| | 72 | == Recommendations == |
| | 73 | |
| | 74 | Perform calibrations frequently at the start of the period to get a feel for how they hold. Reduce down to fit circumstances over time. |
| | 75 | |
| | 76 | == Required items for processing == |
| | 77 | |
| | 78 | Items required from every flight: |
| | 79 | * GPS/IMU data |
| | 80 | * Raw laser data |
| | 81 | * Logfiles from LIDAR |
| | 82 | * Flight logfiles are useful too, if the LIDAR flight planning software is used |
| | 83 | * RCD & webcam images |
| | 84 | |
| | 85 | Items required in general: |
| | 86 | * calibration (see elsewhere) |
| | 87 | * lever arm measurements |
| | 88 | |
| | 89 | = Processing = |
| | 90 | == Extraction == |
| | 91 | |
| | 92 | Use IPAS Pro to extract GPS, IMU and laser data from the raw files. |
| | 93 | * probably worth having the real time navigation info (doesn't add a lot of processing time) |
| | 94 | * during extraction, view the listing and verify the lever arms are correct (IMU one should never change). |
| | 95 | * look out for data gaps (listed in log) |
| | 96 | |
| | 97 | Most Leica systems are mounted "laser backwards" (cables will be at the rear if this is so) - ensure that z=180 in the IPAS Pro aircraft tab. |
| | 98 | |
| | 99 | == Navigation processing == |
| | 100 | |
| | 101 | See other pages on navigation processing as they cover this already. |
| | 102 | |
| | 103 | |
| | 104 | == Initial QC == |
| | 105 | |
| | 106 | See if the lines are too short or if the point cloud has poor return %s. If so, check the following (look at webcam images for hints): |
| | 107 | * clouds |
| | 108 | * height problem ("range gate" issue) |
| | 109 | * eyesafe shutoff (too close to ground) |
| | 110 | * too high may give dropouts |
| | 111 | * find altitude over ground (measured GPS alt - geoid-spheroid height) and see if it's within the min & max ranges |
| | 112 | |
| | 113 | -------------------------- |
| | 114 | = Calibration = |
| | 115 | |
| | 116 | == Parameters needing calibration == |
| | 117 | |
| | 118 | Lever arm measurements: |
| | 119 | * IMU -> sensor head (centre of mirror?) |
| | 120 | * Measured in the factory and provided by Leica |
| | 121 | * IMU -> measurement point [front left corner of the casing] |
| | 122 | * Measured in factory and provided by Leica |
| | 123 | * measurement point -> GPS antenna centre |
| | 124 | * '''We need to measure this one with a survey''' |
| | 125 | |
| | 126 | Intensity Based Range Correction (IBRC). |
| | 127 | * A range correction based on the reflectivity of the target object ("reflections are slower on darker objects"? perhaps this is more that a lower intensity return may take longer to be detected - ie. takes longer for enough photons to come back to exceed the detection threshold). |
| | 128 | * Measured in factory and provided by Leica. |
| | 129 | |
| | 130 | Range offset correction. |
| | 131 | * Correction for the slightly different timing of the 4 range cards in the system |
| | 132 | * At a set distance, the range cards should all return the same result |
| | 133 | * '''Measured by Leica but also measured and verified in calibration procedure.''' (see below) |
| | 134 | |
| | 135 | |
| 99 | | == Required items for processing == |
| 100 | | |
| 101 | | Items required from every flight: |
| 102 | | * GPS/IMU data |
| 103 | | * Raw laser data |
| 104 | | * Logfiles from LIDAR |
| 105 | | * Flight logfiles are useful too, if the LIDAR flight planning software is used |
| 106 | | * RCD & webcam images |
| 107 | | |
| 108 | | Items required in general: |
| 109 | | * calibration (see elsewhere) |
| 110 | | * lever arm measurements |
| 111 | | |
| 112 | | == Parameters needing calibration == |
| 113 | | |
| 114 | | Lever arm measurements: |
| 115 | | * IMU -> sensor head (centre of mirror?) |
| 116 | | * Measured in the factory and provided by Leica |
| 117 | | * IMU -> measurement point [front left corner of the casing] |
| 118 | | * Measured in factory and provided by Leica |
| 119 | | * measurement point -> GPS antenna centre |
| 120 | | * '''We need to measure this one.''' |
| 121 | | |
| 122 | | Intensity Based Range Correction (IBRC). |
| 123 | | * A range correction based on the reflectivity of the target object ("reflections are slower on darker objects"? perhaps this is more that a lower intensity return may take longer to be detected - ie. takes longer for enough photons to come back to exceed the detection threshold). |
| 124 | | * Measured in factory and provided by Leica. |
| 125 | | |
| 126 | | = Processing = |
| 127 | | == Extraction == |
| 128 | | |
| 129 | | Use IPAS Pro to extract GPS, IMU and laser data from the raw files. |
| 130 | | * probably worth having the real time navigation info (doesn't add a lot of processing time) |
| 131 | | * during extraction, view the listing and verify the lever arms are correct (IMU one should never change). |
| 132 | | * look out for data gaps (listed in log) |
| 133 | | |
| 134 | | Most Leica systems are mounted "laser backwards" (cables will be at the rear if this is so) - ensure that z=180 in the IPAS Pro aircraft tab. |
| 135 | | |
| 136 | | == Navigation processing == |
| 137 | | |
| 138 | | See other pages on navigation processing as they cover this already. |
| | 162 | == Range offset calibration == |
| | 163 | * Two datasets required: |
| | 164 | * BIT (Built-In Test) mode data, where the range cards are all fed with identical fake data representing the same distance. All cards should give the same result, so differences are used to calibrate each card against the others. |
| | 165 | * A real dataset with |