Using space images for topographic maps updating

Topographic maps

Topographic maps make a presentation of our surroundings, giving us a chance to take our bearings in it, featuring all visible territory elements in the same detail. The maps depict the relief, hydrography, vegetation, soil and subsoil, human settlements, road networks, socio-economic and other facilities, which allows us to make a complex evaluation of the territory. The usual topographic map scale ranges from 1:10 000 to 1: 200 000.

As of today, there are almost no blank spots on the map of the world. Topographic maps cover basically all the land surface of our planet, however, not all of them are equally detailed. By 1988, the territory of Russia was completely covered with maps at the scale of 1:25 000, and about one-third of the country – at the scale of 1:10 000. However, most of these maps are not regularly updated.

Meanwhile, the modern world is very dynamic: cities are growing, new settlements appear, new roads, communications networks and engineering facilities are being constructed, new areas of natural resources recovery are being developed, forests are cut, and land use structure is changing. Therefore, topographic maps are always subject to updating. Since the state topographic maps of Russia in basic scales have already been generated, new maps drawings are not frequently required – only in case of some dramatic changes, such as building of new towns or big facilities.

1:25 000 topographic map. Territory status in 1994	IRS-1D LISS/PAN image, merged in natural colors. Spatial resolution: processed to 6 m. Acquisition date: May 22, 2002. Genenjik area. Yellow line indicates the coast line limit according to the topographic map at a scale of 1:25 000. The image enables to verify the coast line limits (1) and put on new objects, for example landing docks (2).

Aerial photos have been traditionally used as the primary source for the topographic maps drawing. Satellite-based digital images open new horizons: cheaper repeated imagery, increased territory coverage and decreased relief distortions. Besides, generalization on the small-scale maps becomes simpler: instead of time-consuming simplification of big-scale maps, it is possible to use medium resolution space images directly. Therefore, satellite-based imagery is used increasingly wider and may soon become the principle method of topographic maps updating. When choosing an image for mapping in certain scales, the graphical accuracy of maps drawing and printing is accounted for (0.1 mm). For example, the images should have a spatial resolution of at least 100 m for the maps at a scale of 1:1 000 000 and at least 10 m for 1:100 000 maps.

forward »