Context Navigation

r813	r835
5	5	:Author: Martin Isenburg
6	6	:Contact: isenburg@cs.unc.edu
	7	:Author: Howard Butler
	8	:Contact: hobu.inc@gmail.com
7	9	:Revision: $Revision$
8	10	:Date: $Date$
…	…
14	16	:backlinks: top
15	17
16		las2las reads and writes LIDAR data in the LAS format while modifing its
17		contents. Examples are clipping of points to those that lie within a
18		certain region specified by a bounding box (-clip), eliminating points that
19		are the second return (-elim_return 2), that have a scan angle above some
20		threshold (-elim_scan_angle_above 5), or below some intensity
21		(-elim_intensity_below 15). Another typical use may be to extract only
22		first (-first_only) returns or only last returns (-last_only). Extracting the
23		first return is actually the same as eliminating all others
24		(e.g.-elim_return 2 -elim_return 3, ...).
	18	Description
	19	-----------
25	20
	21	`las2las` reads and writes LiDAR data in the ASPRS LAS 1.0 and 1.1 formats while
	22	modifying its contents. While `lasinfo` can do a few simple operations like
	23	updating header information, more drastic changes, like removing points or
	24	altering values, will require `las2las`. `las2las` is expected to be used for
	25	modifying single files at a time, and all `las2las` operations require multiple
	26	read passes through the points. Some examples of operations `las2las` can be
	27	used for include:
26	28
27		Example usage
28		-------------
	29	* clipping of points to those that lie within a certain region specified
	30	by a bounding box (--clip)
	31	* eliminating points that are the second return (--eliminate_return 2),
	32	* eliminating points that have a scan angle
	33	above some threshold (--eliminate_scan_angle_above 5)
	34	* eliminating points that have an intensity below some
	35	threshold (--eliminate_intensity_below 15)
	36	* extracting only first (--first-only) or last (--last-only) returns
	37	* changing the format from LAS 1.0 to 1.1 or vice versa
	38	* eliminating points of a given classification (--eliminate class 2)
29	39
30		::
	40	`las2las` is a port of Martin Isenburg's `las2las` utility from `LASTools`_
	41	to the libLAS library. For the most part, it is unchanged from Martin's
	42	utility except for a few differences:
	43
	44	* Text output describing the operation(s) is only provided when the --verbose
	45	switch is provided.
	46
	47	* Provides some point validation
	48
	49	* Variable Length Records (VLRs) are carried forward by default.
	50
	51	* Supports format (1.1->1.0 & 1.0->1.1) conversion.
	52
	53	* GNU-style arguments and switches (although most of the switches used by
	54	Martin's utilities should continue to work).
31	55
32		$ las2las -i in.las -verbose
33
34		lists the value ranges of all the points (similar to lasinfo)
	56	Usage
	57	-----
35	58
36	59	Clipping with a rectangle
37		-------------------------
	60	~~~~~~~~~~~~~~~~~~~~~~~~~
38	61
39	62	::
40	63
41		$ las2las -~~i in.las -o out.las~~ -clip 63025000 483450000 63050000 483475000
	64	$ las2las --input in.las --output out.las --clip 63025000 483450000 63050000 483475000
42	65
43	66	clips points of in.las with x<63025000 or y<483450000 or x>63050000
44		or y>483475000 and stores surviving points to out.las. note that
	67	or y>483475000 and stores surviving points to out.las. Note that
45	68	clip expects the scaled integer values that the points are stored
46	69	with (not the floating point coordinates they represent).
47	70
48	71	Eliminating specified returns
49		-----------------------------
	72	~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
50	73
51	74	::
52	75
53		$ las2las -~~i in.las -o out.las~~ -eliminate_return 1
	76	$ las2las --input in.las --output out.las --eliminate_return 1
54	77
55	78	eliminates all points of in.las that are designated first returns by the
…	…
57	80
58	81	Limiting based on scan angle
59		----------------------------
	82	~~~~~~~~~~~~~~~~~~~~~~~~~~~~
60	83
61	84	::
62	85
63		$ las2las -~~i in.las -o out.las~~ -eliminate_scan_angle_above 15
	86	$ las2las --input in.las --output out.las --eliminate_scan_angle_above 15
64	87
65	88	eliminates all points of in.las whose scan angle is above 15 or below -15
…	…
67	90
68	91	Limiting based on intensity
69		---------------------------
	92	~~~~~~~~~~~~~~~~~~~~~~~~~~~
70	93
71	94	::
72	95
73		$ las2las -~~i in.las -o out.las -eliminate_intensity_below 1000 -remove_extra_header~~
74
	96	$ las2las --input in.las --output out.las --eliminate_intensity_below 1000
	97
75	98	eliminates all points of in.las whose intensity is below 1000 and stores
76		surviving points to out.las. in addition all variable headers and any
77		additional user headers are stripped from the file.
	99	surviving points to out.las.
78	100
79	101	Extract last returns
80		--------------------
	102	~~~~~~~~~~~~~~~~~~~~
81	103
82	104	::
83	105
84		$ las2las -~~i in.las -o out.las~~ -last_only
	106	$ las2las --input in.las --output out.las --last_only
85	107
86	108	extracts all last return points from in.las and stores them to out.las.
	109
	110	Throw out invalid data
	111	~~~~~~~~~~~~~~~~~~~~~~
	112
	113	::
	114
	115	$ las2las --input in.las --output out.las --skip_invalid
	116
	117	removes invalid (according to the ASPRS LAS file format specification) points.
	118	This switch should only be required in a few special circumstances.
	119
	120	Eliminate ground points
	121	~~~~~~~~~~~~~~~~~~~~~~~
	122
	123	::
	124
	125	$ las2las --input in.las --output out.las --eliminate_class 2
	126
	127	removes points with that have a classification of 2. Points with a
	128	classification of 2 are conventionally called ground points, but that convention
	129	may not be followed for older LAS 1.0 files.
	130
	131	Convert to 1.1
	132	~~~~~~~~~~~~~~~~~~~~~~
	133
	134	::
	135
	136	$ las2las --input in.las --output out.las --format 1.1
	137
	138	converts the in.las file to a 1.1-formatted file. For the most part, this
	139	conversion is "in name only." For example,
	140
	141
	142
87	143
88	144	Usage
…	…
101	157	las2las -i in.las -last_only -eliminate_intensity_below 2000 -olas > out.las
102	158	las2las -h
	159
	160	.. _`LAStools`: http://www.cs.unc.edu/~isenburg/lastools/

Context Navigation

Changeset 835

Legend:

trunk/Makefile.am

trunk/configure.ac

trunk/doc

trunk/doc/las2las.txt

Download in other formats: