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license: cc-by-nc-nd-4.0
tags:
  - Autonomous Driving
  - Computer Vision

Open MARS Dataset

image/jpeg


Welcome to the tutorial of Open MARS Dataset!

Our paper has been accepted on CVPR 2024 🎉🎉🎉

Checkout our project website for demo videos. Codes to reproduce the videos are available in /visualize folder of our github repo.


Intro

The MARS dataset is collected with a fleet of autonomous vehicles from MayMobility.

Our dataset uses the same structure as the NuScenes Dataset:

  • Multitraversal: each location is saved as one NuScenes object, and each traversal is one scene.
  • Multiagent: the whole set is a NuScenes object, and each multiagent encounter is one scene.

Download

Both Multiagent and Multitraversal subsets are now available for download on huggingface.


Overview

This tutorial explains how the NuScenes structure works in our dataset, including how you may access a scene and query its samples of sensor data.


Initialization

First, install nuscenes-devkit following NuScenes's repo tutorial, Devkit setup section. The easiest way is install via pip:

pip install nuscenes-devkit

Import NuScenes devkit:

from nuscenes.nuscenes import NuScenes

Load Multitraversal

loading data of location 10:

# The "version" variable is the name of the folder holding all .json metadata tables.
location = 10
nusc = NuScenes(version='v1.0', dataroot=f'/MARS_multitraversal/{location}', verbose=True)

Load Multiagent

loading data for the full set:

nusc = NuScenes(version='v1.0', dataroot=f'/MARS_multiagent', verbose=True)

Scene

To see all scenes in one set (one location of the Multitraversal set, or the whole Multiagent set):

print(nusc.scene)

Output:

[{'token': '97hitl8ya1335v8zkixvsj3q69tgx801', 'nbr_samples': 611, 'first_sample_token': 'udrq868482482o88p9r2n8b86li7cfxx', 'last_sample_token': '7s5ogk8m9id7apixkqoh3rep0s9113xu', 'name': '2023_10_04_scene_3_maisy', 'intersection': 10, 'err_max': 20068.00981996727},
{'token': 'o858jv3a464383gk9mm8at71ai994d3n', 'nbr_samples': 542, 'first_sample_token': '933ho5988jo3hu848b54749x10gd7u14', 'last_sample_token': 'os54se39x1px2ve12x3r1b87e0d7l1gn', 'name': '2023_10_04_scene_4_maisy', 'intersection': 10, 'err_max': 23959.357933579337},
{'token': 'xv2jkx6m0o3t044bazyz9nwbe5d5i7yy', 'nbr_samples': 702, 'first_sample_token': '8rqb40c919d6n5cd553c3j01v178k28m', 'last_sample_token': 'skr79z433oyi6jljr4nx7ft8c42549nn', 'name': '2023_10_04_scene_6_mike', 'intersection': 10, 'err_max': 27593.048433048432},
{'token': '48e90c7dx401j97391g6549zmljbg0hk', 'nbr_samples': 702, 'first_sample_token': 'ui8631xb2in5la133319c5301wvx1fib', 'last_sample_token': 'xrns1rpma4p00hf39305ckol3p91x59w', 'name': '2023_10_04_scene_9_mike', 'intersection': 10, 'err_max': 24777.237891737892},
...
]

The scenes can then be retrieved by indexing:

num_of_scenes = len(nusc.scene)
my_scene = nusc.scene[0]    # scene at index 0, which is the first scene of this location
print(first_scene)

Output:

{'token': '97hitl8ya1335v8zkixvsj3q69tgx801',
'nbr_samples': 611,
'first_sample_token': 'udrq868482482o88p9r2n8b86li7cfxx',
'last_sample_token': '7s5ogk8m9id7apixkqoh3rep0s9113xu',
'name': '2023_10_04_scene_3_maisy',
'intersection': 10,
'err_max': 20068.00981996727}
  • nbr_samples: number of samples (frames) of this scene.
  • name: name of the scene, including its date and name of the vehicle it is from (in this example, the data is from Oct. 4th 2023, vehicle maisy).
  • intersection: location index.
  • err_max: maximum time difference (in millisecond) between camera images of a same frame in this scene.

Sample

Get the first sample (frame) of one scene:

first_sample_token = my_scene['first_sample_token']    # get sample token
my_sample = nusc.get('sample', first_sample_token)    # get sample metadata
print(my_sample)

Output:

{'token': 'udrq868482482o88p9r2n8b86li7cfxx',
'timestamp': 1696454482883182,
'prev': '',
'next': 'v15b2l4iaq1x0abxr45jn6bi08j72i01',
'scene_token': '97hitl8ya1335v8zkixvsj3q69tgx801',
'data': {
  'CAM_FRONT_CENTER': 'q9e0pgk3wiot983g4ha8178zrnr37m50',
  'CAM_FRONT_LEFT': 'c13nf903o913k30rrz33b0jq4f0z7y2d',
  'CAM_FRONT_RIGHT': '67ydh75sam2dtk67r8m3bk07ba0lz3ib',
  'CAM_BACK_CENTER': '1n09qfm9vw65xpohjqgji2g58459gfuq',
  'CAM_SIDE_LEFT': '14up588181925s8bqe3pe44d60316ey0',
  'CAM_SIDE_RIGHT': 'x95k7rvhmxkndcj8mc2821c1cs8d46y5',
  'LIDAR_FRONT_CENTER': '13y90okaf208cqqy1v54z87cpv88k2qy',
  'IMU_TOP': 'to711a9v6yltyvxn5653cth9w2o493z4'
},
'anns': []}
  • prev: token of the previous sample.
  • next': token of the next sample.
  • data: dict of data tokens of this sample's sensor data.
  • anns: empty as we do not have annotation data at this moment.

Sample Data

Sensor Names

Our sensor names are different from NuScenes' sensor names. It is important that you use the correct name when querying sensor data. Our sensor names are:

['CAM_FRONT_CENTER',
'CAM_FRONT_LEFT',
'CAM_FRONT_RIGHT',
'CAM_BACK_CENTER',
'CAM_SIDE_LEFT',
'CAM_SIDE_RIGHT',
'LIDAR_FRONT_CENTER',
'IMU_TOP']

Camera Data

All image data are already undistorted.

To load a piece data, we start with querying its sample_data dictionary object from the metadata:

sensor = 'CAM_FRONT_CENTER'
sample_data_token = my_sample['data'][sensor]
FC_data = nusc.get('sample_data', sample_data_token)
print(FC_data)

Output: 

{'token': 'q9e0pgk3wiot983g4ha8178zrnr37m50',
'sample_token': 'udrq868482482o88p9r2n8b86li7cfxx',
'ego_pose_token': 'q9e0pgk3wiot983g4ha8178zrnr37m50',
'calibrated_sensor_token': 'r5491t78vlex3qii8gyh3vjp0avkrj47',
'timestamp': 1696454482897062,
'fileformat': 'jpg',
'is_key_frame': True,
'height': 464,
'width': 720,
'filename': 'sweeps/CAM_FRONT_CENTER/1696454482897062.jpg',
'prev': '',
'next': '33r4265w297khyvqe033sl2r6m5iylcr',
'sensor_modality': 'camera',
'channel': 'CAM_FRONT_CENTER'}
  • ego_pose_token: token of vehicle ego pose at the time of this sample.
  • calibrated_sensor_token: token of sensor calibration information (e.g. distortion coefficient, camera intrinsics, sensor pose & location relative to vehicle, etc.).
  • is_key_frame: disregard; all images have been marked as key frame in our dataset.
  • height: image height in pixel
  • width: image width in pixel
  • filename: image directory relative to the dataset's root folder
  • prev: previous data token for this sensor
  • next: next data token for this sensor

After getting the sample_data dictionary, Use NuScenes devkit's get_sample_data() function to retrieve the data's absolute path.

Then you may now load the image in any ways you'd like. Here's an example using cv2:

import cv2

data_path, boxes, camera_intrinsic = nusc.get_sample_data(sample_data_token)
img = cv2.imread(data_path)
cv2.imshow('fc_img', img)
cv2.waitKey()

Output: 

('{$dataset_root}/MARS_multitraversal/10/sweeps/CAM_FRONT_CENTER/1696454482897062.jpg',
[],
array([[661.094568 ,   0.       , 370.6625195],
       [  0.       , 657.7004865, 209.509716 ],
       [  0.       ,   0.       ,   1.       ]]))

image/png

LiDAR Data

Impoirt data calss "LidarPointCloud" from NuScenes devkit for convenient lidar pcd loading and manipulation.

The .bcd.bin LiDAR data in our dataset has 5 dimensions: [ x || y || z || intensity || ring ].

The 5-dimensional data array is in pcd.points. Below is an example of visualizing the pcd with Open3d interactive visualizer.

import open3d as o3d
from nuscenes.utils.data_classes import LidarPointCloud

sensor = 'LIDAR_FRONT_CENTER'
sample_data_token = my_sample['data'][sensor]
lidar_data = nusc.get('sample_data', sample_data_token)

data_path, boxes, _ = nusc.get_sample_data(my_sample['data'][sensor])

pcd = LidarPointCloud.from_file(data_path)
print(pcd.points)
pts = pcd.points[:3].T

# open3d visualizer
vis1 = o3d.visualization.Visualizer()
vis1.create_window(
    window_name='pcd viewer',
    width=256 * 4,
    height=256 * 4,
    left=480,
    top=270)
vis1.get_render_option().background_color = [0, 0, 0]
vis1.get_render_option().point_size = 1
vis1.get_render_option().show_coordinate_frame = True

o3d_pcd = o3d.geometry.PointCloud()
o3d_pcd.points = o3d.utility.Vector3dVector(pts)

vis1.add_geometry(o3d_pcd)
while True:
    vis1.update_geometry(o3d_pcd)
    vis1.poll_events()
    vis1.update_renderer()
    time.sleep(0.005)

Output: 

5-d lidar data: 
[[ 3.7755847e+00  5.0539265e+00  5.4277039e+00 ...  3.1050100e+00
   3.4012783e+00  3.7089713e+00]
 [-6.3800979e+00 -7.9569578e+00 -7.9752398e+00 ... -7.9960880e+00
  -7.9981585e+00 -8.0107889e+00]
 [-1.5409404e+00 -3.2752687e-01  5.7313687e-01 ...  5.5921113e-01
  -7.5427920e-01  6.6252775e-02]
 [ 9.0000000e+00  1.6000000e+01  1.4000000e+01 ...  1.1000000e+01
   1.8000000e+01  1.6000000e+01]
 [ 4.0000000e+00  5.3000000e+01  1.0200000e+02 ...  1.0500000e+02
   2.6000000e+01  7.5000000e+01]]

image/png

IMU Data

IMU data in our dataset is saved as json files.

sensor = 'IMU_TOP'
sample_data_token = my_sample['data'][sensor]
lidar_data = nusc.get('sample_data', sample_data_token)

data_path, boxes, _ = nusc.get_sample_data(my_sample['data'][sensor])

imu_data = json.load(open(data_path))
print(imu_data)

Output:

{'utime': 1696454482879084,
'lat': 42.28098291158676,
'lon': -83.74725341796875,
'elev': 259.40500593185425,
'vel': [0.19750464521348476, -4.99952995654127e-27, -0.00017731071625348704],
'avel': [-0.0007668623868539726, -0.0006575787383553688, 0.0007131154834496556],
'acc': [-0.28270150907337666, -0.03748669268679805, 9.785771369934082]}
  • lat: GPS latitude.
  • lon: GPS longitude.
  • elev: GPS elevation.
  • vel: vehicle instant velocity [x, y, z] in m/s.
  • avel: vehicle instant angular velocity [x, y, z] in rad/s.
  • acc: vehicle instant acceleration [x, y, z] in m/s^2.

Vehicle and Sensor Pose

Poses are represented as one rotation matrix and one translation matrix.

  • rotation: quaternion [w, x, y, z]
  • translation: [x, y, z] in meters

Sensor-to-vehicle poses may differ for different vehicles. But for each vehicle, its sensor poses should remain unchanged across all scenes & samples.

Vehicle ego pose can be quaried from sensor data. It should be the same for all sensors in the same sample.

# get the vehicle ego pose at the time of this FC_data
vehicle_pose_fc = nusc.get('ego_pose', FC_data['ego_pose_token'])
print("vehicle pose: \n", vehicle_pose_fc, "\n")

# get the vehicle ego pose at the time of this lidar_data, should be the same as that queried from FC_data as they are from the same sample.
vehicle_pose = nusc.get('ego_pose', lidar_data['ego_pose_token'])
print("vehicle pose: \n", vehicle_pose, "\n")

# get camera pose relative to vehicle at the time of this sample
fc_pose = nusc.get('calibrated_sensor', FC_data['calibrated_sensor_token'])
print("CAM_FRONT_CENTER pose: \n", fc_pose, "\n")

# get lidar pose relative to vehicle at the time of this sample
lidar_pose = nusc.get('calibrated_sensor', lidar_data['calibrated_sensor_token'])
print("CAM_FRONT_CENTER pose: \n", lidar_pose)

Output: 

vehicle pose: 
 {'token': 'q9e0pgk3wiot983g4ha8178zrnr37m50',
'timestamp': 1696454482883182,
'rotation': [-0.7174290249840286, 0.0, -0.0, -0.6966316057361065],
'translation': [-146.83352790433003, -21.327001411798392, 0.0]} 

vehicle pose: 
 {'token': '13y90okaf208cqqy1v54z87cpv88k2qy',
'timestamp': 1696454482883182,
'rotation': [-0.7174290249840286, 0.0, -0.0, -0.6966316057361065],
'translation': [-146.83352790433003, -21.327001411798392, 0.0]} 

CAM_FRONT_CENTER pose: 
 {'token': 'r5491t78vlex3qii8gyh3vjp0avkrj47',
'sensor_token': '1gk062vf442xsn86xo152qw92596k8b9',
'translation': [2.24715, 0.0, 1.4725],
'rotation': [0.49834929780875276, -0.4844970241435727, 0.5050790448056688, -0.5116695901338464],
'camera_intrinsic': [[661.094568, 0.0, 370.6625195], [0.0, 657.7004865, 209.509716], [0.0, 0.0, 1.0]],
'distortion_coefficient': [0.122235, -1.055498, 2.795589, -2.639154]} 

CAM_FRONT_CENTER pose: 
 {'token': '6f367iy1b5c97e8gu614n63jg1f5os19',
'sensor_token': 'myfmnd47g91ijn0a7481eymfk253iwy9',
'translation': [2.12778, 0.0, 1.57],
'rotation': [0.9997984797097376, 0.009068089160690487, 0.006271772522201215, -0.016776012592418482]}

LiDAR-Image projection

  • Use NuScenes devkit's render_pointcloud_in_image() method.
  • The first variable is a sample token.
  • Use camera_channel to specify the camera name you'd like to project the poiint cloud onto.
nusc.render_pointcloud_in_image(my_sample['token'],
                                pointsensor_channel='LIDAR_FRONT_CENTER',
                                camera_channel='CAM_FRONT_CENTER',
                                render_intensity=False,
                                show_lidarseg=False)

Output:

image/png