Preparing a single session map: optimization, loop-closure¶

This tutorial will go through some commands to optimize and improve a map.

The commands in this tutorial assumes that you have loaded a VI map into the maplab console. You can get a VI map from the [[Sample Datasets]] page.

Landmark retriangulation¶

The command rtl retriangulates all landmarks in the VI map and reevaluates their quality.

Note: ROVIOLI already retriangulates all landmarks before the VI map is saved.

Note: output of commands¶

Most of the text output of the commands is hidden by default. You can see more detailed output of each command by using the standard Google Logging -v=<log_level> command. You can try to call:

rtl -v=3

to increase the verbosity and then standard:

rtl

and compare the output. The -v switch can be used with each maplab console command.

Keyframing¶

The command kfh applies a heuristics-based keyframing on the VI map. This will remove certain vertices from the map and merge the neighboring edges.

The following options are available:

Flag | Description —-|—– kf_distance_threshold_m | Maximum distance in meters between two consecutive keyframes. kf_rotation_threshold_deg | Maximum rotation in degrees between two consecutive keyframes. kf_every_nth_vertex | Forces a keyframe after every n-th vertex. kf_min_shared_landmark_obs | If two vertices share less landmarks than specified by this flag, both will be kept as a kayeframe.

Loop closure¶

The command lc searches the map for loop closures. See the loop closure tutorial for more details.

Bundle adjustment¶

The main commands for bundle adjustment (BA) are:

optvi: visual-inertial BA over the entire map.
optv: visual only BA.

The BA iteratively tries to optimize the map. During this process, a status output is printed after each step:

I1102 14:05:34.031795 10394 vi-map-optimizer.cc:85] Loading data for optimization, num of baseframes: 3
I1102 14:05:34.032006 10394 vi-map-optimizer.cc:157] Fixing 1 vertex poses.
I1102 14:05:34.117878 10394 graph-ba-optimizer.cc:1735] Removing landmarks that are still located behind the camera...
I1102 14:05:34.153887 10394 graph-ba-optimizer.cc:1741] Landmark count before: 345282
I1102 14:05:37.985208 10394 graph-ba-optimizer.cc:1779] Landmarks count after: 345282
I1102 14:05:37.985256 10394 graph-ba-optimizer.cc:2019] Adding visual term residual blocks...
I1102 14:05:47.078414 10394 graph-ba-optimizer.cc:2118] Added 2820048 visual residuals.
I1102 14:05:47.078451 10394 graph-ba-optimizer.cc:1253] Adding inertial term residual blocks...
I1102 14:05:47.137904 10394 graph-ba-optimizer.cc:1349] Added 9405 inertial residuals.
I1102 14:05:53.300902 10394 compressed_row_sparse_matrix.cc:85] # of rows: 5781171 # of columns: 407034 max_num_nonzeros: 87019350. Allocating 1067356888
iter      cost      cost_change  |gradient|   |step|    tr_ratio  tr_radius  ls_iter  iter_time  total_time
   0  1.672713e+09    0.00e+00    7.84e+08   0.00e+00   0.00e+00  1.00e+05        0    3.07e+00    7.65e+00
I1102 14:05:57.486155 10394 compressed_row_sparse_matrix.cc:85] # of rows: 407034 # of columns: 407034 max_num_nonzeros: 1390428. Allocating 18313276
   1  4.152947e+06    1.67e+09    1.66e+06   6.47e+01   1.00e+00  3.00e+05        1    3.07e+01    3.84e+01
I1102 14:06:28.178833 10394 compressed_row_sparse_matrix.cc:85] # of rows: 407034 # of columns: 407034 max_num_nonzeros: 1390428. Allocating 18313276
   2  3.115350e+06    1.04e+06    1.20e+06   3.86e+01   1.32e+00  9.00e+05        1    2.54e+01    6.38e+01
I1102 14:06:53.547498 10394 compressed_row_sparse_matrix.cc:85] # of rows: 407034 # of columns: 407034 max_num_nonzeros: 1390428. Allocating 18313276
   3  2.817663e+06    2.98e+05    4.83e+05   3.35e+01   1.39e+00  2.70e+06        1    2.44e+01    8.82e+01
I1102 14:07:17.925948 10394 compressed_row_sparse_matrix.cc:85] # of rows: 407034 # of columns: 407034 max_num_nonzeros: 1390428. Allocating 18313276
   4  2.699968e+06    1.18e+05    3.13e+05   3.53e+01   1.37e+00  8.10e+06        1    2.46e+01    1.13e+02
I1102 14:07:42.562119 10394 compressed_row_sparse_matrix.cc:85] # of rows: 407034 # of columns: 407034 max_num_nonzeros: 1390428. Allocating 18313276
   5  2.650624e+06    4.93e+04    1.22e+05   3.82e+01   1.31e+00  2.43e+07        1    2.49e+01    1.38e+02
I1102 14:08:07.494915 10394 compressed_row_sparse_matrix.cc:85] # of rows: 407034 # of columns: 407034 max_num_nonzeros: 1390428. Allocating 18313276
   6  2.628611e+06    2.20e+04    3.61e+04   5.47e+01   1.22e+00  7.29e+07        1    2.48e+01    1.63e+02
I1102 14:08:32.348891 10394 compressed_row_sparse_matrix.cc:85] # of rows: 407034 # of columns: 407034 max_num_nonzeros: 1390428. Allocating 18313276
   7  2.617790e+06    1.08e+04    4.79e+04   1.38e+02   1.07e+00  2.19e+08        1    2.54e+01    1.88e+02
I1102 14:08:57.799083 10394 compressed_row_sparse_matrix.cc:85] # of rows: 407034 # of columns: 407034 max_num_nonzeros: 1390428. Allocating 18313276

By pressing Ctrl+C, the BA will terminate after the current step is finished.

Localization map¶

To use a VI map as a localization map for ROVIOLI, two paths exist from the console:

The optimized VI map can be saved and loaded as a localization map into ROVIOLI.
The optimized VI map can be saved as a localization summary map. A localization summary map only contains the information necessary to perform localization (i.e., vertex poses and landmark descriptors and positions). The following command saves a localization summary map:

generate_summary_map_and_save_to_disk --summary_map_save_path path/to/save/localization/summary/map