[Liblas-commits] hg: examples for assigning color information from
rasters
liblas-commits at liblas.org
liblas-commits at liblas.org
Fri Dec 17 22:21:45 EST 2010
changeset 3bb734e126b0 in /Volumes/Data/www/liblas.org/hg
details: http://hg.liblas.orghg?cmd=changeset;node=3bb734e126b0
summary: examples for assigning color information from rasters
diffstat:
doc/start.txt | 107 ++++++++++++++++++++++++++++++++++++++++-----
doc/utilities/las2las.txt | 10 ++-
2 files changed, 100 insertions(+), 17 deletions(-)
diffs (178 lines):
diff -r d44837072a6a -r 3bb734e126b0 doc/start.txt
--- a/doc/start.txt Fri Dec 17 13:04:42 2010 -0600
+++ b/doc/start.txt Fri Dec 17 21:21:37 2010 -0600
@@ -141,11 +141,12 @@
Min X, Y, Z: -83.43, 39.01, 170.58,
Max X, Y, Z: -83.43, 39.01, 170.76,
-The ``srs.las`` file had a scale of 0.01, or two decimal places of precision
-for its X, Y, and Z coordinates. For UTM data, this is ok, because it implies
-an implicit precision of 1 cm. For decimal degree data of the unprojected plate carrée
-coordinate system, it causes us to lose a bunch of precision. We need to
-set our scale values to something that can hold more precision in our case:
+The ``srs.las`` file had a scale of 0.01, or two decimal places of precision
+for its X, Y, and Z coordinates. For UTM data, this is ok, because it implies
+an implicit precision of 1 cm. For decimal degree data of the unprojected
+Plate Carrée coordinate system, it causes us to lose a bunch of precision. We
+need to set our scale values to something that can hold more precision in our
+case:
::
@@ -170,14 +171,15 @@
add a twist -- we want to change the vertical datum on the data from WGS84
to NAVD88.
-.. warning::
+.. warning:
- A number of requirements are needed before you can do vertical datum transformations
- with libLAS. The most important is GDAL, of course, but you also need a
- very current (possibly even unreleased) version of `Proj.4`_ and the vertical
- datum .gtx transformation files. If you're using :ref:`osgeo4w_install`, you
- already have all of this installed when you installed libLAS. For Linux
- or other Unix platforms, you should be aware of these requirements.
+ A number of requirements are needed before you can do vertical datum
+ transformations with libLAS. The most important is GDAL support, of course,
+ but you also need a very current (possibly even unreleased) version of
+ `Proj.4`_ and the vertical datum .gtx transformation files. If you're using
+ :ref:`osgeo4w_install`, you already have all of this installed when you
+ installed libLAS. For Linux or other Unix platforms, you should be aware of
+ these requirements.
Assuming you have all of the prerequisites in place, we can do the vertical
datum transformation quite simply (again, worrying about precision as well):
@@ -192,6 +194,83 @@
other ways to have these operations happen using `WKT`_ and even GeoTIFF
keys, but this is the most simple way to do things via command line.
+Assigning color information to a LAS file
+..............................................................................
+
+.. note::
+
+ The following example assumes you are working with the `Autzen_Stadium`_
+ example file that is available from the http://liblas.org/sample sample
+ library.
+
+
+Frequent availability of combined terrestrial LiDAR and image captures means
+that its now possible to obtain .las files that you can stylize with RGB
+imagery. The LAS 1.2 specification provides two different point data
+types that allow storing RGB data as 16 bit integers, but the tools to
+do the actual intersection operation have been somewhat limited.
+
+libLAS 1.6+ allows you to assign color information to a .las file if `GDAL`_
+is linked in at compile-time.
+
+.. note::
+ The :ref:`LAS specifications <specifications>` only allow two different
+ point format types to store color information -- point format 2 and point
+ format 3. The difference between point format 2 and point format 3 is that
+ 3 also has time stored on it. Additionally, only LAS 1.2 and 1.3 versions
+ support storing color information, but libLAS only can write LAS 1.2 as of
+ libLAS 1.6.0.
+
+
+
+1. Unzip the `Autzen Stadium <Autzen_Stadium>`_ data.
+
+ ::
+
+ $ unzip Autzen_Stadium.zip
+ Archive: Autzen_Stadium.zip
+ creating: Autzen_Stadium/
+ inflating: Autzen_Stadium/image.tif
+ inflating: Autzen_Stadium/lidar.las
+
+2. Issue the :ref:`las2las <las2las>` call
+
+ ::
+
+ $ las2las -i lidar.las \
+ --color-source image.tif \
+ -o output.las \
+ --file-format 1.2 \
+ --point-format 3 \
+ -v
+
+ ::
+
+ Opening lidar.las to fetch Header
+ Setting format to: 1.2
+ Setting point format to: 3
+ Fetching color from ' image.tif' using bands '1, 2, 3' for R, G, B
+ Writing output:
+ - : output.las
+ 0...10...20...30...40...50...60...70...80...90...100 - done.
+
+3. Inspect the :ref:`lasinfo <lasinfo>` output and see color information
+ attached.
+
+ ::
+
+ lasinfo output.las
+
+ ...
+
+ Minimum Color: 39 56 56
+ Maximum Color: 252 254 251
+
+.. note::
+ :ref:`assign_color` contains more detailed information about this process.
+
+
+
.. _`CMake`: http://www.cmake.org/
.. _`CTest`: http://cmake.org/cmake/help/ctest-2-8-docs.html
.. _`CMake 2.8.0+`: http://www.cmake.org/cmake/help/cmake-2-8-docs.html
@@ -208,4 +287,6 @@
.. _`EPSG`: http://www.epsg-registry.org/
.. _`EPSG:4326`: http://spatialreference.org/ref/epsg/4326/
.. _`Proj.4`: http://trac.osgeo.org/proj/
-.. _`WKT`: http://en.wikipedia.org/wiki/Well-known_text#Spatial_reference_systems
\ No newline at end of file
+.. _`WKT`: http://en.wikipedia.org/wiki/Well-known_text#Spatial_reference_systems
+.. _`GDAL`: http://gdal.org
+.. _`Autzen_Stadium`: http://liblas.org/samples/Autzen_Stadium.zip
diff -r d44837072a6a -r 3bb734e126b0 doc/utilities/las2las.txt
--- a/doc/utilities/las2las.txt Fri Dec 17 13:04:42 2010 -0600
+++ b/doc/utilities/las2las.txt Fri Dec 17 21:21:37 2010 -0600
@@ -244,6 +244,7 @@
removes all VLRs from in.las when writing the new output.las file.
+.. _assign_color:
Adding color from an image
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -257,17 +258,17 @@
and sets the point format to ``3`` so it can store color information. It
also re-orders the color bands to have the 3rd band in the image be red, 1st
band be green, and second band be blue. Additionally, the color values are
-then multiplied by the --color-source-scale factor or 257 to rescale the
-8bit image data to 16bit color data.
+then multiplied by the --color-source-scale factor or 256 to rescale the
+8 bit image data to 16 bit color data.
::
las2las -i input.las \
--color-source image.img \
-o output.las \
- --format 1.2 \
+ --file-format 1.2 \
--point-format 3 \
- --color-source-scale 257 \
+ --color-source-scale 256 \
--color-source-bands 3 1 2
.. note::
@@ -275,6 +276,7 @@
coordinate system of the LAS file, you should use GDAL VRTs to cause the
image to be warped and reprojected as part of the read process. See
http://www.gdal.org/gdal_vrttut.html for more detail.
+
.. warning::
`GDAL`_ support must be enabled for this to work.
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