Choose a radar mode

A regional ice service and a team inspecting a small flood-damaged site need different views. Synthetic aperture radar builds an image from microwave echoes collected as the platform moves. RCM 1 and its companions use C-band radar, but the resulting product depends on the selected observation mode. The mission is not one fixed-resolution camera.

Consider two entries in CSA’s published mode table: a low-resolution mode pairs roughly 100-metre resolution with a 500-kilometre swath, while a 5-metre high-resolution mode has a 30-kilometre swath. Swath is the width of the observed strip; resolution describes the scale at which detail can be separated under the stated conditions. The finest available detail therefore does not automatically provide the widest view.

For a first survey of a very large coastal area, broad coverage can reveal where a closer look is useful. For a small target, finer detail may be appropriate. State the purpose before selecting a mode, and check the product specification rather than assuming one headline number applies to every image.

In an original simplified grid model, a 10 km by 10 km study area covers 100,000,000 square metres. Square cells 100 m on a side cover 10,000 square metres each, giving 10,000 cells. At 5 m per side, each cell covers 25 square metres, giving 4,000,000 cells: 400 times as many.

This is a sampling-grid calculation, not a prediction of an RCM file size. Actual image sampling can differ from spatial resolution; compression, data type, channels and metadata also affect storage. More cells do not by themselves prove that an instrument resolves proportionally more independent information.

A narrow ship can produce a detectable radar return without its shape being resolved into a detailed portrait. Detection asks whether evidence of a target is present; resolution asks whether nearby features can be distinguished. Identification asks what that target is. Keep those questions separate when explaining an image.

Coverage and detail answer different needs

Polarization describes the orientation of the transmitted and received electromagnetic field. Radar products can combine different polarization measurements in a color display. Those colors represent assigned measurements, not the visible colors a person would see from the spacecraft.

Viewing angle also changes how a surface scatters energy back to the radar. A brighter field in one image can reflect a different angle, moisture state or processing choice rather than a new building. Record the satellite, beam mode, polarization, acquisition time, calibration and viewing geometry before comparing scenes.

For this lesson’s planning exercise, keep two products: a broad survey for context and a targeted detailed image for the smaller question. Explain each product’s limits. Upscaling the broad survey on a screen cannot recover detail that the measurement never resolved.