| 7 | | AGC details |
| 8 | | |
| 9 | | QC procedure (probably all in Mark's notes?) |
| 10 | | |
| 11 | | Orthophotos? (don't think we need this, plus we don't really have enough detail. Might just do a 2 paragraph thing) |
| | 7 | |
| | 8 | == QC procedures == |
| | 9 | |
| | 10 | ''Mark seems to have covered these better, key concepts only here'' |
| | 11 | |
| | 12 | Essentially all using TerraScan. The main things are: |
| | 13 | * profiles |
| | 14 | * profiles along averaged areas |
| | 15 | * profiles along a track (e.g. following a ditch / feature in the surface) |
| | 16 | * narrow profiles across features where swaths overlap |
| | 17 | * comparisons against GCPs |
| | 18 | * requires the point cloud to be converted to a surface ( |
| | 19 | |
| | 20 | |
| | 21 | == Automatic Gain Control == |
| | 22 | |
| | 23 | The intensity of a return is measured (R1-R3) as an 8 bit value (0=dark (water), 255=bright) relating to the reflectivity of the illuminated surface. The value is amplified by an automatic gain controller to keep it within 8 bit range. The value of the AGC is also measured as an 8 bit value and is recorded per pulse as the "gain control voltage" in the raw files. Typical values are 110-180. |
| | 24 | |
| | 25 | The AGC is controlled automatically in our LIDAR, but operates on a threshold basis. If there are N (64?) low intensity points in a row, the AGC will step up one level. If there are M (32?) overbright points in a row, the AGC will step down. This may lead to visible steps in the image intensity, but isn't supposed to be a big problem. Look out for streaky areas though ("contact support if you see this" - though not sure why). |
| | 26 | |
| | 27 | == RCD camera == |
| | 28 | |
| | 29 | === Orthophotos === |
| | 30 | |
| | 31 | This apparently takes another week long training course. We do have the basic software to do it but limited knowledge. Basic process is to determine the camera parameters, correct and overlay the images, keeping ideally only the most central parts. You then have to manually check through, especially along seams, and manually move the seam line in some instances (e.g. when perspective effects result in odd errors due to the seam hitting a tall building). |