Photoclinometry, or shape-from-shading, is the process by which a 2-dimensional image of a surface is transformed into a surface map that represents different levels of elevation. It uses the shadows and light direction as reference points. It is used mostly to depict the surface of sculptures, to give an idea of how it would look in 3-dimensions. The techniques depend on very specific conditions, especially light direction.
When light bounces off an object, it reflects with location-specific brightness that depends on the shape of the object and the position of the lighting source. This reflection map can be used to create a bump map of a surface, which uses grayscale levels to depict the height of a point on a surface. Knowing the direction and angle of the light source, one can calculate the approximate height that a point has. However, the light direction and angle is usually unknown, which leads to poor quality images, or having to create multiple bump maps, each time trying different settings.
Usageedit
Some artists use photoclinometry to digitize a 3-dimensional representation of a sculpture.
Glaciologists have used photoclinometry to characterize the surfaces of Antarctica[5] and Greenland.[6] Repeat photoclinometry is a method of building surfaces from a series of satellite image to investigate changes in ice sheet topography over time.[7]
Photoclinometry has been used to measure volcanic plume top topography on Earth. [8]
Problemsedit
Light direction is very important to the quality of a photoclinometric image. Light that comes from directly over the surface (behind the camera) makes it hard to distinguish the shadows. Multiple light sources are also a problem, since they destroy important shadows required for the algorithms to work properly.
In order to solve these problems, new missions to other planets plan to use a process similar to stereoscopy in order to get a more accurate depiction of the surface on another planet. The Mars Reconnaissance Orbiter is one of the mission that attempts to do this. This process uses two images of one location taken from two separate lens on a camera, much in the same way humans do with their eyes. By using two images, they can get a 3-dimensional perspective of objects on the surface like we do.
^Wildey, R (1975). "Generalized photoclinometry for Mariner 9". Icarus. 25 (4): 613–626. Bibcode:1975Icar...25..613W. doi:10.1016/0019-1035(75)90043-3.
^Hargitai, Henrik; Willner, Konrad; Buchroithner, Manfred (2019), Hargitai, Henrik (ed.), "Methods in Planetary Topographic Mapping: A Review", Planetary Cartography and GIS, Lecture Notes in Geoinformation and Cartography, Springer International Publishing, pp. 147–174, doi:10.1007/978-3-319-62849-3_6, ISBN978-3-319-62849-3, S2CID 133855780
^van Diggelen, J (July 1951). "A photometric investigation of the slopes and the heights of the ranges of hills in the maria of the moon". Bull. Astron. Inst. Netherlands. 11: 283. Bibcode:1951BAN....11..283V.
^Howard, Alan D.; Blasius, Karl R.; Cutts, James A. (1982). "Photoclinometric determination of the topography of the Martian north polar cap". Icarus. 50 (2–3): 245–258. Bibcode:1982Icar...50..245H. doi:10.1016/0019-1035(82)90125-7.
^Bidschadler, R. A.; Vornberger, P. L. (1994). "Detailed elevation map of Ice Stream C, Antarctica, using satellite imagery and airborne radar". Annals of Glaciology. 20: 327–335. Bibcode:1994AnGla..20..327B. doi:10.3189/1994aog20-1-327-335. ISSN 0260-3055.
^Scambos, Ted A.; Haran, Terry (2002). "An image-enhanced DEM of the Greenland ice sheet". Annals of Glaciology. 34: 291–298. Bibcode:2002AnGla..34..291S. doi:10.3189/172756402781817969. ISSN 0260-3055.
^Greene, C. A.; Blankenship, D. D. (2017). "A Method of Repeat Photoclinometry for Detecting Kilometer-Scale Ice Sheet Surface Evolution". IEEE Transactions on Geoscience and Remote Sensing. PP (99): 2074–2082. doi:10.1109/tgrs.2017.2773364. ISSN 0196-2892. S2CID 4348022.
^Glaze, Lori S.; Wilson, Lionel; Mouginis-Mark, Peter J. (1999-02-10). "Volcanic eruption plume top topography and heights as determined from photoclinometric analysis of satellite data". Journal of Geophysical Research: Solid Earth. 104 (B2): 2989–3001. Bibcode:1999JGR...104.2989G. CiteSeerX10.1.1.572.9109. doi:10.1029/1998jb900047. ISSN 2156-2202.
Further readingedit
Kirk, Randolph L., Barrett, Janet M., Soderblom, Laurence A. (2003) Photoclinometry Made Simple...? Advances in Planetary Mapping.[1]
McEwen, Alfred S (1991). "Photometric functions for photoclinometry and other applications". Icarus. 92 (2): 298–311. Bibcode:1991Icar...92..298M. doi:10.1016/0019-1035(91)90053-v.
Wilson, L.; Hampton, J. S.; Balen, H. C. (1985). "Photoclinometry of Terrestrial and Planetary Surfaces". Lunar and Planetary Science. XVI: 912–913. Bibcode:1985LPI....16..912W.
External linksedit
Shape from Shading - Photoclinometry
USGS Geomatics
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Photoclinometry or shape from shading is the process by which a 2 dimensional image of a surface is transformed into a surface map that represents different levels of elevation It uses the shadows and light direction as reference points It is used mostly to depict the surface of sculptures to give an idea of how it would look in 3 dimensions The techniques depend on very specific conditions especially light direction Contents 1 The process 2 Usage 3 Problems 4 See also 5 References 6 Further reading 7 External linksThe process editWhen light bounces off an object it reflects with location specific brightness that depends on the shape of the object and the position of the lighting source This reflection map can be used to create a bump map of a surface which uses grayscale levels to depict the height of a point on a surface Knowing the direction and angle of the light source one can calculate the approximate height that a point has However the light direction and angle is usually unknown which leads to poor quality images or having to create multiple bump maps each time trying different settings Usage editSome artists use photoclinometry to digitize a 3 dimensional representation of a sculpture Geologists and those that study planetary science use it to get an idea of how the surface of a planet looks like 1 and generate topographic maps and digital elevation models see photometric stereo 2 Planetary applications began with investigations of lunar topography as early as 1951 3 and has since been applied to the Martian surface 4 Glaciologists have used photoclinometry to characterize the surfaces of Antarctica 5 and Greenland 6 Repeat photoclinometry is a method of building surfaces from a series of satellite image to investigate changes in ice sheet topography over time 7 Photoclinometry has been used to measure volcanic plume top topography on Earth 8 Problems editLight direction is very important to the quality of a photoclinometric image Light that comes from directly over the surface behind the camera makes it hard to distinguish the shadows Multiple light sources are also a problem since they destroy important shadows required for the algorithms to work properly In order to solve these problems new missions to other planets plan to use a process similar to stereoscopy in order to get a more accurate depiction of the surface on another planet The Mars Reconnaissance Orbiter is one of the mission that attempts to do this This process uses two images of one location taken from two separate lens on a camera much in the same way humans do with their eyes By using two images they can get a 3 dimensional perspective of objects on the surface like we do See also editPhotometric stereo Photogrammetry Stereoscopy Bump mappingReferences edit Wildey R 1975 Generalized photoclinometry for Mariner 9 Icarus 25 4 613 626 Bibcode 1975Icar 25 613W doi 10 1016 0019 1035 75 90043 3 Hargitai Henrik Willner Konrad Buchroithner Manfred 2019 Hargitai Henrik ed Methods in Planetary Topographic Mapping A Review Planetary Cartography and GIS Lecture Notes in Geoinformation and Cartography Springer International Publishing pp 147 174 doi 10 1007 978 3 319 62849 3 6 ISBN 978 3 319 62849 3 S2CID 133855780 van Diggelen J July 1951 A photometric investigation of the slopes and the heights of the ranges of hills in the maria of the moon Bull Astron Inst Netherlands 11 283 Bibcode 1951BAN 11 283V Howard Alan D Blasius Karl R Cutts James A 1982 Photoclinometric determination of the topography of the Martian north polar cap Icarus 50 2 3 245 258 Bibcode 1982Icar 50 245H doi 10 1016 0019 1035 82 90125 7 Bidschadler R A Vornberger P L 1994 Detailed elevation map of Ice Stream C Antarctica using satellite imagery and airborne radar Annals of Glaciology 20 327 335 Bibcode 1994AnGla 20 327B doi 10 3189 1994aog20 1 327 335 ISSN 0260 3055 Scambos Ted A Haran Terry 2002 An image enhanced DEM of the Greenland ice sheet Annals of Glaciology 34 291 298 Bibcode 2002AnGla 34 291S doi 10 3189 172756402781817969 ISSN 0260 3055 Greene C A Blankenship D D 2017 A Method of Repeat Photoclinometry for Detecting Kilometer Scale Ice Sheet Surface Evolution IEEE Transactions on Geoscience and Remote Sensing PP 99 2074 2082 doi 10 1109 tgrs 2017 2773364 ISSN 0196 2892 S2CID 4348022 Glaze Lori S Wilson Lionel Mouginis Mark Peter J 1999 02 10 Volcanic eruption plume top topography and heights as determined from photoclinometric analysis of satellite data Journal of Geophysical Research Solid Earth 104 B2 2989 3001 Bibcode 1999JGR 104 2989G CiteSeerX 10 1 1 572 9109 doi 10 1029 1998jb900047 ISSN 2156 2202 Further reading editKirk Randolph L Barrett Janet M Soderblom Laurence A 2003 Photoclinometry Made Simple Advances in Planetary Mapping 1 McEwen Alfred S 1991 Photometric functions for photoclinometry and other applications Icarus 92 2 298 311 Bibcode 1991Icar 92 298M doi 10 1016 0019 1035 91 90053 v Wilson L Hampton J S Balen H C 1985 Photoclinometry of Terrestrial and Planetary Surfaces Lunar and Planetary Science XVI 912 913 Bibcode 1985LPI 16 912W External links editShape from Shading Photoclinometry USGS Geomatics nbsp This photography related article is a stub You can help Wikipedia by expanding it vte Retrieved from https en wikipedia org w index php title Photoclinometry amp oldid 1194886539, wikipedia, wiki, book, books, library,
