting appropriate conceptual formulas and controlling the range and control points according to appropriate mathematical models through the effective parameters of the ground and the basic prototype of digital ground.

This technology is not only simple and convenient, but also widely used, and has become a widely used digital error correction technology at home and abroad.

2.2 Image Error Correction

In the process of image error correction, we must first clarify two points:

First, the GPS control point is the joint point of image error correction.

Secondly, adopting the corresponding scale error correction is the follow-up work to improve the image error correction.

When using remote sensing satellite data to make orthophoto map, the general shape and structure of the image are stabilized by using the control points in all directions of GPS, and then the image control screen is manually fine-tuned.

Finally, according to different scale standards (generally taking 1: 5000, 1: 2000, 1: 500 as reference standards), the topographic map data with complete image sheets are finally corrected [2].

After these two key points are made clear, the orthophoto map will be more true and accurate.

2.3 Registration of Multispectral Images

In other words, two or more images are compared and matched to find out the differences and supplement the final image data.

The registration of multispectral images is generally based on features and gray levels.

2.4 image unity and integration

Image unification and fusion refers to the unification and fusion of satellite remote sensing data with different resolutions. The unified and fused image data has higher spatial resolution, easier target recognition and multi-spectral effect, which makes people vivid at first glance [3].

The key of this operation lies in the error correction of image data and the registration of multi-spectral images. Only when these two steps are completed, the unified image fusion effect will be better.

3. Configuration of satellite images

The production of orthophoto map of satellite image is an extremely complicated and extensive work, which mainly includes the collection of satellite remote sensing image data in the early stage, the error correction of digital and image data, the registration of multi-spectral images, the unification and fusion of influence, and the adjustment and embedding of overlapping areas, tones and images in the late stage of image production [4].

Image adjustment and embedding need to integrate a large number of image data with different resolutions, shapes, research areas and boundaries, and then carry out error correction, registration and final image mosaic.

Therefore, there are three steps to make a digital image mosaic with good effect and balanced proportion.

First, determine the overlapping area.

In the process of making orthophoto map of satellite image, it is very common to face a large number of pictures, such as overlapping research areas, overlapping seams or overlapping graphics.

But how to find these overlapping areas and mark them in the graphic data, which is beneficial to the later image mosaic? Here we must pay attention to the following two aspects: first, find the overlapping area of adjacent images; Secondly, after the overlapping areas are determined, they should be marked with different markers.

Second, adjust the color tone.

Tone adjustment is an important link in making orthophoto map. There are many differences in images with different resolutions, different imaging conditions or pictures. Because of the complete effect of satellite orthophoto, if the mosaic image is different and the radiation level is different, the difference of sensitivity and brightness of the image will change seriously because of the final quality of the image, and it will not be a balanced satellite orthophoto.

Therefore, we should pay attention to the adjustment of image color and tone in this link.

Therefore, when adjusting colors and tones, we should look for images with similar colors and small differences in tones, while images with large differences in colors should be adjusted by special methods to achieve the overall effect.

Finally, the image is embedded.

After confirming the overlapping area and adjusting the tone, it is the final image embedding work.

In this link, it must be noted that images with similar colors and adjacent positions should be found for embedding, and a connecting suture line should be confirmed in the two images to be embedded when embedding.

The quality of this connection suture is closely related to the embedding effect of the final image, so the selection of connection suture must be foolproof.

During the embedding process, two embedded images may have different tones at the joint. At this time, the tone of the two images must be finally adjusted by the method of brightness infiltration until the visual sense is harmonious, so that the defects at the joint can not be detected at a glance.

4. Concluding remarks

The production of orthophoto map of satellite image is an extremely complicated and extensive work, which mainly includes the collection of satellite remote sensing image data in the early stage, the error correction of digital and image data, the registration of multi-spectral images, the unification and fusion of influence, and the adjustment and embedding of overlapping areas, tones and images in the later stage of image production.

When making orthophoto map with satellite remote sensing data, the boring remote sensing image operation software Cyberland is generally used for three operations: error correction of digital and image data, multi-spectral image registration and unified fusion of influence, and the professional image processing system ImageXuite is generally used for three operations: overlapping area, hue and image adjustment and embedding in the later stage of image production.

refer to

[1] Wang Rui Lin Yuechun. On the skills and experience of making digital orthophoto map [J]. Surveying and Mapping and Spatial Geographic Information, 201(34):110.

Liu Peng, Huang Guoqing, Che Feng. On the production of high-quality digital orthophoto map [J]. Urban Survey, 20 12 (5): 80.

[3] Answer the stars. Research on fast mapping method of digital orthophoto based on OrthoVista [J]. Bulletin of Surveying and Mapping, 201(8): 54-56.