Космические снимки, цифровые карты, геоинформационные системы

Photoplotting

 

Today the use of the earth remote sensing data (of satellite and aerial survey) is the most expedient and cost-effective solution for the creation of surface and terrain digital models and for the update of the existing topographic maps.

 

In most cases, the geometry of produced images is accompanied by scale distortions in the field of a shot. These distortions are caused by the lean of the camera optical axis from the vertical position at the moment of survey, by the relief displacement, by the orbit inclination of the survey etc. As a result, the carrying out of the shot accurate measurements is accompanied by considerable errors. For the reconstruction of the image geometry it is necessary to apply the photoplotting methods and technologies.

 

The one-to-one correspondence between the points in the shot and the analogous points located on the earth surface is established during the photoplotting. Geometric distortions of the shot are thus corrected.

 

Orthotransformation is the main and the most effective method to take into account the relief displacement errors during the image processing. The influence of such displacements is especially critical for the shots of terrain where the relief is characterized by the significant level difference.

 

A planimetrically accurate image of the earth surface is created in the process of orthotransformation, this image precisely represents the surface and its characteristics. Besides, the impact of the camera or sensor orientation and the camera or sensor systematic errors are taken into account.

 

Our company has successfully accomplished a lot of projects in the creation of both single orthophotos and orthoimage mosaics.

 

As the example can be given the project, the purpose of which was to provide digital orthophotos in the territory of a number of European cities based on the materials of space images got from the satellite Quickbird. Digital maps and plans of 1:25,000 and 1:10,000 scale were used as the additional material.

 

After photoplotting (fig. 1) the geometric distortions were corrected and orthotransformed images in the UTM system of coordinates in the WGS-84 ellipsoid were received. The minimal resolution of the raster image according to the customer’s requirements was 5 m. The positional accuracy corresponds to 10 m in plan view. The format of the supplied finished images was GeoTIFF.

 

The used software was LPS (ERDAS).

 

Another example of the projects in the creation of image mosaics was the project to create orthotransformed aerial image mosaic for the territory along the “Nothern areas of Tyumen region –TORZHOK” gas main pipeline with the additional color correction. The total extension of the route survey was more than 2.5 thousand km.

 

 

The usage of modern processing technologies and the newest software permits the specialists of our company quickly and qualitatively carry out the projects with different degree of complexity.