Changes between Version 7 and Version 8 of Sensors/LeicaLIDAR/FWMikesNotes


Ignore:
Timestamp:
Feb 8, 2010 1:11:49 PM (10 years ago)
Author:
mggr
Comment:

--

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  • Sensors/LeicaLIDAR/FWMikesNotes

    v7 v8  
    3636flightline log file says if WFD on/off
    3737 
    38 always produces las 1.3 file (despite currently saying 1.2)
    39  - filename ends _4.las O_o
    40  - unless you choose las 1.0 from the output options, but you must also check the output with timestamp option
    41 trigger delay settings
    42  - TPR = transition pulse rate, when the lidar changes from long pulses to short ones
    43  - for our system, >100KHz = 4ns pulse, <100kHz = 9ns pulse
    44  - each must be calibrated separately..
    45   - ie. calibration must include one above and one below TPR
    46  - possibly also temperature dependent.  shonk.
    47  - should be able to do this with bit mode data?
    48   - possible hardware issue preventing this, definite software issue (fcms doesn't record fwd in bitmode)
    49   - definite killer: timing known to verify within a flightline
    5038   
     39
     40
     41things one can detect.. maybe..
     42 - pulse stretching (return pulse longer than laser pulse
     43  - slopes
     44  - low vegetation (ie. may need to adjust "ground" peak downwards a little)
     45 - indication of biomass by evaluating area under peak
     46 - better vertical resolution/distinction of objects
     47
     48angle of laser may make a difference  (flat ground at nadir is a slope at edge of fov, or cutting through vegetation)
     49
     50
     51
     52where did gain come from in waveform viewer
     53 - volts= digitized value * gain + offset
     54 - not agc gain, this is a fixed amplication on the waveform board
     55 - value is 0.017290626
     56 - offset is also hardcoded, value is 0
     57 - system digitises from 0 to 4.something volts
     58 - gives you volts as received at the waveform board, after AGC applied, etc - probably only useful for engineering team
     59 
     60
     61ops changes: various.. relevantish ones to us are
     62 - hardware is now licensed (ie. turns into a paperweight if expires)
     63 - automatic bit mode at start and end of fcms session
     64 - moving to ethernet comms rather than rs232
     65
     66
     67  * Nothing has changed for the AGC/mainboard of the ALS so the raw laser .SCN files will be the same as before.
     68  * Extra files will be created that contain the waveform data. Waveform files (.LWV) will be in the raw_wfd directory, SCN files in the raw_laser directory.
     69  * Waveform files have A or B in filename depending on which data board (A or B) acquired it. When processing both files are taken together.
     70 * The digitiser starts recording from the first returned peak for the number of required samples (256/128 @ 1ns or 256/128/64 @ 2ns)
     71  * If first return is noise (cloud/seagull) then the digitiser will start recording there and not at the target.
     72  * measured heights / distances for different sampling rates:
     73
     74    || Sample rate || equivalent height ||
     75    || 256 @ 1ns   || 38.4m ||
     76    || 128 @ 1ns   || 19.2m ||
     77    || 256 @ 2ns   || 76.8m ||
     78    || 128 @ 2ns   || 38.4m ||
     79    || 64 @ 2ns    || 19.2m ||
     80  * the data rate is approximately 160GB/hr at full rate (256samples / 1ns).
     81 * Benefits of full waveform
     82  * Better idea of the nature of the return e.g. tree canopy height is more accurate than from 1 discrete point
     83  * Extraction of points from the waveform missed by the discrete measuring
     84  * (a future benefit) pulse stretching at swath edges compared to nadir: indicating sloped terrain, improved classification
     85 * Maximum rate of acquiring digitised full waveform data is 120KHz. If a higher rate is used then the waveform data will record for every other emitted pulse. But the SCN files will still be recorded at the high rate.
     86 * Pulse length (sampling rate) should be chosen based on the maximum height of targets in the area. E.G. if all low lying targets then there is no point using 256 samples at 1 ns - better to use 128 at 1 ns.
     87 * No changes to the calibration flights except to collect FW data. Only change to the processing is to find the timing offset between FW and discrete points.
     88 * Pre-trigger - like a buffer zone to record digitised samples before the first return. Default is 5m.
     89 * Waveform and discrete data use different scalers for the intensity values and so will result in different intensities.
     90 * AGC is constant for a pulse - so the same value is used for the entire waveform
     91 * There is a slight delay between SCN files and waveform files being recorded (< 1 second). This may result in first few points not having waveform data.
     92
     93== Software ==
     94
     95 * ALSPP outputs in LAS 1.3 (type 4?) format which supports full waveform data (and also LAS 1.0)
     96  * To output in LAS v1.0 you must also select "LAS file with time stamp" in output options else no files will be output
     97 * ALSPP takes 10 times as long to process the data to produce a LAS file when using FWD
     98 * Includes a simple waveform viewer
     99  * Displays waveform and discrete points
     100  * There is a "constant" timing offset between the waveform and discrete points - thought to be due to processing time. This should be removed at calibration
     101  * In waveviewer "Ret point loc" is the discrete return time (from emit to receive) for the first return
     102  * intensity is the value for each discrete return
     103 * LASHistoViewer is useful for viewing stats of LAS file. Can also "drag and drop" Flightline_log into it to see info and stats together.
     104 * New version of Terrascan capable of displaying full waveform data and "creating extra" points from the waveform
     105
    51106processing time
    52107 - discrete only, maybe 30secs per line
     
    93148 - check out other software, fullanalyze?
    94149
    95 
    96 
    97 RCD changes
    98  - uses full CCD instead of cut down area
    99   - 7162x5389 -> 7212x5408, 7012x5208 after geometric enhancement
    100   - see presentation for depressing readout location on old setup
    101  - change to SSD
    102  - new workflow software
    103   - file renaming to flightline/project naming from fcms
    104   - distortion removal, shutter correction
    105   - DTM support, for displaying in workflow manager
    106   = big change, but we don't use this
    107   * however, we probably should as this seems to be the bit that does distortion fixups..?
    108    - not ready yet.. maybe next week
    109  - post processing sw -> 1.2
    110   - no breaker changes
    111   - minimised L/R imbalance, improved radiometric using ccd border area (hrm)
    112 
    113 things one can detect.. maybe..
    114  - pulse stretching (return pulse longer than laser pulse
    115   - slopes
    116   - low vegetation (ie. may need to adjust "ground" peak downwards a little)
    117  - indication of biomass by evaluating area under peak
    118  - better vertical resolution/distinction of objects
    119 
    120 angle of laser may make a difference  (flat ground at nadir is a slope at edge of fov, or cutting through vegetation)
    121 
    122 software changes
    123  - hardware done, most software beta or not done yet
    124  - various operation changes
    125  - fcms now creates proper structure for file outputs, but only for the laser - rcd isn't done!
    126   - may change some of our naming ("WebCamImages" or something like that)
    127  - waveform viewer s/w
    128  - alspp outputting in las 1.3 type 4 (option to output 1.0 if needed for compat)
    129  - version list in presentation
    130 
    131 where did gain come from in waveform viewer
    132  - volts= digitized value * gain + offset
    133  - not agc gain, this is a fixed amplication on the waveform board
    134  - value is 0.017290626
    135  - offset is also hardcoded, value is 0
    136  - system digitises from 0 to 4.something volts
    137  - gives you volts as received at the waveform board, after AGC applied, etc - probably only useful for engineering team
    138  
    139 bit mode
    140  - actually could process it!
    141  - interesting underflow spike
    142  - engineering think trigger delay shouldn't change with time, but may with temperature?
    143  - not sure if bit mode vs lase mode will have a different delay, not tested
    144  - fcms will record waveform bit mode data, will in version approximately 3.2.2? probably 6 months
    145  - should ensure you have full nav solution for maximum gps timing accuracy (ie. don't just switch on ipas and record, wait a few mins first)
    146  - need two recordings for bitmode, at pulse rates above and below TPR
    147  
    148 gps time difference between line time in alspp summary and waveform viewer times
    149  - Yuji checking
    150  
    151 lashisto viewer
    152  - can look at las files with it, gives various useful info
    153  - drag and drop a log file into it to get nicely parsed info
    154 
    155 
    156 
    157 terrascan
    158  - displays waveform as colour coded line along angle of ray
    159   - can set thresholds and ranges for colour coding
    160 
    161 future processing
    162  - gaussian fitting to fwd data
    163  - working with vienna uni guys
    164 
    165 ops changes: various.. relevantish ones to us are
    166  - hardware is now licensed (ie. turns into a paperweight if expires)
    167  - closing fcms shuts the system down cleanly
    168  - need to use fpes10 for planning
    169  - automatic bit mode at start and end of fcms session
    170  - moving to ethernet comms rather than rs232
    171 
    172 processing changes
    173  - require alspp 2.69 or grater
    174  - GPS leverarms refer now to PAV80 rotation center (stabilised mount for camera, we don't have one)
    175   - PAV80 would be underneath the scanner
    176   * see slides for update formula
    177   * update wiki
    178   - alspp takes account of this if .sup file has a flag saying it was run with new fcms (sup comes from modern ipas pro)
    179   - lever arm measurement is the same, but you must include the offset to the virtual pav80
    180   - note this doesn't apply to IMU - this is a fixed offset and entered into fcms
    181    * check it's right ;p
    182    - fixed offset is apparently x=-0.411, y=0.206, z=-0.192
    183    - fcms also has a user defined offset currently set that is the offset from the pav80 back to the mirror
    184     - this is x=0.142, y=0.001, z=-0.188
    185     * this possibly should be zeroed - Yuji checking if having it set will cause a double offset to be applied
    186   - check lever arm error (should be small, a few cm)
    187  - new option in alspp to process waveform
    188  - trigger delay in pico secs (= splitter circuit delay)
    189   - one for 4ns one for 9ns pulse width (!)
    190   - but no difference for A & B boards.. hrm
    191  - order of 10x slower processing
    192 
     150always produces las 1.3 file (despite currently saying 1.2)
     151 - filename ends _4.las O_o
     152 - unless you choose las 1.0 from the output options, but you must also check the output with timestamp option
     153trigger delay settings
     154 - TPR = transition pulse rate, when the lidar changes from long pulses to short ones
     155 - for our system, >100KHz = 4ns pulse, <100kHz = 9ns pulse
     156 - each must be calibrated separately..
     157  - ie. calibration must include one above and one below TPR
     158 - possibly also temperature dependent.  shonk.
     159 - should be able to do this with bit mode data?
     160  - possible hardware issue preventing this, definite software issue (fcms doesn't record fwd in bitmode)
     161  - definite killer: timing known to verify within a flightline
     162
     163
     164== Something ==
     165
     166 * When processing data collected after using FCMS v3.15 (anything after Jan 2010 ?)
     167  * ALS system refers to a virtual rotation axis (assumes a PAV80 stabilised mount even if you do not have one)
     168  * we need to update GPS lever arms in FCMS v3.15.
     169  * .SUP file will automatically offset to the mirror centre in ALSPP processing (Need IPAS version 1.35 for this)
     170  * Unsure as to whether leverarms need to be updated in IPAS or not - also how do we know IMU offsets to apply?
    193171
    194172IMU discussion
     
    199177  - IMU can pick this up and it'll show as banding alongtrack (for pitch errors) in the data
    200178
    201 
    202   * Nothing has changed for the AGC/mainboard of the ALS so the raw laser .SCN files will be the same as before.
    203   * Extra files will be created that contain the waveform data. Waveform files (.LWV) will be in the raw_wfd directory, SCN files in the raw_laser directory.
    204   * Waveform files have A or B in filename depending on which data board (A or B) acquired it. When processing both files are taken together.
    205  * The digitiser starts recording from the first returned peak for the number of required samples (256/128 @ 1ns or 256/128/64 @ 2ns)
    206   * If first return is noise (cloud/seagull) then the digitiser will start recording there and not at the target.
    207   * measured heights / distances for different sampling rates:
    208 
    209     || Sample rate || equivalent height ||
    210     || 256 @ 1ns   || 38.4m ||
    211     || 128 @ 1ns   || 19.2m ||
    212     || 256 @ 2ns   || 76.8m ||
    213     || 128 @ 2ns   || 38.4m ||
    214     || 64 @ 2ns    || 19.2m ||
    215 
    216 data rate / height stuff
    217  - 19.2 / 38.4 / 76.8m for various heights
    218  - 1h04 recording at max rate on 160GB SSD
    219 
    220  * Benefits of full waveform
    221   * Better idea of the nature of the return e.g. tree canopy height is more accurate than from 1 discrete point
    222   * Extraction of points from the waveform missed by the discrete measuring
    223   * (a future benefit) pulse stretching at swath edges compared to nadir: indicating sloped terrain, improved classification
    224  * Maximum rate of acquiring digitised full waveform data is 120KHz. If a higher rate is used then the waveform data will record for every other emitted pulse. But the SCN files will still be recorded at the high rate.
    225  * Pulse length (sampling rate) should be chosen based on the maximum height of targets in the area. E.G. if all low lying targets then there is no point using 256 samples at 1 ns - better to use 128 at 1 ns.
    226  * No changes to the calibration flights except to collect FW data. Only change to the processing is to find the timing offset between FW and discrete points.
    227  * Pre-trigger - like a buffer zone to record digitised samples before the first return. Default is 5m.
    228  * Waveform and discrete data use different scalers for the intensity values and so will result in different intensities.
    229  * AGC is constant for a pulse - so the same value is used for the entire waveform
    230  * There is a slight delay between SCN files and waveform files being recorded (< 1 second). This may result in first few points not having waveform data.
    231 
    232 == Software ==
    233 
    234  * ALSPP outputs in LAS 1.3 format which supports full waveform data (and also LAS 1.0)
    235   * To output in LAS v1.0 you must also select "LAS file with time stamp" in output options else no files will be output
    236  * ALSPP takes 10 times as long to process the data to produce a LAS file when using FWD
    237  * Includes a simple waveform viewer
    238   * Displays waveform and discrete points
    239   * There is a "constant" timing offset between the waveform and discrete points - thought to be due to processing time. This should be removed at calibration
    240   * In waveviewer "Ret point loc" is the discrete return time (from emit to receive) for the first return
    241   * intensity is the value for each discrete return
    242  * LASHistoViewer is useful for viewing stats of LAS file. Can also "drag and drop" Flightline_log into it to see info and stats together.
    243  * New version of Terrascan capable of displaying full waveform data and "creating extra" points from the waveform
    244 
    245 
    246 == Something ==
    247 
    248  * When processing data collected after using FCMS v3.15 (anything after Jan 2010 ?)
    249   * ALS system refers to a virtual rotation axis (assumes a PAV80 stabilised mount even if you do not have one)
    250   * we need to update GPS lever arms in FCMS v3.15.
    251   * .SUP file will automatically offset to the mirror centre in ALSPP processing (Need IPAS version 1.35 for this)
    252   * Unsure as to whether leverarms need to be updated in IPAS or not - also how do we know IMU offsets to apply?
    253 
     179future processing
     180 - gaussian fitting to fwd data
     181 - working with vienna uni guys
    254182
    255183== Changes to processing ==
     
    282210   * can export the waveforms as txt files for further analysis in other software
    283211
     212lashisto viewer
     213 - can look at las files with it, gives various useful info
     214 - drag and drop a log file into it to get nicely parsed info
     215
     216
     217
     218terrascan
     219 - displays waveform as colour coded line along angle of ray
     220  - can set thresholds and ranges for colour coding
     221
     222processing changes
     223 - require alspp 2.69 or grater
     224 - GPS leverarms refer now to PAV80 rotation center (stabilised mount for camera, we don't have one)
     225  - PAV80 would be underneath the scanner
     226  * see slides for update formula
     227  * update wiki
     228  - alspp takes account of this if .sup file has a flag saying it was run with new fcms (sup comes from modern ipas pro)
     229  - lever arm measurement is the same, but you must include the offset to the virtual pav80
     230  - note this doesn't apply to IMU - this is a fixed offset and entered into fcms
     231   * check it's right ;p
     232   - fixed offset is apparently x=-0.411, y=0.206, z=-0.192
     233   - fcms also has a user defined offset currently set that is the offset from the pav80 back to the mirror
     234    - this is x=0.142, y=0.001, z=-0.188
     235    * this possibly should be zeroed - Yuji checking if having it set will cause a double offset to be applied
     236  - check lever arm error (should be small, a few cm)
     237 - new option in alspp to process waveform
     238 - trigger delay in pico secs (= splitter circuit delay)
     239  - one for 4ns one for 9ns pulse width (!)
     240  - but no difference for A & B boards.. hrm
     241 - order of 10x slower processing
     242
    284243== RCD105 ==
    285244 * Enhancements
     
    292251 * RCD workflow manager software looks useful - includes ORIMA dll file for running APM (?)
    293252 * New software should handle pixel saturation better and supports 2 CCD sizes
     253
     254RCD changes
     255 - uses full CCD instead of cut down area
     256  - 7162x5389 -> 7212x5408, 7012x5208 after geometric enhancement
     257  - see presentation for depressing readout location on old setup
     258 - change to SSD
     259 - new workflow software
     260  - file renaming to flightline/project naming from fcms
     261  - distortion removal, shutter correction
     262  - DTM support, for displaying in workflow manager
     263  = big change, but we don't use this
     264  * however, we probably should as this seems to be the bit that does distortion fixups..?
     265   - not ready yet.. maybe next week
     266 - post processing sw -> 1.2
     267  - no breaker changes
     268  - minimised L/R imbalance, improved radiometric using ccd border area (hrm)