Photographic "Footprints", definitions thereof |
Photographic "Footprints", definitions thereof |
Jun 28 2017, 02:07 AM
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#1
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Junior Member Group: Members Posts: 91 Joined: 21-August 06 Member No.: 1063 |
Concerning the definition of a "footprint"
Say a spacecraft flying overhead of planet is pointing its camera rectangular shaped FOV down at the surface. If 1 or more of the 4 corner boundary rays stops intercepting with the surface, is the area under the FOV still considered a "footprint"? Perhaps it only matters if the borsight ray of the FOV intercepts with the planet to qualify as a "footprint" ? I tend to think all of those 4 cornors rays would have to be intecepting the surface to qualify as a "footprint" but I just wanted some clarification maybe from an expert. Thank you. |
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Jun 28 2017, 05:35 AM
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#2
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Member Group: Admin Posts: 976 Joined: 29-September 06 From: Pasadena, CA - USA Member No.: 1200 |
Corners not necessarily define the footprint of a sensor. A camera lens distorts the field of view even when pointed perpendicular to a surface. A fish-eye lens is obviously an extreme of this, but even carefully designed lens have the same problem. Then consider that not every observation is done nadir to the surface, so the footprint can vary in shape quite considerably. The projection of the sensor onto the surface depends on the surface as well. Then you have sensors like CRISM that swing across track giving a butterfly wings footprint.
Paolo -------------------- Disclaimer: all opinions, ideas and information included here are my own,and should not be intended to represent opinion or policy of my employer.
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Jun 28 2017, 06:26 PM
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#3
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Junior Member Group: Members Posts: 91 Joined: 21-August 06 Member No.: 1063 |
Corners not necessarily define the footprint of a sensor. A camera lens distorts the field of view even when pointed perpendicular to a surface. A fish-eye lens is obviously an extreme of this, but even carefully designed lens have the same problem. Then consider that not every observation is done nadir to the surface, so the footprint can vary in shape quite considerably. The projection of the sensor onto the surface depends on the surface as well. Then you have sensors like CRISM that swing across track giving a butterfly wings footprint. Paolo Thank you Paolo |
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Jun 28 2017, 07:57 PM
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#4
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Senior Member Group: Members Posts: 2542 Joined: 13-September 05 Member No.: 497 |
If 1 or more of the 4 corner boundary rays stops intercepting with the surface, is the area under the FOV still considered a "footprint"? If an image contains the entire target planet, then none of the four corners intersect the planet, and if the planet were off-center, the boresight might not intersect the planet either, but the footprint would still be the entire visible part of the planet. -------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
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Jun 28 2017, 09:55 PM
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#5
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Merciless Robot Group: Admin Posts: 8785 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
Edited topic title for clarity.
-------------------- A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
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