[Liblas-devel] LASzip versus LT compressor
Michael P. Gerlek
mpg at flaxen.com
Wed Apr 27 12:07:47 EDT 2011
Nice - good work, Martin!
-mpg
From: Martin Isenburg [mailto:martin.isenburg at gmail.com]
Sent: Wednesday, April 27, 2011 8:55 AM
To: mpg at flaxen.com
Cc: liblas-devel at lists.osgeo.org
Subject: Re: [Liblas-devel] LASzip versus LT compressor
hi,
On Wed, Apr 27, 2011 at 8:28 AM, Michael P. Gerlek <mpg at flaxen.com> wrote:
Martin, can you give the data below in terms of compression ratio against
the original file sizes?
sure.
SID LAZ file_name original_file_size (MB)
3.1 5.9 autzen-colorized-1.2-3.las 345
2.8 7.0 Dallas.las 100
6.9 7.2 GrassLakeSmall.las 118
3.3 8.3 IowaDNR-CloudPeakSoft-1.0-UTM15N.las 156
6.5 7.4 LAS12_Sample_withRGB_QT_Modeler.las 95
4.3 4.6 LASFile_1.las 46
4.5 4.8 LASFile_2.las 42
4.2 4.6 LASFile_3.las 16
4.5 4.9 LASFile_4.las 46
4.4 4.7 LDR030828_212242_0.las 57
4.5 4.8 LDR030828_213023_0.las 56
4.3 4.6 LDR030828_213450_0.las 51
2.8 5.2 LDR091111_181233_1.las 52
2.8 5.3 LDR091111_182803_1.las 52
2.8 5.1 Ldr100402_220229_1.las 1781
6.1 6.5 Lincoln.las 177
4.0 3.8 line_27007_dd.las 103
6.3 8.3 MARS_Sample_Filtered_LiDAR.las 156
2.8 5.2 merrick_vertical_1.2.las 52
12.9 12.2 MountStHelensNov202004.las 110
6.4 6.6 MountStHelensOct42004.las 129
3.1 3.3 ncwc000008.las 60
6.5 6.8 PalmBeachPreHurricane.las 49
8.0 8.6 radiohead_data1.las 397
8.0 8.7 radiohead_data2.las 433
3.4 7.9 S1C1_strip021.las 75
3.3 9.1 SerpentMoundModelLASData.las 87
2.8 5.8 Tetons.las 100
2.9 5.3 USACE_Merrick_lots_of_VLRs.las 96
9.7 10.5 xyzrgb_manuscript.las 53
Also, are you willing to report the timing data?
for the 1.7 GB file it took LASzip 1:33 min to encode and 1:35 min to
decode. it took the LT compressor 18:26 min to encode and 4:46 min to
decode. your own mpg will vary depending on disk and compressor speeds ...
cheers,
martin @lastools
From: liblas-devel-bounces at lists.osgeo.org
[mailto:liblas-devel-bounces at lists.osgeo.org] On Behalf Of Martin Isenburg
Sent: Wednesday, April 27, 2011 8:12 AM
To: liblas-devel at lists.osgeo.org
Subject: [Liblas-devel] LASzip versus LT compressor
Hello,
People sometimes ask me how LASzip compares to the LIDAR compressor from
Lizard Tech and I usually refer them to Michael's email (see below). Because
his benchmarking was wrong on one model, namely MG4 does not outperform
LASzip on 2398_400.las, i did my own experiments that suggest that LASzip
compresses about 35% better and is faster.
A set of 27 LAS files (see below for a listing) compresses to 403 MB with
LASzip and to 610 MB with the LIDAR compressor from Lizard Tech.
A 1.7GB LAS file of a flight swath (see below for the details) compresses to
352 MB with LASzip and to 648 MB with the LIDAR compressor from Lizard Tech.
LASzip encoding is about 10 times faster. LASzip decoding is about 3 times
faster. timings measurements included all disk I/O from compressed file to
uncompressed file (and vice-versa) using two separate drives. disclaimer:
the LASzip compressor is tuned for LAS files that contain LIDAR in
acquisition order.
Cheers,
martin @lastools
the list of 27 LAS files. the first number is the compressed file size in
bytes for the LIDAR Compressor of Lizardtech. the second number is the
compressed file size in bytes for LASzip. all files can be found here
http://liblas.org/samples except "Dallas.las" and "Tetons.las" which are
here: http://bin.us.lizardtech.com/lidar/LT_LiDAR_Sample_Data.zip
115,857,121 61,809,700 autzen-colorized-1.2-3.las
37,462,947 14,881,473 Dallas.las
18,035,893 17,128,065 GrassLakeSmall.las
48,947,417 19,621,507 IowaDNR-CloudPeakSoft-1.0-UTM15N.las
15,248,628 13,382,538 LAS12_Sample_withRGB_QT_Modeler.las
11,222,840 10,444,300 LASFile_1.las
9,805,767 9,154,780 LASFile_2.las
3,966,869 3,665,433 LASFile_3.las
10,691,410 9,940,731 LASFile_4.las
13,522,405 12,672,774 LDR030828_212242_0.las
13,058,811 12,157,072 LDR030828_213023_0.las
12,244,190 11,502,895 LDR030828_213450_0.las
19,820,246 10,414,626 LDR091111_181233_1.las
19,424,894 10,193,907 LDR091111_182803_1.las
30,451,604 28,680,682 Lincoln.las
27,076,520 28,593,056 line_27007_dd.las
25,753,118 19,594,207 MARS_Sample_Filtered_LiDAR.las
19,820,246 10,414,626 merrick_vertical_1.2.las
8,943,713 9,493,209 MountStHelensNov202004.las
20,937,807 20,337,536 MountStHelensOct42004.las
20,386,038 19,036,134 ncwc000008.las
7,900,248 7,539,341 PalmBeachPreHurricane.las
22,831,603 9,920,385 S1C1_strip021.las
28,006,302 10,036,738 SerpentMoundModelLASData.las
37,216,167 18,169,153 Tetons.las
34,980,891 18,961,597 USACE_Merrick_lots_of_VLRs.las
5,756,508 5,351,794 xyzrgb_manuscript.las
the lasinfo details of the 1.7GB LAS file containing one swath
lasinfo Ldr100402_220229_1.laz
reporting all LAS header entries:
file signature: 'LASF'
file source ID: 0
reserved (global_encoding):0
project ID GUID data 1-4: 0 0 0 ''
version major.minor: 1.0
system identifier: 'ALSXX'
generating software: 'ALSXX_PP V2.69 BUILD#7 BETA'
file creation day/year: 92/2010
header size 227
offset to point data 5697
number var. length records 4
point data format 1
point data record length 28
number of point records 66705904
number of points by return 58445315 6743224 1404140 113225 0
scale factor x y z 0.001 0.001 0.001
offset x y z 13000000 0 0
min x y z 12991192.425 588397.501 611.122
max x y z 13142242.349 594146.283 3032.417
variable length header record 1 of 4:
reserved 43707
user ID 'LeicaGeo'
record ID 1001
length after header 5120
description ''
variable length header record 2 of 4:
reserved 43707
user ID 'LeicaGeo'
record ID 1002
length after header 22
description 'MissionInfo'
variable length header record 3 of 4:
reserved 43707
user ID 'LeicaGeo'
record ID 1003
length after header 54
description 'UserInputs'
variable length header record 4 of 4:
reserved 43707
user ID 'LASF_Projection'
record ID 34735
length after header 56
description 'Projection Info'
GeoKeyDirectoryTag version 1.1.0 number of keys 6
key 1024 tiff_tag_location 0 count 1 value_offset 1 -
GTModelTypeGeoKey: ModelTypeProjected
key 1025 tiff_tag_location 0 count 1 value_offset 2 -
GTRasterTypeGeoKey: RasterPixelIsPoint
key 3076 tiff_tag_location 0 count 1 value_offset 26990 -
ProjLinearUnitsGeoKey: look-up for 26990 not implemented
key 2052 tiff_tag_location 0 count 1 value_offset 9002 -
GeogLinearUnitsGeoKey: Linear_Foot
key 4096 tiff_tag_location 0 count 1 value_offset 5103 -
VerticalCSTypeGeoKey: VertCS_North_American_Vertical_Datum_1988
key 4099 tiff_tag_location 0 count 1 value_offset 9002 -
VerticalUnitsGeoKey: Linear_Foot
the header is followed by 2 user-defined bytes
LASzip compression (version 1.0r0 c1): POINT10 1 GPSTIME11 1
reporting minimum and maximum for all LAS point record entries ...
x -8807574 142242349
y 588397501 594146283
z 611122 3032417
intensity 0 255
edge_of_flight_line 0 0
scan_direction_flag 0 1
number_of_returns_of_given_pulse 1 4
return_number 1 4
classification 1 1
scan_angle_rank -26 31
user_data 161 255
point_source_ID 161 511
gps_time 511349.016753 512063.402540
overview over number of returns of given pulse: 51686151 10678566 3886669
454518 0 0 0
histogram of classification of points:
66705904 Unclassified (1)
----------------------------------------------------------------------------
----------
michael's email (the graphs he mentions can be found in the archive)
http://lists.osgeo.org/pipermail/liblas-devel/2011-February/001199.html
On Fri, Feb 4, 2011 at 3:21 PM, Michael Rosen <mrosen at lizardtech.com> wrote:
Here's the summary of some LT-internal (I guess not so internal now.)
benchmarking. Highlights:
- I can't really draw any conclusions about relative compression
sizes: 2398_400 favors MG4 2:1, HGAC_Extract and AutZen favor LAZ 2:1,
MtStHelens is a wash,
- WRT extraction time, for smaller files, the MG4's computational
overhead (*) favors LAZ for all but the smallest extractions
- For larger files, the "break even" point is much further to the
right.
- For larger files, with very small extractions, the built-in index
of MG4 allows faster extractions than raw (unindexed) LAS.
The methodology here was to run "las2las" as shown before cropping out
increasingly large rectangles (at full resolution)
I compared this with the same extraction from MG4 using a command line tool
(internal) but this time, writing the output to a las file.
I spot checked that the number of points written in all three cases was the
same.
(*) Note that the title on the graphs is not quite right. It's not "Decode
Time" but "Decode Time plus LAS Write Time" vs Scene Size. There is some
speculation (based on what we were observing when omitting the output) that
LT's LAS Writer is unusually slow. It's using the liblas v1.2 writer . so
some here may have well-informed opinions on this.
Here is some raw data and some graphs:
01/28/2011 03:50 PM 61,301,311 2398_400.las
01/28/2011 04:28 PM 8,906,275 2398_400.laz
01/28/2011 04:25 PM 4,650,992 2398_400.sid
01/28/2011 04:03 PM 362,213,959 autzen-colorized-1.2-3.las
01/28/2011 04:28 PM 61,809,700 autzen-colorized-1.2-3.laz
01/28/2011 04:27 PM 115,857,121 autzen-colorized-1.2-3.sid
01/28/2011 03:59 PM 123,876,781 Grass Lake Small.las
01/28/2011 04:29 PM 17,128,065 Grass Lake Small.laz
01/28/2011 04:25 PM 18,035,893 Grass Lake Small.sid
02/02/2011 08:18 AM 711,065,603 HGAC_Extract.las
02/02/2011 08:23 AM 151,159,393 HGAC_Extract.laz
02/02/2011 08:29 AM 269,491,108 HGAC_Extract.sid
01/28/2011 03:50 PM 34,065,751 hobu.las
01/28/2011 04:29 PM 7,732,878 hobu.laz
01/28/2011 04:24 PM 9,301,431 hobu.sid
01/28/2011 04:00 PM 185,565,975 Lincoln.las
01/28/2011 04:29 PM 28,680,682 Lincoln.laz
01/28/2011 04:25 PM 30,451,604 Lincoln.sid
01/28/2011 03:58 PM 107,603,879 line_27007.las
01/28/2011 04:30 PM 22,269,252 line_27007.laz
01/28/2011 04:25 PM 24,588,596 line_27007.sid
01/28/2011 03:58 PM 115,737,877 MtStHelens.las
01/28/2011 04:30 PM 9,493,209 MtStHelens.laz
01/28/2011 04:24 PM 8,943,713 MtStHelens.sid
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