Basalt Hills 2012 Data Set

Table of Contents

1 Introduction

The Intelligent Robotics Group (IRG) conducted an engieering field test with the K-Rex rover during the first week of October 2012. The field test took place at the Basalt Hills quarry, California. A large amount of data useful for research in mapping, localization, and navigation has been collected during this experiment.

1.1 K-Rex Rover

K-Rex is a four wheel drive, four wheel steer vehicle with a wheelbase of ~1.8m and track of ~1.4m, with ATV wheels 26in in diameter. Its overall size is approximately 2.0m x 1.6m and it weighs about 300kg with all its instrumentation. Its mast top is at 1.7 from the ground.

For this field experiment, the rover was equiped with a pair of stereo cameras, a 32 beam laser scanner, two different IMUs, a differential GPS and a compass. The specification of the instruments are listed in Sensor References. Photos front view and back view show K-Rex as it was outfitted for the field test. The short video illustrates the K-Rex terrain capabilities.


View of K-Rex from the front


View of K-Rex from the back

1.2 Field Site

The Basalt Hills site is an inactive quarry located next to the San Luis Reservoir, California. It is conviniently located at a 1h40min drive from the Ames Research Center. The Basalt Hills View shows an overview of the quarry.

The bottom of the quarry extends on more than 250m and spreads on multiple layers. Very little vegetation grows in the quarry and the site contains several interesting terrain features (flat, obstacles, cliffs, slopes, corridors, etc.). The rover terrain capability allows to reach different layers of the quarry and descent ~15deg slopes. Typically, the last experiment contains multiple loops on 3 different layers.


Basalt Hills Site Location


Basalt Hills Site Overview

The MapMakers of IRG produced a high resolution (0.5m/pixel) Digital Elevation Map (DEM) of the site from satellite imagery:

These DEM products are in GeoTiff format (use gdalinfo to see the datum) and elevation are coded with Float32.

To easily view the areas covered by these DEM, hillshade versions of them are also available:

1.3 Experiment

The primary goal of the field experiment was to collect a large data set of stereo images and laser scanner, together with accurate Inertial Measurement System (INS) information to support mapping and navigation work.

For this field test the rover was not driving autonomously, but was controlled using a joystick by a driver with direct view of the rover. This allowed to maximize both the amount of data collected and its quality (by following interesting paths), without being affected by any effect of the autonomous navigation normally used.

The Basalt Hill Walk photo shows the typical operation mode with one driver and one safety person behind the rover on a path overlooking the bottom of the quary. The video shows graphically the data collected using the 3D viewwer VERVE.

The result of the experiment is data collected mostly from five rover traverses ranging from 1km to 3km, totalling 11.4km. The Basalt Hills 2012 Tracks screen shot gives an overview of the tracks followed, while the Basal Hills 2012 KML file allows to load the tracks in Google Earth for closer examination. Each KML track is referenced with an icon that contains basic information about the track.


Overview of K-Rex main tracks for the field test

Experiments are referenced by their date plus a number with the following format: YYYY-MM-DD_N.

1.3.1 Log 2012-10-05_1

Short loop, staying at the bottom of the quarry (single level), with 2 small loops around mounts.

1.3.2 Log 2012-10-06_1

Simple short traverse, without loop, following a quarry cliff and going through a small "valley" at the end. The path choosen exposes a lot of high 3D features.

1.3.3 Log 2012-10-06_3 and log 2012-10-06_4

Single long loop with local loops and running on 3 levels of the quarry. This is the only traverse that contains data of the Xsens IMU and HMR3000 compass in addition to the Honeywell IMU. Unfortunately the data set is split into 2 files. The 2 data logs 2012-10-06_3 and 2012-10-06_4 need to be combined to form a full large loop. However each log can also be considered in isolation. For example on 2012-10-06_4 the rover goes down a slope that can simulate a crater descent.

1.3.4 Log 2012-10-04_5 and log 2012-10-04_5

Medium size loops running on 2 and 3 levels. This data sets do not include the Xsens IMU and HMR3000 compass and the system may be less tuned than for the 2012-10-06_[3,4] runs. However because the data set are smaller and without interruption, they can still be useful.

1.3.5 Log 2012-10-05_2

Traverse of very rough terrain and climbing steep slopes. This run was performed to test the mobility of the rover and is probably not suitable for mapping or navigation. There may be operators appearing in the field of view of the sensors.

2 Data Set Organization

K-Rex robot controller is build with IRG RoverSW that uses the OMG Data Distribution Service (DDS) standard and RAPID for all telemetry within the rover and to the external world. RAPID is an Open-Source set of NASA standardized messages and utilities for the robotic domain, which uses the DDS transport mechanism. All RAPID messages are captured during the experiment using DDS utilities.

The data is organized as followed under the current directory:

  • rtiDdsLogs: raw log file from the experiment (17GB)
  • rapidLogs: converted raw log to the Rapid format for easy replay (~15GB)
  • pgmCameraImages: stereo images (38GB)
  • textRoverPositions: CSV and KML rover positions (440MB)
  • configuration: configuration files

2.1 Experiment data

The data captured during the experiment is stored under the rtiDdsLogs directory, with one sub-directory per day (which can contain multiple logs). These log files contains all messages as a binary SQL database dump and can be "replayed" using the RTI rtireplay excecutable. Each sub-directory also contains a types directory containing the XML DDS (RAPID API) data type information.

rtireplay is a powerful tool that will generate all the messages in the exact same way that during the experiment. However it requires a RTI license. IRG released an Open-Source version of a similar tool to facilitate the use of the log files transcoded using Rapid tools (see next section).

For simple usage, position information of the robot has been extracted and is contained in easily parsable CSV files. It should be noted that the raw data files contain all the robot telemetry and a low resolution JPEG version of the images. The raw stereo images are available as a separate set (under pgmCameraImages).

The following data is available in the raw files:

2.1.1 Sensors

SensorDDS Topic NameDescription
wheel encodersrapid_joint_samplewheel positions
differential GPSrapid_gps_sampleGPS information from the OEM-3
compassrapid_float32_sample-hmrHMR 3000 compass
left camerarapid_imagesensor_sample-hazcam_front_leftsubsampled jpeg left stereo image
right camerarapid_imagesensor_sample-hazcam_front_rightsubsampled jped right stereo image
INSrapid_position_sample-insNovatel INS (Honeywell IMU + OEM-3 GPS)
laser scannerrapid_rangescan_sample32 beam Veolodyne LIDAR

2.1.2 Derived data

ProducerDDS Topic NameDescription
dead reckoningrapid_float32_sample-deadReckoningdead reckoning position
RASM mapperrapid_geometrymesh_sample3D mesh from RASM mapper
ARC C2 Mapperrapid_navmap_sample2.5D navigation map
rapid_navmap_sample-cspace_tiledmapping specific pose
rapid_navmap_sample-localmap_tiledmapping specific pose
stereorapid_pointcloud_sampleOutput of stereo
position estimatorrapid_position_samplePose estimation from INS + dead reckoning
position estimatorrapid_position_sample-relativePose estimation from IMU + dead reckoning

2.2 Rapid Logs

IRG wrote a log file replay capability built in its own Open-Source 3D visualization tool VERVE. This VERVE plugin can open and replay transcoded raw RTI log files into the Rapid format. Replaying files with the VERVE-Rapid tool is completely compatible (from a subscriber point of view) with the rtireplay system described above.

  • The transcoded log files for VERVE-Rapid replay are in the rapidLogs directory, each experiment package as a zip file
  • Instructions how to replay these log files with VERVE-Rapid are accessible on the Visualize KRex RAPID log data with VERVE page.

2.3 Stereo images sets

Images captured during the experiment are stored at full resolution in PGM format under pgmCameraImages. There is a sub-directory for each file log. Image filenames have the following pattern: hazam_front[0,1]-DECIMAL.NUMBER.pgm

  • 0 = left image
  • 1 = right image
  • DECIMAL.NUMBER = time stamp

2.4 Extracted position information

Key position information of K-Rex for each experiment has been extracted under textRoverPositions. These files expose basic information to use the data set without setting up a DDS-RAPID environement for log replay.

2.4.1 Files organization

Directory with extracted rover positions
Information about the corresponding RAPID log file ./rtiDdsLog/2012-1-0#1/RapidLogDatabase-KRex_#2_0
KML file with the "ground truth" position of the rover
KML file with the INS position and the "relative" position (from the pose estimator without GPS), including a 32m positive Z offset for correct visualization in Google Earth (discrepency between terrain and GPS)
sub-directory with individual files for each type of position for a particular RAPID log file
CSV file containg the messages TOPIC_NAME-[TOPIC_SUFFIX] from the RAPID log.
aggregated CSV file with all the topics above in a single file, time ordered.

2.4.2 Field data details

Depending on the position data, it is expressed in one of the following frames:

Position expressed in meters in UTM coordinate system. The Basalt Hills site is in the UTM Zone 10 S.
Site Frame
Reference frame aligned with the UTM grid, with 0,0 set close the site. Site frame for this data set is:
UTMZone: 10 S / Northing: 4098907.0 / Easting: 669238.0
Lat/Lon (N/W)37.0211162212 / -121.0975087332 (Altitude=374m)
Local Frame
Reference frame aligned with the UTM grid, with 0,0 set when the robot controller starts. Local frame thus changes between experiments and can even be reset is the controller is re-started during an experiment.

The table below summarizes the data fields available in the CSV files:

FileRef. FrameFields
rapid_float32_sample-deadReckoning.csvLocaltime, X position, Y position, Heading (radians)
rapid_float32_sample-hmr.csvLocaltime, roll, pitch, yaw (radians)
rapid_gps_sample.csvUTMtime, x, y, z
rapid_joint_sample.csvWheelwheel odometry in meters (see file header)
rapid_position_sample.csvSitetime, x, y, z, r, p, y
rapid_position_sample-ins.csvUTMtime, x, y, z, r, p, y
rapid_position_sample-relative.csvLocaltime, x, y, z, r, p, y
rapid_position_sample-xsens.csvUTMtime, x, y, z, r, p, y

2.5 Configuration

The robot configuration in term of locomotion geometry, sensor locations and camera calibration is captured in the following files:

3 Sensor References

The names and references to the specicications of the sensors used during the field test are listed below.

3.3 Honeywell IMU (combines with OEM-3 to form turnkey INS): HG1700 from Novatel

3.6 Compass/Inclinometer: HMR3000 (Honeywell)

Author: Lorenzo Flueckiger

Date: 2013-12-02 13:13:37 PST

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