Extracting waveform data from WDP files
243 views
Skip to first unread message
Charles Toth
Aug 15, 2020, 5:17:12 PM8/15/20
to PulseWaves - no pulse left behind
Hi,
This could be a naive question, as I have done practically nothing with waveforms for about 6-8 years; back then, I used the Riegl library. Now I got a sizable block of waveform data in WDP format and I would like to extract the waveform measurements. I have the matching LAS file, but not info on the relationship. My understanding is that LAS has the reference/pointer to the waveform data stored in the WDP file; obviously, it is an assumption from my side. Running pulseview.exe creates an error message, so no luck. My question: what is the easiest way to extract the waveform vectors from the WDP files? Also, the definition of the WDP format would be a step forward. Any help is greatly appreciated.
Thanks a lot,
--charles
Martin Isenburg
Aug 16, 2020, 9:04:23 AM8/16/20
to PulseWaves - no pulse left behind
Hello Charles,
could you run your LAS / WDP combo files through both lasinfo and pulseinfo and share the resulting reports in this group?
lasinfo -i lidar.las -o lidar_lasinfo.txt
lasinfo -i lidar.las -o lidar_lasinfo.txt
pulseinfo -i lidar.las -o lidar_pulseinfo.txt
Thank you,
Martin
--
--
Post to "PulseWaves" by email to pulse...@googlegroups.com
Unsubscribe by email to pulsewaves+...@googlegroups.com
Visit this group's message archives at http://pulsewaves.org
---
You received this message because you are subscribed to the Google Groups "PulseWaves - no pulse left behind" group.
To unsubscribe from this group and stop receiving emails from it, send an email to pulsewaves+...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/pulsewaves/93803d00-beab-4294-a21d-f17544449d0cn%40googlegroups.com.
Charles Toth
Aug 16, 2020, 7:00:39 PM8/16/20
to pulse...@googlegroups.com
Hi Martin,
Thanks a lot for the prompt reply. I have tried to run both commands, and recognized that my installation, PulseWaveDLL.ZIP is incomplete, as certain executables are missing. pulseinfo created the following messages:
WARNING: number of samples for wave packet descr 21 is zero
WARNING: temporal spacing for wave packet descr 21 is zero
ERROR: file 'ch1.las' contains points of type 9 without waveforms
ERROR: cannot open pulsereaderlas with file name 'ch1.las'
ERROR: cannot open pulsereader
WARNING: temporal spacing for wave packet descr 21 is zero
ERROR: file 'ch1.las' contains points of type 9 without waveforms
ERROR: cannot open pulsereaderlas with file name 'ch1.las'
ERROR: cannot open pulsereader
lasinfo is missing, so once it is installed as well as the other missing ones, i guess, i can provide the proper response.
Thanks again!
|
--charlesYou received this message because you are subscribed to a topic in the Google Groups "PulseWaves - no pulse left behind" group.
To unsubscribe from this topic, visit https://groups.google.com/d/topic/pulsewaves/Lbtjxeov-LY/unsubscribe.
To unsubscribe from this group and all its topics, send an email to pulsewaves+...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/pulsewaves/CABSWR-FxfZdXOneT%2Bzygfcjf3s1rS42MBs3UMYnLOk-cmjR9%3DA%40mail.gmail.com.
Martin Isenburg
Aug 16, 2020, 10:35:15 PM8/16/20
to PulseWaves - no pulse left behind
You will need to also download LAStools.zip to get the lasinfo.exe tool.
You should get a recent LAStools version (such as 200813 or newer) which you can download here:
http://lastools.org/download/LAStools.zip
http://lascloud.com/download/LAStools.zip
http://lastools.github.io/download/LAStools.zip
http://lastools.org/download
http://lascloud.com/download
http://lastools.github.io/download
You can see what new features or tools are available and what bugs were fixed in the newest LAStools version at
http://lastools.org/download/CHANGES.txt
You should get a recent LAStools version (such as 200813 or newer) which you can download here:
http://lastools.org/download/LAStools.zip
http://lascloud.com/download/LAStools.zip
http://lastools.github.io/download/LAStools.zip
http://lastools.org/download
http://lascloud.com/download
http://lastools.github.io/download
You can see what new features or tools are available and what bugs were fixed in the newest LAStools version at
http://lastools.org/download/CHANGES.txt
To view this discussion on the web visit https://groups.google.com/d/msgid/pulsewaves/CAPwxVVppip1_R2aUPcMxbDr4PykwYEdQ7Li54zc%3Dv_Pwxhtc8Q%40mail.gmail.com.
Charles Toth
Aug 17, 2020, 4:05:00 PM8/17/20
to PulseWaves - no pulse left behind
Hi Martin,
Thanks again for your continued support. After installing LASTools, the "lasinfo" runs, and the output file is included below. For the pulseinfo, it seems that some executables are still missing; at least, they are not part of the ZIP files.
Many thanks again,
--charles
____________________________________________________________________________
lasinfo (200813) report for 'ch1.las'
reporting all LAS header entries:
file signature: 'LASF'
file source ID: 1
global_encoding: 21
project ID GUID data 1-4: 00000000-0000-0000-0000-000000000000
version major.minor: 1.4
system identifier: 'EXTRACTION'
generating software: 'RiPROCESS 1.8.7'
file creation day/year: 212/2020
header size: 375
offset to point data: 3714
number var. length records: 25
point data format: 9
point data record length: 59
number of point records: 0
number of points by return: 0 0 0 0 0
scale factor x y z: 0.001 0.001 0.001
offset x y z: 2788993 1382405 7751
min x y z: 2788894.490 1331905.210 7129.380
max x y z: 2802729.780 1382404.770 8266.760
start of waveform data packet record: 0
start of first extended variable length record: 0
number of extended_variable length records: 0
extended number of point records: 149227481
extended number of points by return: 138222082 4859681 2909903 1778702 909251 373783 127174 36067 8525 1791 387 93 38 3 1
variable length header record 1 of 25:
reserved 43707
user ID 'LASF_Projection'
record ID 34735
length after header 216
description 'GeoKeyDirectoryTag (mandatory)'
GeoKeyDirectoryTag version 1.1.0 number of keys 26
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 1026 tiff_tag_location 34737 count 39 value_offset 0 - GTCitationGeoKey: NAD83 / Colorado South / G12BUS (ftUS)
key 2048 tiff_tag_location 0 count 1 value_offset 32767 - GeographicTypeGeoKey: user-defined
key 2049 tiff_tag_location 34737 count 6 value_offset 78 - GeogCitationGeoKey: NAD83
key 2050 tiff_tag_location 0 count 1 value_offset 32767 - GeogGeodeticDatumGeoKey: user-defined
key 2051 tiff_tag_location 0 count 1 value_offset 32767 - GeogPrimeMeridianGeoKey: user-defined
key 2052 tiff_tag_location 0 count 1 value_offset 9003 - GeogLinearUnitsGeoKey: Linear_Foot_US_Survey
key 2054 tiff_tag_location 0 count 1 value_offset 9102 - GeogAngularUnitsGeoKey: Angular_Degree
key 2056 tiff_tag_location 0 count 1 value_offset 32767 - GeogEllipsoidGeoKey: user-defined
key 2057 tiff_tag_location 34736 count 1 value_offset 0 - GeogSemiMajorAxisGeoKey: 6378137
key 2059 tiff_tag_location 34736 count 1 value_offset 1 - GeogInvFlatteningGeoKey: 298.2572221
key 2060 tiff_tag_location 0 count 1 value_offset 9102 - GeogAzimuthUnitsGeoKey: Angular_Degree
key 2061 tiff_tag_location 34736 count 1 value_offset 2 - GeogPrimeMeridianLongGeoKey: 0
key 3072 tiff_tag_location 0 count 1 value_offset 32767 - ProjectedCSTypeGeoKey: user-defined
key 3073 tiff_tag_location 34737 count 39 value_offset 39 - PCSCitationGeoKey: NAD83 / Colorado South / G12BUS (ftUS)
key 3074 tiff_tag_location 0 count 1 value_offset 32767 - ProjectionGeoKey: user-defined
key 3075 tiff_tag_location 0 count 1 value_offset 8 - ProjCoordTransGeoKey: CT_LambertConfConic_2SP
key 3076 tiff_tag_location 0 count 1 value_offset 9003 - ProjLinearUnitsGeoKey: Linear_Foot_US_Survey
key 3078 tiff_tag_location 34736 count 1 value_offset 3 - ProjStdParallel1GeoKey: 38.43333333
key 3079 tiff_tag_location 34736 count 1 value_offset 4 - ProjStdParallel2GeoKey: 37.23333333
key 3084 tiff_tag_location 34736 count 1 value_offset 6 - ProjFalseOriginLongGeoKey: -105.5
key 3085 tiff_tag_location 34736 count 1 value_offset 5 - ProjFalseOriginLatGeoKey: 36.66666667
key 3086 tiff_tag_location 34736 count 1 value_offset 7 - ProjFalseOriginEastingGeoKey: 3000000
key 3087 tiff_tag_location 34736 count 1 value_offset 8 - ProjFalseOriginNorthingGeoKey: 1000000
key 4099 tiff_tag_location 0 count 1 value_offset 9003 - VerticalUnitsGeoKey: Linear_Foot_US_Survey
variable length header record 2 of 25:
reserved 43707
user ID 'LASF_Spec'
record ID 100
length after header 26
description 'WPD#1'
index 1 bits/sample 16 compression 0 samples 48 temporal 1005 gain 1, offset 0
variable length header record 3 of 25:
reserved 43707
user ID 'LASF_Spec'
record ID 101
length after header 26
description 'WPD#2'
index 2 bits/sample 16 compression 0 samples 32 temporal 1005 gain 1, offset 0
variable length header record 4 of 25:
reserved 43707
user ID 'LASF_Spec'
record ID 102
length after header 26
description 'WPD#3'
index 3 bits/sample 16 compression 0 samples 40 temporal 1005 gain 1, offset 0
variable length header record 5 of 25:
reserved 43707
user ID 'LASF_Spec'
record ID 103
length after header 26
description 'WPD#4'
index 4 bits/sample 16 compression 0 samples 72 temporal 1005 gain 1, offset 0
variable length header record 6 of 25:
reserved 43707
user ID 'LASF_Spec'
record ID 104
length after header 26
description 'WPD#5'
index 5 bits/sample 16 compression 0 samples 56 temporal 1005 gain 1, offset 0
variable length header record 7 of 25:
reserved 43707
user ID 'LASF_Spec'
record ID 105
length after header 26
description 'WPD#6'
index 6 bits/sample 16 compression 0 samples 64 temporal 1005 gain 1, offset 0
variable length header record 8 of 25:
reserved 43707
user ID 'LASF_Spec'
record ID 106
length after header 26
description 'WPD#7'
index 7 bits/sample 16 compression 0 samples 88 temporal 1005 gain 1, offset 0
variable length header record 9 of 25:
reserved 43707
user ID 'LASF_Spec'
record ID 107
length after header 26
description 'WPD#8'
index 8 bits/sample 16 compression 0 samples 80 temporal 1005 gain 1, offset 0
variable length header record 10 of 25:
reserved 43707
user ID 'LASF_Spec'
record ID 108
length after header 26
description 'WPD#9'
index 9 bits/sample 16 compression 0 samples 96 temporal 1005 gain 1, offset 0
variable length header record 11 of 25:
reserved 43707
user ID 'LASF_Spec'
record ID 109
length after header 26
description 'WPD#10'
index 10 bits/sample 16 compression 0 samples 104 temporal 1005 gain 1, offset 0
variable length header record 12 of 25:
reserved 43707
user ID 'LASF_Spec'
record ID 110
length after header 26
description 'WPD#11'
index 11 bits/sample 16 compression 0 samples 112 temporal 1005 gain 1, offset 0
variable length header record 13 of 25:
reserved 43707
user ID 'LASF_Spec'
record ID 111
length after header 26
description 'WPD#12'
index 12 bits/sample 16 compression 0 samples 120 temporal 1005 gain 1, offset 0
variable length header record 14 of 25:
reserved 43707
user ID 'LASF_Spec'
record ID 112
length after header 26
description 'WPD#13'
index 13 bits/sample 16 compression 0 samples 128 temporal 1005 gain 1, offset 0
variable length header record 15 of 25:
reserved 43707
user ID 'LASF_Spec'
record ID 113
length after header 26
description 'WPD#14'
index 14 bits/sample 16 compression 0 samples 136 temporal 1005 gain 1, offset 0
variable length header record 16 of 25:
reserved 43707
user ID 'LASF_Spec'
record ID 114
length after header 26
description 'WPD#15'
index 15 bits/sample 16 compression 0 samples 144 temporal 1005 gain 1, offset 0
variable length header record 17 of 25:
reserved 43707
user ID 'LASF_Spec'
record ID 115
length after header 26
description 'WPD#16'
index 16 bits/sample 16 compression 0 samples 152 temporal 1005 gain 1, offset 0
variable length header record 18 of 25:
reserved 43707
user ID 'LASF_Spec'
record ID 116
length after header 26
description 'WPD#17'
index 17 bits/sample 16 compression 0 samples 160 temporal 1005 gain 1, offset 0
variable length header record 19 of 25:
reserved 43707
user ID 'LASF_Spec'
record ID 117
length after header 26
description 'WPD#18'
index 18 bits/sample 16 compression 0 samples 176 temporal 1005 gain 1, offset 0
variable length header record 20 of 25:
reserved 43707
user ID 'LASF_Spec'
record ID 118
length after header 26
description 'WPD#19'
index 19 bits/sample 16 compression 0 samples 168 temporal 1005 gain 1, offset 0
variable length header record 21 of 25:
reserved 43707
user ID 'LASF_Spec'
record ID 119
length after header 26
description 'WPD#20'
index 20 bits/sample 16 compression 0 samples 184 temporal 1005 gain 1, offset 0
variable length header record 22 of 25:
reserved 43707
user ID 'LASF_Spec'
record ID 120
length after header 26
description 'WPD#21'
index 21 bits/sample 16 compression 0 samples 0 temporal 0 gain 1, offset 0
variable length header record 23 of 25:
reserved 43707
user ID 'LASF_Projection'
record ID 34736
length after header 72
description 'GeoDoubleParamsTag (optional)'
GeoDoubleParamsTag (number of doubles 9)
6.37814e+006 298.257 0 38.4333 37.2333 36.6667 -105.5 3e+006 1e+006
variable length header record 24 of 25:
reserved 43707
user ID 'LASF_Projection'
record ID 34737
length after header 84
description 'GeoASCIIParamsTag (optional)'
GeoAsciiParamsTag (number of characters 84)
NAD83 / Colorado South / G12BUS (ftUS)|NAD83 / Colorado South / G12BUS (ftUS)|NAD83|
variable length header record 25 of 25:
reserved 43707
user ID 'LASF_Projection'
record ID 2112
length after header 1071
description 'OGC COORDINATE SYSTEM WKT'
WKT OGC COORDINATE SYSTEM:
COMPD_CS["NAD83 / Colorado South / G12BUS (ftUS)",PROJCS["NAD83 / Colorado South / G12BUS (ftUS)",GEOGCS["NAD83 / Colorado South / G12BUS (ftUS)",DATUM["NAD83",SPHEROID["GRS 1980",6378137.000,298.257222101,AUTHORITY["EPSG","7019"]],AUTHORITY["EPSG","6269"]],PRIMEM["Greenwich",0.0000000000000000,AUTHORITY["EPSG","8901"]],UNIT["Degree",0.01745329251994329547,AUTHORITY["EPSG","9102"]],AUTHORITY["EPSG","0"]],PROJECTION["Lambert_Conformal_Conic_2SP",AUTHORITY["EPSG","9802"]],PARAMETER["standard_parallel_1",38.4333333333333229],PARAMETER["standard_parallel_2",37.2333333333333343],PARAMETER["latitude_of_origin",36.6666666666666643],PARAMETER["central_meridian",-105.5000000000000000],PARAMETER["false_easting",3000000.000],PARAMETER["false_northing",1000000.000],UNIT["US survey foot",0.30480060960121918567,AUTHORITY["EPSG","9003"]],AXIS["Easting",EAST],AXIS["Northing",NORTH],AUTHORITY["EPSG","0"]],VERT_CS["Orthometric Heights",VERT_DATUM["G12BUS",2005,AUTHORITY["EPSG","0"]],UNIT["US survey foot",0.30480060960121918567,AUTHORITY["EPSG","9003"]],AXIS["Height",UP]]]
reporting minimum and maximum for all LAS point record entries ...
X -98501 13736773
Y -50499783 -236
Z -621611 515754
intensity 0 65535
return_number 1 7
number_of_returns 1 7
edge_of_flight_line 0 1
scan_direction_flag 0 0
classification 0 0
scan_angle_rank -43 35
user_data 0 0
point_source_ID 1 1
gps_time 272227587.504771 272227797.583708
Wavepacket Index 0 20
Offset 0 13428539180
Size 0 368
Location -100887 68508
Xt -0.000100831 8.59588e-005
Yt -3.90028e-005 2.12981e-005
Zt 0 0.000149856
extended_return_number 1 15
extended_number_of_returns 1 15
extended_classification 0 255
extended_scan_angle -7167 5833
extended_scanner_channel 0 0
number of first returns: 138222082
number of intermediate returns: 6145718
number of last returns: 138222082
number of single returns: 133362401
overview over extended number of returns of given pulse: 133362401 3899556 3393603 3477804 2677340 1479654 637749 220336 60606 14040 3234 660 455 28 15
histogram of classification of points:
149190383 never classified (0)
+-> flagged as synthetic: 53558
+---> 53558 of those are never classified (0)
histogram of extended classification of points:
37098 extended classification (255)
Charles Toth
Aug 26, 2020, 10:20:54 AM8/26/20
to PulseWaves - no pulse left behind
Folks,
I still cannot find the "pulsereader" and "pulsereaderlas" executables. Any suggestions on what distribution module contains it?
Thanks a lot,
--charles
Martin Isenburg
Aug 26, 2020, 10:32:40 AM8/26/20
to PulseWaves - no pulse left behind
Hello,
sorry for the late reply but these are testing times - especially given that in addition to the pandemic response I am taking down a (suspected) money laundering operation in this little church town (who attacked my house when totally drunk) and have to deal with the fall-out of the defamation, slander and libel by the US DoI / BLM.
https://www.linkedin.com/feed/update/urn:li:activity:6658937256344113152/
https://groups.google.com/g/lastools/c/H5wjOdfynQA
https://www.linkedin.com/feed/update/urn:li:activity:6658937256344113152/
https://groups.google.com/g/lastools/c/H5wjOdfynQA
You might be able - as a quick fix - to access the waveforms with las2txt from LAStools.
las2txt -i in.las -parse xyzirntWV -o verbose.txt
http://rapidlasso.com/las2txt
http://lastools.org/download/las2txt_README.txt
Regards,
http://rapidlasso.com/las2txt
http://lastools.org/download/las2txt_README.txt
Regards,
Martin
To view this discussion on the web visit https://groups.google.com/d/msgid/pulsewaves/28324d42-b894-4158-90f6-77cef1207769n%40googlegroups.com.
Charles Toth
Aug 29, 2020, 10:29:35 AM8/29/20
to PulseWaves - no pulse left behind
Hi Martin,
Thanks so much for your advice! It’s a major step forward, as finally I could see a waveform. Thanks a lot!
Of course, as always, there are still a few questions. I read the README file, and my interpretation is:
· “xyz” is obvious.
· “I” is intensity, which I guess is for the first return, or for multiple returns, it’s for the actual return. I guess, each record comes with the same waveform, right?
· “r” is the number of this return; I guess the index number for multiple returns, right? Otherwise it is 1.
· “n” number of returns for given pulse. So “r” is between 1 and “n”, right?
· “t” GPS time, which looks fine; for my data, it looks like the pulse rate was 1 MHz.
· “VW” for waveform data.
Based on looking at first few records, I see the logic for the first six tokens. After that there are 57 items, and the pattern is:
1. “1” for all the records I have looked at.
2. One integer in the range of hundreds to thousands.
3. Then come a “96” for all the records I have looked at. My guess is that 96 could be the number of the waveform samples, though it is not case here.
4. Then comes a large negative integer number
5. Next, there are three floating point numbers, very small values
6. Then two numbers “16 48” I guess 48 is the number of samples.
7. And finally, 48 samples. It seems to me short. Say, for 1 ns sampling rate, it would mean 12 m vertical range, which is not much for an average forest, etc.
So the interpretation of these items, especially the first five, are the uncertain points.
Many thanks again,
--charles
PS: Some samples from my data
las2txt -i in.las -parse xyzirntWV -o verbose.txt
File Size is 45828.02792739868 MB
2788993.419 1382404.764 2788993.419 50090 1 1 272227587.504771 1 60 96 -88664 7.06448e-05 -9.35369e-07 0.000132156 16 48 166 165 163 163 165 166 168 177 220 366 618 848 921 824 637 453 321 246 206 182 173 169 167 165 160 155 156 161 165 166 164 163 160 162 165 165 163 159 156 157 162 168 172 168 168 165 162 160
2788994.892 1382404.692 2788994.892 49347 1 1 272227587.504772 1 156 96 -87270 7.0607e-05 -9.33178e-07 0.000132176 16 48 159 161 166 168 165 164 163 161 163 183 283 492 724 857 828 678 495 351 260 212 189 178 173 167 162 158 158 162 166 166 165 163 160 161 161 163 159 156 152 153 152 154 155 156 159 166 168 166
2788996.326 1382404.621 2788996.326 50789 1 1 272227587.504773 1 252 96 -85303 7.05693e-05 -9.30988e-07 0.000132196 16 48 159 161 162 165 163 157 159 157 157 161 164 194 322 573 831 964 920 747 546 384 287 233 199 181 171 167 163 164 165 166 160 162 169 168 166 166 165 163 159 158 157 157 153 159 162 165 160 157
...
2788997.715 1382404.563 2788997.715 49872 1 1 272227587.504774 1 348 96 -86799 7.05333e-05 -9.28901e-07 0.000132216 16 48 158 158 157 155 154 156 157 161 160 171 231 399 650 856 900 784 595 425 314 252 218 194 182 170 165 164 163 160 161 162 161 159 157 157 155 161 162 163 163 163 167 165 163 159 156 156 156 157
2789120.820 1382398.615 2789120.820 51554 1 1 272227587.504858 0 0 0 0 0 0 0 no_waveform
2789122.171 1382398.544 2789122.171 51576 1 1 272227587.504859 1 8316 96 -85029 6.72391e-05 -7.3889e-07 0.000133922 16 48 166 169 165 164 164 158 157 154 157 158 163 183 271 504 807 1013 1012 847 620 434 314 249 215 194 180 174 164 158 157 155 155 159 162 161 160 161 162 162 161 160 159 164 166 165 163 161 163 159
2789123.656 1382398.473 2789123.656 50112 1 1 272227587.504860 1 8412 96 -88246 6.7199e-05 -7.3659e-07 0.000133942 16 48 157 157 162 163 161 155 151 150 173 281 512 774 921 884 721 524 372 279 233 205 188 174 166 161 158 157 160 162 160 158 156 160 161 159 160 157 155 156 160 162 160 159 160 164 164 162 158 153
...
2789133.838 1382397.986 2789133.838 50549 1 1 272227587.504867 1 8988 96 -87274 6.69244e-05 -7.2084e-07 0.00013408 16 48 159 161 160 160 164 168 173 175 175 189 298 542 816 959 918 749 544 377 277 226 199 187 181 171 164 163 159 157 157 155 154 158 159 161 161 159 159 158 161 160 159 156 157 157 157 156 157 160
2789135.317 1382397.915 2789135.317 50811 1 1 272227587.504868 1 9084 96 -85367 6.68834e-05 -7.18485e-07 0.0001341 16 48 157 156 157 158 162 165 167 163 163 165 162 197 330 585 850 986 928 739 528 372 276 225 195 179 170 169 167 166 164 160 158 157 160 158 155 157 159 160 163 162 159 157 155 158 163 166 168 165
2789136.790 1382397.843 2789136.790 50396 1 1 272227587.504869 0 0 0 0 0 0 0 no_waveform
Number of Lines in the file is 149227481
Press any key to continue . . .
Martin Isenburg
Aug 29, 2020, 12:29:32 PM8/29/20
to PulseWaves - no pulse left behind
Hello Charles,
Regards,
I think 96 is the size of the waveform samples. If each is stored as a 2 byte integer then 48 samples x 2 bytes / sample = 96 bytes I once made this attached illustration and this is discussed in greater detail in this discussion thread:
https://groups.google.com/g/lasroom/c/g4VsXH3CRZo/m/df77U6S0RG4J
And it led to this additional clarification to the LAS specification.
https://groups.google.com/g/lasroom/c/g4VsXH3CRZo/m/df77U6S0RG4J
And it led to this additional clarification to the LAS specification.
And yes ... 48 is not enough to analyse interesting forests. The problem is that the digitizers try to minimize storage. I once had RIEGL change the RiAQUIRE settings such that the Q680i would ALWAYS store 400 samples for every shot starting just before the first return. I did that as part of this pro-bono campaign for WWF's TREEMAPS project that later failed (silently and I will expose that dishonest trust-eroding donation fraud by WWF Germany / Thailand someday).
I have a brief presentation / abstract on this somewhere.
Regards,
Marti
To view this discussion on the web visit https://groups.google.com/d/msgid/pulsewaves/6cd38b8f-9fbd-491d-a35b-c65ead9ef979n%40googlegroups.com.
Charles Toth
Aug 30, 2020, 8:42:44 AM8/30/20
to pulse...@googlegroups.com
Hi Martin,
Many thanks again, your prompt and constructive responses are appreciated!. I think you have helped a lot, and now I should be ready for real number crunching. BTW, I will also check with Riegl on the concern of short waveform sample length.
All the best,
--charles
|
You received this message because you are subscribed to a topic in the Google Groups "PulseWaves - no pulse left behind" group.
To unsubscribe from this topic, visit https://groups.google.com/d/topic/pulsewaves/Lbtjxeov-LY/unsubscribe.
To unsubscribe from this group and all its topics, send an email to pulsewaves+...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/pulsewaves/CABSWR-Eic-TQh%2B42wp3khNf1Eb9gtnFCMK7LBOufBn2SV_gysw%40mail.gmail.com.
Martin Isenburg
Aug 30, 2020, 9:00:18 AM8/30/20
to PulseWaves - no pulse left behind
Hello,
sure thing, Charles. We rogue scientists have to stick together ... (-;
The waveforms are so short because of the I/O bottleneck. This is a problem if you want the waveforms to detect near undetectable things. It needs a strong enough reflection (that may then become the first return) to turn on the storage of the waveform samples and it needs regular subsequent reflections (that may then become the second, third, fourth, ... returns) to keep storing the waveform. In my application the idea where we had 50 meter tropical canopy most of the "standard" settings only sampled the first 12, 18, 24 or 36 meters after the top canopy hit. Even if there would have been a faint ground hit to be recovered in complex post processing, we would not have gotten those samples off the device (out of the SDF files) because they would now have been stored. The manual override we did with "always digitize 400 samples no matter what" meant we could only operate the !680i at at 80 kHz shot rate, but I have waveforms digitized all the way through the entire canopy - even though most of it may be noise.
You should try to do a project in the TropiDry forests of Guanacaste so we can have a Happy Hour cocktail on the beach someday and you can meet my "laser chickens" ... (-;
Regards,
Martin
To view this discussion on the web visit https://groups.google.com/d/msgid/pulsewaves/CAPwxVVoL_0WpG6e%2BN%2BOANe1B8Rw4OdJ8MfcXY%3DjxHnj-NJPujA%40mail.gmail.com.
Reply all
Reply to author
Forward
0 new messages