Week Eight: Viva la Resolution!

Over the weeks we've figured out different things about remote sensing with satellites: their precursors, their uses, how they orbit in Earth, and the electromagnetic radiation they pick up.  The question still remains, how does a satellite pick up this information?  How can one satellite see heat while another sees infrared light, or more broadly, what creates differences between satellites?  Some important distinctions between satellites are their resolutions. 

There are four different types of resolution concerning remote sensing: spatial resolution, spectral resolution, radiometric resolution, and temporal resolution.  All these factor in to the type of information a satellite is able to gather, and they are important to further understanding on how satellites really work.

Spatial resolution is one of the simplest distinguishers between satellites.  It is basically the smallest feature a satellite is able to distinguish.  This is also the pixel size of an object.  An example of spatial resolution that I’m sure almost everyone reading this has experienced is whenever we try to make a picture bigger, and it turns into a blur of squares.  An easy way to think of spatial resolution is that the bigger you can make a photo without it turning into squares, the higher the spatial resolution.

 

high spatial resolution → low spatial resolution

Source: http://coast.noaa.gov/geozone/you-say-you-want-high-resolution/

 

Next, spectral resolution determines what types of electromagnetic wavelengths a satellite can pick up.  The finer the spectral resolution, the smaller waves the satellite can distinguish.  This is the difference between black and white film and color film.  Black and white film lumps all the different colors together and sees them as either black or white.  Alternately, the finer resolution of color film allows the sensor to distinguish between different colors.

 

                                       

 Different spectral resolutions

Source: http://www.nrcan.gc.ca/earth-sciences/geomatics/satellite-imagery-air-photos/satellite-imagery-products/educational-resources/9407

Radiometric resolution relates to spectral resolution concerning the quality of a satellite image.  Spectral resolution determines the amount of pixels in an image, but the radiometric resolution affects how the satellite discerns differences in energy (think of shading in a photograph being either very gradual or very abrupt).

                                       

Examples of differences in radiometric resolution

Source: http://www.slideshare.net/merdevie/remote-sensing-10526190

Lastly, temporal resolution is the amount of time it takes a satellite to pass over the same place on Earth again.  This is important for what purpose the satellite has.  For a LANDSAT, the temporal resolution is 16 days.  If we want to see a real time event from the air, then we would want a satellite with faster temporal resolution.

Bibliography:

Intermap Technologies Ltd. Tutorial: Fundamentals of Remote Sensing. Ottawa: Canada Centre for Remote Sensing, 2013. Print.