lidar and satellite imagery

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03-28-2014 03:01 AM
TammyHardesty
New Contributor
I have a las file (and the las dataset I made from it) that aren't preclassified for the buildings.  Is there a way I can construct building rooftops by doing a spatial join to satellite imagery?  I'm a student who has never worked with las files or las datasets before, so
please, ELI5
Thank you in advance!
Tammy
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GrljAles
Occasional Contributor
Hi,
The idea is that you create DEM and DSM (Digital Surface Model). For this purpose I've been using some Las Tools scripts. The difference between DSM and DEM is so called normalised DEM representing only objects above the ground level. Then it depends how is the buliding defined in your country. In my country building is higher than 2 m so I had to exclude also obyects lower than this limit.
NDEM includes also the tree tops so high resolution satellite images or Digital Orto Photos with infra red band are needed to calculate Normalised Difference Vegetation Index that has to be reclassified to include only green surfaces. Reclassifying areas in nDEM that are covered with NDVI mask to nulls should give you the rooftops but this is only the simplified version of the procedure.

Here is one article about this: http://www.google.si/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&ved=0CEIQFjAC&url=http%3A%2F%2Fwww.dli...

The ful version of the PHD is here but unfortunately only in Slovenian language I think: http://drugg.fgg.uni-lj.si/781/1/GED_0197_Grigillo.pdf
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