CavernSeer vs RTAB

Designed for cave and shelter surveying, CavernSeer leverages the LiDAR scanner of the 2020 iPad Pro and the iPhone 12 Pro, and RealityKit's scene reconstruction, to generate relatively-accurate 3D meshes of real-world spaces and render them in various convenient ways. ### App Usage ### All iOS/iPadOS 14 devices can run the app and view existing scans shared by others, but devices with a LiDAR scanner (currently iPhone 12 Pros and newer iPad Pros) can capture new scans. ### Viewing ### Scans created by the user or imported from elsewhere will appear in the "Scan List" tab, which lists out the names and the starting photo of the scan. Selecting a scan displays the start and end photos (if available), *export* options for the scan file as well as a plaintext .OBJ render, as well as the following: * Advanced - underlying information about the scan. * 3D Render - a 3D perspective rendering view navigable based on the setting "3D render interaction mode". * Plan Projected Render - a "top-down" orthographic projection complete with scale bar. Defaults to north-up. The height control allows for raising or lowering the camera to show or hide obstructions. * Elevation Projected Render - a "side-view" orthographic projection with scale bar, compass, and various controls. The angle controls change the direction the camera is facing relative to magnetic-north. The depth control is similar to the plan-projected height control, allowing for pushing the camera through obstructions. * Cross Section Render - an elevation projection (see above) with an inset plan-projection indicating the position and size of the camera, and a switch for making the camera "depth-of-field" 1-meter deep to create a cross-section slice. All of the renders support high-resolution screenshots scaled to higher detail than the device itself. ### Scanning ### Devices with a LiDAR scanner can capture new scans in the "Scanner" tab. Pressing the center button starts a scan, after which you can enable Apple's debugging overlays, either showing _Debug_ information or a _Mesh_ preview which displays the currently captured mesh on screen, as well as enabling the device's flashlight. Clicking the center button again will complete and save the scan, which will appear in the scan list. ### Settings ### * Three settings for mesh color change the way that the meshes in the various viewers are displayed. * Switch for changing between meters and decimal-feet in any distance contexts. * Setting for changing the interaction mode in the 3d Render view. The recommended option is "Orbit angle mapping". * Debugging options where appropriate.

RTAB-Map (Real-Time Appearance-Based Mapping) is an Open Source LiDAR / RGB-D / Stereo Graph-Based SLAM (Simultaneous Localization and Mapping) approach based on an online incremental appearance-based loop closure detector. The loop closure detector uses a bag-of-words approach to determinate how likely a new image comes from a previous location or a new location. When a loop closure hypothesis is accepted, a new constraint is added to the map's graph, then a graph optimizer minimizes the errors in the map in real-time. An optional memory management approach can be used to limit the number of locations used for loop closure detection and graph optimization, so that real-time constraints on large-scale environnements are always respected. ARKit's visual inertial odometry (VIO) is used as the SLAM front-end for RTAB-Map (the SLAM back-end). * Note that unlike other scanning apps that optimize the map only after mapping, with RTAB-Map you get loop closure detection and map optimization online so you can have a live feedback to know when you have enough constraints in the map for good global optimization before stopping the scan. *** 3D reconstruction available only with LiDAR sensor. Features: * Online 3D scanning/mapping of the environment. * Online loop closure detection and map correction. * Save in DB format (RTAB-Map desktop and rtabmap_ros format). * Export in PLY, LAS or OBJ. * Multi-session mapping (save and continue later). * Use Apriltags to help finding loop closures in textureless environments. * Mixed AR/VR First-Person in visualization mode. * Raw ARKit data recording (up to 60 Hz!), useful to record long sessions without comprising battery life.