Automatic registration of images in digital terrain elevation data

• US 6,853,332 B1
• Filed: 04/24/2002
• Issued: 02/08/2005
• Est. Priority Date: 07/19/2001
• Status: Expired due to Fees

• Current Assignee: Atlantic Inertial Systems Incorporated (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: BAE Systems Plc
• Inventors: Brookes, Tom M
• Primary Examiner(s): Gregory, Bernarr E.
• Application Number:
  US10/137,489
• Time in Patent Office: 1,021 Days
• Field of Search: 701/200, 701/201, 701206-212, 701/223, 342/25, 342 61- 66, 342/175, 342/176, 342/179, 342/190, 342191-197, 342/118, 342/120, 342/121, 342/122, 34235701-35717, 342/25.R, 342/25.A, 342 25 B- 25 F, 382/100, 382/113, 382/154, 382/190, 382/191, 382/192, 382209-228, 382/276, 382/278, 382279-281
• US Class Current: 342/191
• CPC Class Codes: G01C 21/005 with correlation of navigation data from several sources, e.g. map or contour matching G01C21/30 takes precedence
• CPC Class Codes: G01C 5/005 altimeters for aircraft G01C5/02, G01C5/06 take precedence
• CPC Class Codes: G01S 13/882 for altimeters measuring height using barometric means G01C5/06
• CPC Class Codes: G01S 19/14 specially adapted for specific applications
• CPC Class Codes: G01S 3/7864 T.V. type tracking systems
• CPC Class Codes: G06T 17/05 Geographic models
• CPC Class Codes: G06T 7/30 Determination of transform parameters for the alignment of images, i.e. image registration

Abstract

A method of registering reconnaissance image data with map data is disclosed, comprising recording image data at a plurality of positions, together with the role, pitch and height above mean sea level data from an airborne navigation system and imaging system, and recording altitude of a reconnaissance craft from an altimeter; obtaining a difference between said recorded altitude data, and an altitude calculated from said navigation system data and a map data; selecting a difference data having a lowest standard deviation, and at a position of said selected difference data generating a three dimensional surface data using a bi-quadratic equation; generating a bi-quadratic surface of each of a plurality of positions for which data is recorded; generating a difference data between said bi-quadratic surface data, and height data obtained from said map, and minimising an error between bi-quadratic surface data and said height data by translating said position data relative to said map data, until minimum error is achieved; registering said image data with said map data after applying a said translation of said image data.

Claims

1. A method of matching reconnaissance image data with map data, said method comprising the steps:

recording a frame of said image data at each of a plurality of positions;

recording a position data at each of said positions;

recording an altitude above ground level data at each of said positions;

recording a height above mean sea level data at each of said positions;

for each said position, determining a first height above ground as a difference between said mean sea level, and a height data at said position read from said map data;

for each said position comparing said first height data with said altitude data to obtain a corresponding respective standard deviation of difference between said first and second heights;

selecting a position having a lowest standard deviation of a plurality of said standard deviations, and matching said image position to a corresponding position on said map for said position with said lowest standard deviation;

generating a surface data at said selected position;

comparing a height of said generated surface data with said map height data at said position, and obtaining a height error data between said generated surface height and said map height data; and

translating said image data until said error data is optimised.

2. The method as claimed in claim 1, wherein said step of translating said image data comprises translating said image data until a minimum overall error between said surface height data and said map height data is found.

3. The method as claimed in claim 1 or 2, wherein said step of obtaining a standard deviation of difference between said first and second height and said altitude data comprises:

for each said position, determining a difference between said first height data and said altitude data; and

;

determining a difference squared between said first height data and said is altitude data.

4. The method as claimed in claim 1, further comprising the step of:

recording roll and pitch data at said position;

using said roll and pitch data to determine a point of said image data which coincides with said position data.

5. The method as claimed in claim 1, wherein said step of generating a surface data at said position comprises:

generating a bi-quadratic surface data around said position.

6. A method for providing composite digital and terrain image map data, said method comprising the steps of:

(a) taking and recording a sequential series of terrain images from an airborne or above atmosphere vehicle having an internal navigation system, and an altimeter for taking and recording a sequential series of terrain images, navigation positions and altimeter readings;

(b) establishing and recording for each image the height of the vehicle above the terrain as indicated by the altimeter and the position, roll and pitch of the vehicle above the terrain as indicated by the navigation system;

(c) comparing the digital map terrain elevation data with the vehicle height data along the series of recorded terrain images;

(d) establishing and orientating matrices about selected data points along the series of recorded terrain images where the difference between the digital map terrain elevation data and vehicle height data is within a desired limit;

(e) calculating the differences and differences squared between the vehicle height above sea level and the digital map terrain elevation at each selected data point;

(f) repeating steps (a) to (e) for a further sequential series of terrain images;

(g) calculating a matching matrix from the data of step (e) for both series of terrain images to establish a standard deviation at each data point;

(h) identifying the smallest standard deviation which, when the vehicle position from the vehicle internal navigation system is correct, provides the centre point or centre point of the matching matrix; and

(i) estimating from the centre point, the difference between the digital map data and the vehicle navigation system data when the terrain images were taken from, from which the digital map and terrain images can be registered one with the other, to provide composite map data.

7. A method of registering reconnaissance image data with map data comprising the steps of:

recording image data from a plurality of positions, together with the roll, pitch and height above mean sea level data from an airborne navigation system and imaging system at those positions;

recording an altitude data of said positions, using an altimeter;

obtaining a difference between said recorded altitude data, and an altitude calculated from said navigation system data and a map data;

selecting a difference data having a lowest standard deviation, and at a position of said selected difference data generating a three dimensional surface data;

generating a three dimensional surface data of each of said plurality of positions for which said image data is recorded;

generating a difference data between said three dimensional surface data, and height data obtained from said map, and minimising an error between said three dimensional surface data and said height data by translating said position data relative to said map data, until minimum error is achieved;

registering said image data with said map data after applying said translation of said image data.

8. A method of matching a set of a plurality of reconnaissance image data frames collected by a reconnaissance vehicle traversing over a terrain, with a map data, said method comprising the steps of:

recording said plurality of reconnaissance image data frames using an imaging system on board said reconnaissance vehicle, as said vehicle flies over said terrain;

for each said reconnaissance image data recorded, recording a vehicle latitude, longitude position data using a navigation system on board said vehicle;

for each said longitude, latitude position data, recording a height above mean sea level data using said on board navigation system;

for each said position data, recording a height of said vehicle above said terrain, using an on board vehicle height measurement system;

matching each of said reconnaissance vehicle latitude, longitude positions, with corresponding X, Y positions of said map data; and

matching said image data with said map data.

9. The method as claimed in claim 8, wherein said step of matching said vehicle positions with said map data comprises:

(i) comparing digital map terrain elevation data with vehicle height data along the set of recorded reconnaissance image data frames;

(ii) establishing and orientating matrices about selected data points along the series of recorded reconnaissance image data frames where the difference between the digital map terrain elevation data and vehicle height data is within a predetermined limit;

(iii) calculating differences and differences squared between the vehicle height above sea level and said digital map terrain elevation at each said vehicle position data;

(iv) repeating steps (i) to (iii) for all data frames in said set of data frames;

(v) calculating a matching matrix from the data of step (iv) for both series of reconnaissance image data frames to establish a standard deviation at each vehicle position data;

(vi) identifying a smallest standard deviation which, when the vehicle position data from the vehicle navigation system is correct, provides a centre point of the matching matrix; and

(vii) estimating from said centre point, a difference between the map data and the vehicle position data where the reconnaissance image data frames were taken from, from which the digital map and reconnaissance image data can be registered one with the other, to provide composite map data in which said reconnaissance image data is registered with said map data.