Synthetic aperture radar(SAR) - point target Doppler history

Target position
Range index
Azimuth index

Animation control
Azimuth speed
Set azimuth idx
Reset camera

Results
AZ_IDX	1520
X	3636709.9791
Y	1256100.6216
Z	6033877.2945
Doppler	16577.25	Hz
R	854206.20	m
RCM	236.6482

Data provided by:

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Data attribution

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Imagery

Cesium ion

Bing Maps Aerial

Bing Maps Aerial with Labels

Bing Maps Roads

Sentinel-2

Blue Marble

Earth at night

Natural Earth II

Other

ArcGIS World Imagery

ArcGIS World Hillshade

Esri World Ocean

Open­Street­Map

Stadia x Stamen Watercolor

Stadia x Stamen Toner

Stadia Alidade Smooth

Stadia Alidade Smooth Dark

Terrain

Cesium ion

WGS84 Ellipsoid

Cesium World Terrain

MouseTouch

	Pan view Left click + drag
	Zoom view Right click + drag, or Mouse wheel scroll
	Rotate view Middle click + drag, or CTRL + Left/Right click + drag

	Pan view One finger drag
	Zoom view Two finger pinch
	Tilt view Two finger drag, same direction
	Rotate view Two finger drag, opposite direction

May 1 202502:20:51 UTC1x

May 1 2025 00:00:00 UTCMay 1 2025 06:00:00 UTCMay 1 2025 12:00:00 UTCMay 1 2025 18:00:00 UTCMay 2 2025 00:00:00 UTCMay 2 2025 06:00:00 UTC

May 2 2025 06:00:00 UTC

Graphs of results

UI Color code

• BLUE rectangle like shape on the ground indicates a positive Doppler effect, up to +0.5 PRF - a blue shift
• RED rectangle like shape on the ground indicates a negative Doppler effect, down to -0.5 PRF - a red shift
• WHITE lines indicate the near and far range of the zero Doppler line
• ORANGE line indicates the time when the point target Doppler effect is between +- 0.5 PRF
• ORANGE point is the geolocated point target

Information

• The animation simulates and visuzalized the core the principles of SAR - the azimuth FM modulation
• A freely chosen place on the ground is chosen as a reference point target, the satellite orbit state vectors are used to calculate the geometry of the overflight
• The BLUE/RED visualization on the ground only shows areas of +-0.5 PRF Doppler frequency on the ground. Ideally, the SAR antenna beam center is directed at zero Doppler line and every point on the ground only produces azimuth Doppler data within +- 0.5 PRF, however real life is much more complicated.
• The Doppler frequency changes close to linearly in respect to azimuth index, thus this called an azimuth chirp and this used to compress the Doppler history in azimuth compression
• RCM - Range Cell Migration - as the target is in the +- 0.5 PRF area, the range index of the target changes as in azimuth direction. This is a major issue in azimuth compression
• V_r can be deduced from the R graph, via fitting data to R²(n) = R0² + V_r²(n)²

Metadata input:

TODO/Ideas

• Envisat model orientiation
• BLUE/RED polygon gradients, to visualize increasing/decreasing Doppler shifts
• Actually calculate V_r
• Visualize radar pulses?
• Visualize Doppler Centroid on the animation
• Visualize RCM on a 2d picture?