JPS5847059B2 - Image file creation device - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an image file creation device, and in particular, it converts MSS images obtained by scanning the earth's surface using a multispectral scanner (hereinafter referred to as MSS) mounted on a satellite into a topographic map. The present invention relates to an image file creation device suitable for creating a file as image data having a predetermined area size.

Although there is active research on creating topographic maps and analyzing crop distribution on the ground using MSS images, these remain experimental studies.

A major reason for this is that one screen of images is
In the case of the DSAT satellite, it is large at 3240 x 234 Q pixels,
Image processing requires an extremely large storage capacity, the correspondence between MSS images and topographic maps must always be considered, and MSS images have geometric distortions due to the attitude of the satellite, etc. There are many things that can be mentioned.

In particular, it has been reported that in order to correct the geometric distortion of an entire screen of this MSS image, it is possible to perform correction with a predetermined required accuracy by using a polynomial of order 3 or higher (RoB
ernste in: “Digital Image
Processing for Earth 0bse
rvation 5ensor Data"IBM J
, Res Develop Jan, 1976).

However, as mentioned above, the number of pixels on one screen is large, and even if a large general-purpose computer is used, the calculation time required for this correction is about one hour.

Considering these circumstances, it is possible to handle MSS images by correcting their geometric distortion and creating a file of partial images with a size corresponding to the topographic map, rather than preparing the MSS images as files as they are. becomes extremely easy.

Hereinafter, this will be referred to as a satellite map file.

An object of the present invention is to provide an image file creation device for creating a satellite map file.

As mentioned above, the MSS image and the latitude and longitude have a correspondence relationship using a polynomial of degree 3 or higher, and geometric distortion can be corrected with an error within one pixel in the case of LANDSAT.

On the other hand, topographic maps are created based on longitude and latitude, and one 1:50,000 topographic map published by the Geospatial Information Authority of Japan has 15 minutes of longitude and 10 minutes of latitude.

Therefore, the correspondence between the latitude and longitude of the four corner points of the topographic map is ℃
It can be converted into the number of pixels of a plane image, and an image including the four corner points can be extracted with high accuracy.

Since 1:50,000 topographic maps are produced using the Transverse Mercator (UTM) projection method, satellite images are
Affine transformation coefficients are determined so that the quadrilateral formed by the pixels at the four corner points resembles the topographic map by correcting geometric distortion using ne transformation.

The address of the image is calculated using this coefficient, and the address of the output image is calculated at high speed using pipeline control using the address of the input image. A similar geometric distortion corrected image is obtained.

This process can be easily systemized and a satellite map file can be created in which the entire screen of the satellite image is divided into regions corresponding to topographic maps.

The present invention will be described in detail below using a LANDSAT image as an example.

Using a third-order polynomial, the pixels of the LANDSAT image correspond to the latitude and latitude within one pixel.

LANDSAT pixels (■, J) from latitude and latitude (θ, λ)
The functions to are expressed as f and g.

To create a geometric distortion corrected image for any topographic map, first calculate the latitude and latitude of the four corner points of the topographic map by ((θ(
k), λ(k)): = 1.2, 4), extract 512 x 512 pixels from the LANDSAT image and store them in the image memory.

If the coordinates of this image memory are expressed as (I'(k), J'(k)), then the pixels of LANDSAT (I(k), J(k))
) is converted by .

(1-; I', !512.1≦J'≦512) A 1:50,000 topographic map is created using the U, T, M, and projection methods, and the length of latitude and longitude is exactly 50,000 minutes. It is entered in 1.

Therefore, in order to obtain an image similar to a topographic map, it is converted into a quadrilateral with a length ratio of 15 minutes longitude and 10 minutes latitude.

At 36°N, it is calculated as 36.98 cIrL x 45.08 on a 1:50,000 topographic map with a length of 18.49 k weave and 22.54 km.

On the other hand, the corrected image is created in the image memory and has a maximum of 512X
If the long side (horizontal) is 512 pixels, then the vertical side is 420 pixels.
Becomes a pixel.

Also, the center point of the topographic map is (256, 5, 210, 5) of the image.
corresponds to

Coordinate values of input image memory ((I'(k), J'(k)
: k = 1.2, ......, 4) and, if necessary, add the coordinates of the center point, etc. to obtain the position information before conversion and the corresponding output image memory coordinates ((ID(k), JD (k)):
= 1.2, . . . , 4), and if necessary, add the corresponding coordinate values of the center point, etc., and use the least squares method to determine the coefficients of the Affine transformation as position information after the transformation.

Output coordinate values (ID, JD
) can be concretely written as determining the coefficients (a, bl c) and (d, e, f).

This coefficient is determined from at least three sets of (I/, J', ID, JD), but in order to reduce errors, a set of 3 and 0 is used.

Therefore, if M sets of (I/, J', ID, JD) are given, then ((Xklykluklvk)2 -1,
2. (If formula B1 is also calculated, Affin
Coefficient power of e transformation: Find A = (u, v, 1) and At
-A is a 3×3 matrix and can be easily solved algebraically.

As for (a, b, c), representative display can be obtained.

Here det(At-A) and 11 represent determinants.

(d, e, f) are also found in exactly the same way. Addition, multiplication, and division are necessary to calculate these.

Using the A f f ine conversion coefficients (a, b, c) and (e, f, g) thus determined, coordinate calculation is performed using equation (A).

If the output image is 512X420, 1jIDf5121
-4JD-<420 and (ID, JD) = (1, ■), (
2, 1), ...... (512, 420), and use formula (4) to calculate the coordinate value (I/(1, 1) of the input image memory
), J' (1, 1)) (J' (2, ■), Jl (2, ■
))...(I'(512,420), J'(5
12,420)) is determined and the density value of that image is outputted to image memory address (1,1), (2,1),...(5
12, 42o), an Affine-converted image is created on the output image memory.

In this case, the calculation result of the equation is generally not an integer value, but the shortest distance method or the like can be used to select the density value of the memory address of the nearest integer value.

As a result, the calculation of equation (4) can be performed at high speed, and if an image memory is used that can randomly access the input image, a geometric distortion corrected image can be obtained extremely quickly.

The above was performed on a topographic map whose corresponding area is included in any LANDSAT image, but by performing this operation on all included topographic maps, an image file with geometric distortion corrected for each topographic map corresponding area can be created. can.

FIG. 1 is a block diagram showing one embodiment of the present invention.

1 is latitude and longitude data), and here the latitude and longitude data (θ, λ) of the four corners of a large number of topographic maps of 1/50,000 are held, respectively.

2 is a satellite image file, some LANDSAT
The MSS image fla is included.

The MSS image also includes additional information indicating which part of the earth the image is from.

3 is a control unit for cutting out the MSS image 0 partial image.

The cut out partial images are stored in the partial image memory 4.

The control section 3 operates according to the flowchart shown in FIG.

First, in the flock 31, the latitude and latitude data ((θ(k), λ(k)), k
=1.2.3°4).

Next, in block 32, M corresponding to these latitude and longitude data
Pixel position on SS image ((I(k), J(k)), (k
-1,2,3,4)).

In the flock 32, using the functions f and g of latitude and longitude and pixel position obtained by the method shown in the above-mentioned document,
Calculation is performed according to equation (1) above.

In block 33, (2
) The central (average) pixel position (■, J) is determined according to the formula.

Finally, in block 34, data of a partial image of 512×512 pixels is cut out with this pixel position (T, end) as the center and is supplied to the partial image memory 4.

Since the pixel position in the partial image memory 4 is represented by (■', Jl), it has the relationship of equation G3), so in the block 35, the pixel position ((I '(k), Jl(k)), k = 1.
2°3.4) and supplies it to the coefficient calculating section 5.

The coefficient calculation unit 5 calculates coefficients a, b, e, d, e, f of Affine transformation for correcting the geometric distortion of the partial image stored in the partial image memory 4 according to the formula (0).

The determined coefficients are supplied to the address calculation section 6.

The address calculation section 6 calculates the pixel position (address) of the pixel data to be read from the partial image memory 4, and also generates the address of the output image memory I that accommodates the read pixel data.

When the address of the output image memory 7 is expressed as (ID, JD), the relationship is expressed by equation (A).

That is, the address calculation unit 6, as shown in FIG.
ID counter 61. A JD counter 62 is provided, the output of which is supplied to the output image memory 7 as well as an I/calculation circuit 63 and a J signal calculation circuit 64.

These calculation circuits 63 and 64 supply addresses (l, Jl) calculated according to equation (A) to the partial image memory 6.

Note that the calculation units 63 and 64 are based on Japanese Patent Application No. 5233315.
It is preferable to use the circuit described in Japanese Patent Publication No. 58-6977.

For example, in the case of the 1:50,000 scale topographic map 1 Yokohama included in the July 29, 1976 image of the Kanto region by LANDSAT-H, the four corners in the image memory are The input image coordinates of the point ((I'(k),
J'(k)) = 1.2, 4) and the output image ((I D(k), JD(k)): k = 1.2,
...4) is.

Affine transform coefficients (a, b, c) and (d, e,
f) is calculated according to the formula (0), a=o, 15401
2 b=o, 182816c=22.763173
d=-0,104207e=0.545465
f=149.983742.

This coefficient and the information (ID, JD) are input to the address calculation unit 6, and the address (1', JD) of the partial image is inputted according to formula (A).
/) is calculated.

Since (■', J/) is generally not an integer, it is converted into an integer by interpolation using the shortest distance method, which calculates the point at the shortest distance by rounding off the fractions below the decimal point and using it as a memory address.

Referring again to FIG. 1, the corrected partial image obtained in the output image memory 7 is supplied to the file creation unit 8 together with the latitude and latitude data in the latitude and latitude file 1.

The file creation unit 8 associates the corrected partial images with the latitude and latitude data and classifies and stores them in the satellite map file 9.

Thereafter, satellite map files corresponding to different latitude and longitude data are created in the same manner.

FIG. 4 shows a system for utilizing the satellite map file 9 obtained by the device according to the invention.

For example, the topographic map instruction unit 10 generates a 1/50,000 scale topographic map.
When the controller 11 instructs "Yokohama", the control unit 11 outputs latitude and longitude data representative of this topographic map to the satellite map file 9.

The file 9 outputs image data corresponding to the latitude and latitude data to the control section 11 and is displayed on the display section 12.

Therefore, the user can easily obtain any partial image of the MSS image, and this partial image has geometric distortions corrected and matches the topographic map, making map creation etc. extremely easy. .

As described above, according to the present invention, it is possible to easily create a satellite map file that is easy to use.

For example, 0.25 seconds is sufficient to correct the geometric distortion of the partial image in the partial image memory 470 and obtain the output image, and one screen of LANDSAT is generally 1/50,000 of this time.
This method includes several dozen partial images corresponding to a topographic map, and can be processed more than 100 times faster than the conventional method of correcting geometric distortion using a general-purpose large-scale computer.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of this invention, FIGS. 2 and 3 are diagrams for explaining an embodiment of this invention, and FIG. 4 is a diagram showing a system using an embodiment of this invention. FIG. 1... Latitude and latitude table, 2... Satellite image file, 3... Control unit, 4... Partial image memory, 5... Coefficient calculation section, 6...
・-address calculation unit, 7...output image memory,
8...File creation department, 9.1°°°Satellite earth satellite child ile.

Claims (1)

[Claims] 1. A satellite image file containing a large number of satellite images obtained by scanning the earth's surface with a scanner mounted on a satellite, a latitude and latitude table containing latitude and longitude data representative of a given topographic map, and this latitude and longitude table. means for reading out the latitude and latitude data from and calculating pixel positions on the satellite image corresponding to these latitude and latitude; a partial image memory that reads out and stores satellite image files; means for calculating coefficients of affine transformation for converting the partial image into an image similar to the topographic map; an address calculation circuit that calculates the pixel position to be read from the partial image memory;
It includes an output image memory that sequentially stores data of pixels designated by this address calculation circuit, and a satellite map file that stores the contents of this output image memory in correspondence with the corresponding latitude and latitude data of the latitude and latitude table. An image file creation device characterized by: