using "overlap flag" of new LAS 1.4 point types

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Martin Isenburg

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May 16, 2015, 2:42:50 PM5/16/15
to LAStools - efficient command line tools for LIDAR processing
Hello,

the latest version of LAStools released today (150516) improves handling the new point types of LAS 1.4 that are now required for all  deliveries based on the newest USGS specifications. You can download the latest LAStools version from http://rapidlasso.com/LAStools

Here how to use the new "overlap flag" of the new LAS 1.4 points. Screengrabs for all lasview visualizations are attached. 

(1) if needed, convert your LiDAR tiles from LAS 1.2 to LAS 1.4

las2las -i tile12.laz ^
            -set_version 1.4 -set_point_type 6 ^
            -o tile14.las

(2) inspect the presence of properly populated flight line information stored in the point_source_IDs (if you do not have it you need to use in addition the new option 'recover_flightlines' in step (4).

lasview -i tile14.las ^
             -color_by_flightline

(3) inspect the presence of properly populated scan angles with this simple new trick

lasview -i tile14.las ^
            -bin_abs_scan_angle_into_point_source 5.0 ^
            -color_by_flightline

lasview -i tile14.las ^
            -bin_abs_scan_angle_into_point_source 3.0 ^
            -color_by_flightline

(3) flag the points in the overage that have the larger scan angles as overlap

lasoverage -i tile14.las ^
                  -flag_as_overlap ^
                  -odix _over

(4) inspect how the overlap flags were applied

lasview -i tile14_over.las ^
            -drop_overlap ^
            -color_by_flightline

lasview -i tile14_over.las ^
             -keep_overlap ^
             -color_by_flightline

(5) check how many points are flagged as overlap

lasinfo -i tile14_over.las 
[...]
  version major.minor:        1.4
  system identifier:          'LAStools (c) by rapidlasso GmbH'
  generating software:        'lasoverage (150516) commercial'
  file creation day/year:     114/2015
  header size:                375
  offset to point data:       377
  number var. length records: 0
  point data format:          6
  point data record length:   30
[...]
  extended number of point records: 2393815
  extended number of points by return: 2337870 37421 12839 4223 1165 244 53 0 0 0 0 0 0 0 0
[...]
  gps_time 110833707.644651 110834135.543584
  extended_number_of_returns      1      7
  extended_return_number          1      7
  extended_classification         3     10
  extended_scan_angle         -3333   2500
  extended_scanner_channel        0      0
overview over number of returns of given pulse: 2300313 49278 25844 12251 4612 1206 311
 +-> flagged as extended overlap: 436988

(6) use the overlap flags in DTM production

las2dem -i tile14_over.las ^
              -keep_class 2 8 ^
              -drop_overlap ^
              -step 0.5 ^
              -ocut 5 -odix _dtm -otif 

(7) compress and uncompress the LAS 1.4 files for efficient delivery / storage

laszip -i tile14_over.las -o tile14_final.laz
laszip -i tile14_final.laz -o tile14_final.las

(8) reassure yourself that compression - also for LAS 1.4 - is lossless

lasdiff -i tile14_over.las -i tile14_final.las

===================================================

Here are all the improvements in the new version:

16 May 2015 -- all LAStools: projections Albers Equal Area Conic and Earth Centered Earth Fixed
15 May 2015 -- lasclip: added '-flag_as_withheld' as an alternative to removing or reclassifying
15 May 2015 -- lasoverage: added option '-recover_flightlines' for missing point_source_IDs
14 May 2015 -- lasinfo: added a new option '-set_GUID F794F8A4-A23E-421E-A134-ACF7754E1C54'
10 May 2015 -- lasoverlap: new '-min_diff 0.2' with '-max_diff 0.5' for more focused error coloring
 3 May 2015 -- lastile: small fix sets file source ID to 0 when tiling many flightlines into tiles
 3 May 2015 -- las2las: improved up-conversion to LAS 1.4 via '-set_version 1.4 -point_type 6'
24 April 2015 -- las2txt: added 'k'eypoint and 'o'verlap flags as new parse string options
24 April 2015 -- lasoverage: added 'flag_as_overlap' for the new flag in the LAS 1.4 point types


Regards,

Martin @rapidlasso

--
http://rapidlasso.com - fast tools to 1.4 your LiDARs
lasoverage_step2_have_flightline.png
lasoverage_step3_have_scan_angle_5_degrees.png
lasoverage_step3_have_scan_angle_3_degrees.png
lasoverage_step5_drop_overlap.png
lasoverage_step5_keep_overlap.png

Susana Gonzalez

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May 26, 2015, 2:09:12 AM5/26/15
to last...@googlegroups.com

Hi Martin,

Could you check if will be possible to use the same steps bellow but using –odir?

I have tried it but I got the following message for las2las and lasoverage using the command line:

‘-odir’ is not recognized as an internal or external command, operable program or batch file.

Thanks

Susana

Martin Isenburg

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May 29, 2015, 1:01:00 PM5/29/15
to LAStools - efficient command line tools for LIDAR processing
Hello Susana,

looks to me like you are using a multi-line command but forgot to end an intermediate line with ^

las2las -i with_fluff\*.laz ^
            -rescale 0.01 0.01 0.01
            -odir without_fluff -olaz

instead of

las2las -i with_fluff\*.laz ^
            -rescale 0.01 0.01 0.01 ^
            -odir without_fluff -olaz

Regards,

Martin @rapidlasso

Reginald Argamosa

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Sep 15, 2015, 12:46:23 AM9/15/15
to LAStools - efficient tools for LiDAR processing
Hi Martin,

Point density is necessary for me because I can use those to compute different forestry parameters. However, i don't know how will to treat overlapping tiles since point density could be doubled in those tiles. Is there any way in LAStools to compute for the actual point density of the overlapping tiles?

Many thanks 

Regi 
 

Martin Isenburg

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Sep 19, 2015, 3:40:14 PM9/19/15
to LAStools - efficient command line tools for LIDAR processing
Hello,

not entirely sure what you are asking but for most of the different forestry metrics that can be computed with lascanopy the normalization for the density is automatically accounted for. You can, however, produce either a raster of counters or of densities using lasgrid. You have to decide whether you want an all-return count / density raster or a last-return density raster that is more or less equal to a pulse count / density raster.

lasgrid -i ..\data\fusa.laz ^
          -step 10 -counter_16bit ^
          -o fusa_counter_10m_all_return.asc

lasgrid -i ..\data\fusa.laz ^
          -step 10 -point_density_16bit ^
          -o fusa_density_10m_all_return.asc

lasgrid -i ..\data\fusa.laz ^
          -last_only ^
          -step 10 -counter_16bit ^
          -o fusa_counter_10m_last_return.asc

lasgrid -i ..\data\fusa.laz ^
          -last_only ^
          -step 10 -point_density_16bit ^
          -o fusa_density_10m_last_return.asc

>> more fusa_counter_10m_all_return.asc
ncols 25
nrows 25
xllcorner 277750.000000
yllcorner 6122250.000000
cellsize 10.000000
NODATA_value -9999
419 424 445 409 346 420 429 419 418 448 454 429 447 385 415 487 493 503 500 453 497 450 424 377 476
420 428 453 386 404 416 479 393 365 398 429 440 493 410 429 478 474 486 456 409 530 448 417 381 470
422 457 429 424 422 433 477 500 417 410 436 439 438 413 461 434 489 443 489 436 479 414 420 382 468
429 441 450 458 390 453 488 431 434 416 451 417 443 388 447 478 510 477 454 441 496 458 426 381 473
419 470 423 432 347 337 438 446 419 410 430 394 508 400 449 475 491 491 472 489 448 470 441 393 514
434 437 419 431 361 330 455 443 419 450 430 413 454 410 446 496 476 469 551 523 414 482 450 420 545
412 422 415 416 374 388 463 444 424 431 417 449 542 434 456 509 502 602 579 475 503 468 476 469 500
440 436 441 410 375 350 444 466 448 413 442 424 463 426 488 492 479 505 533 481 451 469 450 404 540
424 484 433 444 407 389 497 468 446 384 440 388 422 405 496 519 478 499 479 447 491 434 504 434 521
468 470 459 418 385 400 468 486 403 429 427 406 441 428 458 505 524 493 559 453 474 434 454 418 479
441 456 439 431 388 406 489 462 432 429 431 456 458 416 414 486 460 457 453 435 444 415 438 413 474
425 428 442 411 386 397 464 456 430 426 436 400 471 414 402 476 447 469 471 463 459 422 450 411 470
427 411 429 436 377 332 438 457 385 391 418 422 443 452 387 511 486 471 470 450 413 446 438 402 480
413 437 470 472 391 437 491 463 442 500 438 484 464 460 405 487 464 508 535 465 498 462 463 384 504
431 413 530 497 454 494 511 518 490 422 430 450 478 486 368 554 532 472 491 497 447 450 419 372 513
412 470 489 484 417 447 508 472 415 430 454 423 466 440 403 451 459 466 467 471 448 433 443 381 544
431 444 476 470 409 436 504 469 398 433 409 437 446 421 392 479 482 498 513 518 479 419 449 392 501
403 508 442 417 359 384 440 412 428 361 516 433 434 404 403 539 489 587 555 548 455 434 446 406 457
410 473 421 389 329 359 419 434 384 400 456 431 457 414 471 577 532 548 589 521 457 450 437 388 481
416 457 411 402 411 376 440 426 394 370 379 398 460 446 485 551 542 564 629 587 511 422 450 372 470
409 476 419 432 398 380 429 433 410 402 424 382 487 439 486 497 576 567 558 513 454 448 428 350 479
418 411 406 374 391 329 375 440 362 400 363 433 529 433 508 511 550 569 546 474 424 450 443 394 479
392 446 402 404 382 361 369 441 336 399 359 449 454 434 479 546 537 476 487 463 422 452 394 386 481
404 503 377 328 335 345 354 412 337 343 380 387 416 406 386 421 408 445 446 446 465 446 391 404 464
474 347 441 418 360 349 406 431 399 401 420 435 414 386 384 414 446 443 444 447 422 422 424 389 441

>> more fusa_density_10m_all_return.asc
ncols 25
nrows 25
xllcorner 277750.000000
yllcorner 6122250.000000
cellsize 10.000000
NODATA_value -9999.0
4.19 4.24 4.45 4.09 3.46 4.20 4.29 4.19 4.18 4.48 4.54 4.29 4.47 3.85 4.15 4.87 4.93 5.03 5.00 4.53 4.97 4.50 4.24 3.77 4.76
4.20 4.28 4.53 3.86 4.04 4.16 4.79 3.93 3.65 3.98 4.29 4.40 4.93 4.10 4.29 4.78 4.74 4.86 4.56 4.09 5.30 4.48 4.17 3.81 4.70
4.22 4.57 4.29 4.24 4.22 4.33 4.77 5.00 4.17 4.10 4.36 4.39 4.38 4.13 4.61 4.34 4.89 4.43 4.89 4.36 4.79 4.14 4.20 3.82 4.68
4.29 4.41 4.50 4.58 3.90 4.53 4.88 4.31 4.34 4.16 4.51 4.17 4.43 3.88 4.47 4.78 5.10 4.77 4.54 4.41 4.96 4.58 4.26 3.81 4.73
4.19 4.70 4.23 4.32 3.47 3.37 4.38 4.46 4.19 4.10 4.30 3.94 5.08 4.00 4.49 4.75 4.91 4.91 4.72 4.89 4.48 4.70 4.41 3.93 5.14
4.34 4.37 4.19 4.31 3.61 3.30 4.55 4.43 4.19 4.50 4.30 4.13 4.54 4.10 4.46 4.96 4.76 4.69 5.51 5.23 4.14 4.82 4.50 4.20 5.45
4.12 4.22 4.15 4.16 3.74 3.88 4.63 4.44 4.24 4.31 4.17 4.49 5.42 4.34 4.56 5.09 5.02 6.02 5.79 4.75 5.03 4.68 4.76 4.69 5.00
4.40 4.36 4.41 4.10 3.75 3.50 4.44 4.66 4.48 4.13 4.42 4.24 4.63 4.26 4.88 4.92 4.79 5.05 5.33 4.81 4.51 4.69 4.50 4.04 5.40
4.24 4.84 4.33 4.44 4.07 3.89 4.97 4.68 4.46 3.84 4.40 3.88 4.22 4.05 4.96 5.19 4.78 4.99 4.79 4.47 4.91 4.34 5.04 4.34 5.21
4.68 4.70 4.59 4.18 3.85 4.00 4.68 4.86 4.03 4.29 4.27 4.06 4.41 4.28 4.58 5.05 5.24 4.93 5.59 4.53 4.74 4.34 4.54 4.18 4.79
4.41 4.56 4.39 4.31 3.88 4.06 4.89 4.62 4.32 4.29 4.31 4.56 4.58 4.16 4.14 4.86 4.60 4.57 4.53 4.35 4.44 4.15 4.38 4.13 4.74
4.25 4.28 4.42 4.11 3.86 3.97 4.64 4.56 4.30 4.26 4.36 4.00 4.71 4.14 4.02 4.76 4.47 4.69 4.71 4.63 4.59 4.22 4.50 4.11 4.70
4.27 4.11 4.29 4.36 3.77 3.32 4.38 4.57 3.85 3.91 4.18 4.22 4.43 4.52 3.87 5.11 4.86 4.71 4.70 4.50 4.13 4.46 4.38 4.02 4.80
4.13 4.37 4.70 4.72 3.91 4.37 4.91 4.63 4.42 5.00 4.38 4.84 4.64 4.60 4.05 4.87 4.64 5.08 5.35 4.65 4.98 4.62 4.63 3.84 5.04
4.31 4.13 5.30 4.97 4.54 4.94 5.11 5.18 4.90 4.22 4.30 4.50 4.78 4.86 3.68 5.54 5.32 4.72 4.91 4.97 4.47 4.50 4.19 3.72 5.13
4.12 4.70 4.89 4.84 4.17 4.47 5.08 4.72 4.15 4.30 4.54 4.23 4.66 4.40 4.03 4.51 4.59 4.66 4.67 4.71 4.48 4.33 4.43 3.81 5.44
4.31 4.44 4.76 4.70 4.09 4.36 5.04 4.69 3.98 4.33 4.09 4.37 4.46 4.21 3.92 4.79 4.82 4.98 5.13 5.18 4.79 4.19 4.49 3.92 5.01
4.03 5.08 4.42 4.17 3.59 3.84 4.40 4.12 4.28 3.61 5.16 4.33 4.34 4.04 4.03 5.39 4.89 5.87 5.55 5.48 4.55 4.34 4.46 4.06 4.57
4.10 4.73 4.21 3.89 3.29 3.59 4.19 4.34 3.84 4.00 4.56 4.31 4.57 4.14 4.71 5.77 5.32 5.48 5.89 5.21 4.57 4.50 4.37 3.88 4.81
4.16 4.57 4.11 4.02 4.11 3.76 4.40 4.26 3.94 3.70 3.79 3.98 4.60 4.46 4.85 5.51 5.42 5.64 6.29 5.87 5.11 4.22 4.50 3.72 4.70
4.09 4.76 4.19 4.32 3.98 3.80 4.29 4.33 4.10 4.02 4.24 3.82 4.87 4.39 4.86 4.97 5.76 5.67 5.58 5.13 4.54 4.48 4.28 3.50 4.79
4.18 4.11 4.06 3.74 3.91 3.29 3.75 4.40 3.62 4.00 3.63 4.33 5.29 4.33 5.08 5.11 5.50 5.69 5.46 4.74 4.24 4.50 4.43 3.94 4.79
3.92 4.46 4.02 4.04 3.82 3.61 3.69 4.41 3.36 3.99 3.59 4.49 4.54 4.34 4.79 5.46 5.37 4.76 4.87 4.63 4.22 4.52 3.94 3.86 4.81
4.04 5.03 3.77 3.28 3.35 3.45 3.54 4.12 3.37 3.43 3.80 3.87 4.16 4.06 3.86 4.21 4.08 4.45 4.46 4.46 4.65 4.46 3.91 4.04 4.64
4.74 3.47 4.41 4.18 3.60 3.49 4.06 4.31 3.99 4.01 4.20 4.35 4.14 3.86 3.84 4.14 4.46 4.43 4.44 4.47 4.22 4.22 4.24 3.89 4.41

>> more fusa_counter_10m_last_return.asc
...

>> more fusa_density_10m_last_return.asc
...

Regards,

Martin @rapidlasso

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