I try to refine orthorectification of a World-View
2 image with a set of GCP (17 in total). First i read .geom
file in initial image with otbcli_ReadImageInfo and try to
refine with otbcli_RefineSensorModel using my GCP. However,
resulting orthoimage using refine .geom are more shifted
(relative to those GCP) than original images.
Investigating this problem i found that height (z) estimate
from otbcli_RefineSensorModel for each GCP are not the same
that SRTM data. I use DownloadSRTMTiles application to
download srtm data and the geoid link found on the OTB
website. Here the result :
2016 Oct 17 16:29:25 : Application.logger (INFO) Adding tie
point x=4222, y=32918, z=215.755, lon=-5.22294, lat=7.16053
2016 Oct 17 16:29:25 : Application.logger (INFO) Adding tie
point x=7818, y=29136, z=215.046, lon=-5.20676, lat=7.17769
2016 Oct 17 16:29:25 : Application.logger (INFO) Adding tie
point x=3015, y=30395, z=224.989, lon=-5.22845, lat=7.17191
2016 Oct 17 16:29:25 : Application.logger (INFO) Adding tie
point x=2146, y=34611, z=227.753, lon=-5.2323, lat=7.15284
2016 Oct 17 16:29:25 : Application.logger (INFO) Adding tie
point x=8825, y=28531, z=207.521, lon=-5.20222, lat=7.18045
2016 Oct 17 16:29:25 : Application.logger (INFO) Adding tie
point x=12964, y=24821, z=252.431, lon=-5.18351, lat=7.19734
2016 Oct 17 16:29:25 : Application.logger (INFO) Adding tie
point x=20593, y=20334, z=263.199, lon=-5.14906, lat=7.2178
2016 Oct 17 16:29:25 : Application.logger (INFO) Adding tie
point x=19766, y=15039, z=259.089, lon=-5.1529, lat=7.24173
2016 Oct 17 16:29:25 : Application.logger (INFO) Adding tie
point x=7572, y=24160, z=221.765, lon=-5.20796, lat=7.20017
2016 Oct 17 16:29:25 : Application.logger (INFO) Adding tie
point x=14997, y=19624, z=238.779, lon=-5.17444, lat=7.22084
2016 Oct 17 16:29:25 : Application.logger (INFO) Adding tie
point x=19236, y=23380, z=237.795, lon=-5.15517, lat=7.20398
2016 Oct 17 16:29:25 : Application.logger (INFO) Adding tie
point x=20686, y=7548, z=259.145, lon=-5.1489, lat=7.27559
2016 Oct 17 16:29:25 : Application.logger (INFO) Adding tie
point x=16714, y=15626, z=244.571, lon=-5.16673, lat=7.23899
2016 Oct 17 16:29:25 : Application.logger (INFO) Adding tie
point x=16824, y=22630, z=253.821, lon=-5.16608, lat=7.20731
However, comparing my GCP with the SRTM data at the same
location give me those results.
My question remains to know if difference between elevation
from my GCP and those estimate by OTB are the source of the
shift of the orthorectification.