Method for the stereophotogrammetric survey of large-dimension objects on sea and land

• US 4,641,960 A
• Filed: 05/31/1984
• Issued: 02/10/1987
• Est. Priority Date: 06/03/1983
• Status: Expired due to Fees

• Current Assignee: AGIP SpA (GALP - Petroleos e Gas de Portugal SGPS SA)
• Original Assignee: AGIP SpA (GALP - Petroleos e Gas de Portugal SGPS SA)
• Inventors: Bozzolato, Giovanni
• Primary Examiner(s): Rosenberger, R. A.
• Assistant Examiner(s): Cooper, Crystal D.
• Application Number:
  US06/615,839
• Time in Patent Office: 985 Days
• Field of Search: 356/2, 356/12, 356/14
• US Class Current: 356/2
• CPC Class Codes: G01C 11/00 Photogrammetry or videogrammetry, e.g. stereogrammetry; Photographic surveying

Abstract

A method for the stereophotogrammetric survey of a large-dimension object is provided in which the object and a chain having two reference markers thereon spaced apart at a known distance are photographed from a height of about 30 m with two synchronized metric photographic cameras spaced apart by about 6 m. Depth measurements (Z axis) are made on a stereoscopic model reproduced by a stereoplotter at eight sets of points grouped in the eight conventional perimetral locations of photogrammetric orientation at the crests and troughs of the ripples or undulations of the water or ground, respectively. The mean of the depth measurements is calculated to determine the mean horizontal plane and the model is correctly orientated with respect to the horizontal plane by suitable rotation. The length of the chain is measured between the two reference markers on the orientated model and the ratio of the chain length measured on the model to the known length of the catenary arc between the markers is used to determine the reproduction scale.

Claims

1. A method for the stereophotogrammetric survey of large dimension objects situated on the sea comprising:

(i) providing two synchronized metric photographic cameras mounted apart from one another at a known distance of about 6 meters in parallel orientation at a distance of about 30 meters from the object to be surveyed;

(ii) providing an inextensible chain in full view of said cameras within the area to be surveyed, said chain having two reference markers mounted thereon at a known distance from each other, said markers being of sufficient size to be reliably visible on photograms taken from a distance of about 30 to 40 meters, the links of said chain also being of sufficient size to be visible on photograms taken from a distance of about 30 to 40 meters;

(iii) simultaneously photographing the object to be surveyed and said inextensible chain with said synchronized metric photographic cameras to provide two simultaneous photographs of the object and said chain;

(iv) obtaining a stereoscopic optical model of the object to be measured from said two simultaneous photographs by means of a stereoplotter;

(v) measuring on said stereoscopic optical model eight sets of points grouped in the eight conventional perimetral locations of photogrammetric orientation, one half of said points being situated at the crest level and the other half of said points being situated at the trough level of waves of the sea;

(vi) statistically processing said crest and trough measurements to determine the mean horizontal plane;

(vii) orientating said stereoscopic optical model on said mean horizontal plane by suitable rotation of said stereoscopic optical model;

(viii) measuring on said stereoscopic optical model in the photographic scale the length of the catenary arc between said two reference markers by summing the lengths of the small arc portions corresponding to each link of said chain;

(ix) determining the scale of said stereoscopic optical model by comparing said measured length of said catenary arc to the known distance between said reference markers on said inextensible chain; and

(x) calculating actual dimensions of the object by measuring linear distances on said stereoscopic optical model and converting said measured linear distances into actual object dimensions using said stereoscopic optical model scale.

2. The method according to claim 1 wherein said two synchronized metric photographic cameras are mounted apart at a known distance by being mounted at each end of a beam constructed of high-strength metal.

3. The method according to claim 2 wherein said beam is mounted in cantelever fashion projecting from the two side doors of a helicopter.

4. The method according to claim 2 wherein said beam is installed by a cage supported by a crane.

5. A method for the stereophotogrammetric survey of large dimension objects situated on land comprising:

(i) providing two synchronized metric photographic cameras mounted apart from one another at a known distance of about 2 meters in parallel orientation at a distance of about 30 meters from the object to be surveyed;

(ii) providing an inextensible chain in full view of said cameras within the area to be surveyed, said chain having two reference markers mounted thereon at a known distance from each other, said markers being of sufficient size to be reliably visible on photgrams taken from a distance of about 30 to 40 meters, the links of said chain also being of sufficient size to be visible on photgrams taken from a distance of about 30 to 40 meters;

(iii) simultaneously photographing the object to be surveyed and said inextensible chain with said synchronized metric photographic cameras to provide two simultaneous photographs of the object and said chain;

(iv) obtaining a stereoscopic optical model of the object to be measured from said two simultaneous photographs by means of a stereoplotter;

(v) measuring on said stereoscopic optical model eight sets of points grouped in the eight conventional perimetral locations of photogrammetric orientation, one half of said points being situated at the maximum level and the other half of said points being situated at the minimum level of the ground undulations;

(vi) statistically processing said maximum and minimum ground undulation measurements to determine the mean horizontal plane;

(vii) orientating said stereoscopic optical model on said mean horizontal plane by suitable rotation of said stereoscopic optical model;

(viii) measuring on said stereoscopic optical model in the photographic scale the length of the catenary arc between said two reference markers by summing the lengths of the small arc portions corresponding to each link of said chain;

(ix) determining the scale of said stereoscopic optical model by comparing said measured length of said catenary arc to the known distance between said reference markers on said inextensible chain; and

(x) calculating actual dimensions of the object by measuring linear distances on said stereoscopic optical model and converting said measured linear distances into actual object dimensions using said stereoscopic optical model scale.

6. The method according to claim 5 wherein said two synchronized metric photographic cameras are mounted apart at a known distance by being mounted at each end of a beam constructed of high-strength metal.

7. The method according to claim 6 wherein said beam is mounted in cantelever fashion projecting from the two side doors of a helicopter.

8. The method according to claim 7 wherein said beam is installed on a cage supported by a crane.