Warsaw (Poland)

It is a subsample of Landsat TM product ( bands 3,4,7).
The image shows the town of Warsaw (Poland) and the surrounding area.
The town (upper right half of the image) was built along the Wista River just before the confluence with the outlet from the Zegrzynskie Lake. The oldest part of the town is located close to the river banks, while the later urban growth took place towards the south. In particular, the town expanded along the Warsaw-Piaseczno road and the railway to Pruszkow, Grodzisk Maz and Zyrardow, south-west of the city centre.
The main urban roads form a grid in the centre of the town and then leave in a radial pattern.
The vegetation in the surroundings consists of both small agricultural fields (grey) south of the urban settlements and small forested areas (green), located mainly west and north of Warsaw.

( Product: ERS-1 SAR.PRI
Red: 27/08/1992,
Green: 18/06/1992,
Blue: 1/10/1992 )

In comparison to the Landsat Thematic Mapper image the Radar image has a rather similar image content but it appears less focused because of the inherent image noise. However the radar image provide additional information on the type and also of the arrangements of buildings.
In general the brighter a built-up area the denser the constructions, industrial plants are also brightly imaged because of the metallic structures. But in some case the casual alignment of long edifices parallel to the satellites flight pass may result in very bright quarters. This seems the case in two areas to the right (east) of the larger airport in the image.

Bridges are also well visible and their form and brightness in the image may reveal the type of construction.
Woods appear in a homogeneous greyish green and therefore can be well delineated. Agricultural field are represented in various colours.
Due to the combination of acquisition dates including June, August and October one can assume that green and yellowish fields are wheat, while reddish fields contain late crop (potato, corn, sugarbeet, etc.) Especially for crop monitoring Radar offers the advantage to provide data when it is required, independent of cloud-coverage, which in the case of conventional data (from Landsat or Spot) represents the main obstacle to reliable data availability.

The subsection in full resolution provides more details in the vicinity of the large airport.

The confrontation of optical data with unfiltered (left part) and filtered (right part) Radar data demonstrates the limited use of sophisticated filtering processes .
Although image noise is much reduced and digital classification with statistical methods can be made; for visual image interpretation information might well be lost on the filtered image, especially in less denser built-up residential area, with smaller houses, gardens and large trees.

(Eurimage, Rome and ERS Data Utilization Section, ESA/ESRIN)

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry