Orthographic image and true orthophoto image

Usually listen to satellite photos/satellite photos/aerial photography. Let's take a look at the development of remote sensing. Here, we borrow the words from China Science and Technology Fair directly.

Original address:/space/ygyszdq/radi _ ygzl/201506/t 20150609 _130/kloc-0.html.

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Remote sensing originated from aerial photography in the19th century and was mainly used for aerial reconnaissance. With the development of platform technology, it has gradually entered the stage of aerial remote sensing. Modern remote sensing is a new technology based on aerial photography developed in the early 1960s. Started for aerial remote sensing, since 1972, the United States launched the first land satellite, marking the beginning of the era of space remote sensing. After decades of rapid development, it has become a practical and advanced space exploration technology.

The following are milestones in the development of remote sensing:

1800: The infrared band was discovered by Sir W Herschel.

1839: The photography exercise appeared.

1847: the infrared spectrum was discovered by J.B.L Foucault.

1859: Get the ground photos through the balloon platform.

1873: The theory of electromagnetic spectrum was discovered by J.C. Maxwell.

1903: the invention of aircraft

1909: Get the ground photos through the airplane platform.

1914-1918: during the first world war, the discipline system of aerial photogrammetry was gradually formed.

193 1- 1945: During World War II, electromagnetic waves other than visible light were widely used.

1957: The former Soviet Union launched the first artificial earth satellite.

1959: Get the first image of the Earth in space.

1960: the first TIROS meteorological satellite was launched.

1960: The world's first laser was born.

1962: the first environmental remote sensing conference was held, marking the beginning of remote sensing from photogrammetry.

1972: Landsat-1(erts-1) was successfully launched with MSS sensor.

1973: Skylab pioneered the application of radar altimeter by human beings.

1978: The successful launch of SEASAT marks a new era of space SAR observation.

1982: Landsat-4 was successfully launched with TM sensor.

1986: France launches the first commercial earth observation satellite SPOT.

1986: development and application of hyperspectral sensor AVRIS

1993: Germany successfully developed the first commercial airborne lidar system TopScan.

1993: The United States and Canada have successfully developed the airborne laser detection system SHOALS.

1999: NASA launches EOS series satellites, mainly equipped with MODIS sensors.

1999: IKONOS is launched into the era of commercial high-resolution satellites.

1999: China's first land resources satellite, China-Brazil Resources Satellite 0 1, was successfully launched.

2000: EO- 1 satellite launch, mainly equipped with ALI and HYPERION sensors.

2000: Successfully implemented the SRTM space shuttle interferometric radar mapping plan.

2002: Successfully launched the large-scale EU environmental satellite ENVISAT- 1.

2003: The first spaceborne laser altimeter, ICESat- 1/GLAS, was successfully launched.

2004: The world's first commercial airborne full-waveform lidar system was successfully developed.

2006: CALIPOSO, the world's first applied spaceborne lidar system, was successfully launched.

2007: German TanDEM-X satellite was successfully launched.

2009: ASTER GDEM, the most accurate DEM data in the world, was released.

2009: GOSAT, the world's first greenhouse gas satellite, was successfully launched.

20 13: The first 1 issue of China High Score Series was successfully launched.

20 13: Landsat-8, an American land resources satellite series, was successfully launched.

20 13: China's first spaceborne synthetic aperture radar satellite HJ- 1C was successfully launched.

20 14: eu sentinel series 1A was successfully launched.

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The above are almost the satellite pictures we see in various map websites or map apps every day.

It is a common phenomenon that almost all the houses we see on such a map are inclined. Here I put a screenshot of a certain area in Shanghai.

Think Google data is better? Then I also put a screenshot of Google data here. All the same.

Seeing this, friends who have done vectorization according to satellite photos before should be deeply touched, that is, the corner of the house, and the vectorized lines are all on the roof! ! ! ! !

Once upon a time, countless scholars tried to process satellite images into real projection images that could be vertically projected on the ground, with little effect. Here's a reference to the definition of a realistic image.

Original link: /s? wd = paper uri:(0374 BF 8 18 debf 29d 3d 50409 a3 F5 a 4773)& amp； filter = sc _ long _ sign & ampsc _ ks _ para = q % 3D % E4 % BC % A0 % E7 % BB % 9F % E6 % AD % A3 % E5 % B0 % 84% E5 % BD % b 1 % E5 % 83% 8F % E5 % 92% 8C % E7 % 9C % 9F % E6 % AD % A3 % E5 % B0 % 84% E5 % BD % b 1% E5 % 83% 8F & amp； TN = SE _ Baidu xueshu _ c 1g jeupa & amp； ie=utf-8。 sc _ us = 82 14084837435359424

Digital True Image (TDOM) is an image map formed by using digital surface model (DSM) and digital differential correction technology to correct the geometric distortion of the original image, and resampling the image in the whole survey area to correct the image angle to a vertical angle.

In a word, it probably means that the image is the result of the vertical projection of the building on the surface.

Today, has the real shooting been realized? The answer is yes.

At present, the main realization process is oblique photography, and the three-dimensional model of aerial photography results is obtained through three-dimensional calculation, and the texture of the three-dimensional model is projected vertically.

Look at some renderings. This is based on the aerial photography of unmanned aerial vehicles, generating advanced aerial 3D models and then generating real aerial images. At the same time, it is compared with satellite image data.

At present, there are many softwares that can realize this method. Basically, as long as the three-dimensional point cloud data is obtained before the orthographic image is output, the final image result can be considered as a real orthographic image.

There are several softwares mentioned here, such as Smart3D, Pixel4D and LocaSpaceViewer.

The above contents are based on the software I have come into contact with at work and my own experience in the company's software development process, and I have no attitude towards each software.

Welcome more discussion.