Requirements and Information

General

Mavis is designed to build and process Orthomosaics and Digital Surface Models from True Color JPEG or TIF images. Images should taken with cameras facing downward, i.e. nadir or vertical. Nadir is defined < 3° tilt. However, images can be processed if the angle is < 15° tilt.

Mavis either works with geotagged images or provides georeferencing options based on Ardupilot onboard dataflash log files. Hence, it works with all Ardupilot mission planning tools such as Mission Planner, APM Planner and Tower. For georeferencing using Ardupilto log files, 3DR Solo, AC3.3 (with EKF enabled) or AC 3.4 dataflash .log files are required. Precise georeferencing is possible using CHDK enabled Canon cameras running our KAPTURE script to account for shooting delays. For direct GPS based stitching, stabilized Nadir camera gimbals are required.

We recommend using the survey tool provided in Tower (https://github.com/DroidPlanner/Tower) for mission planning.

Minimum system requirements

  • Operating system: 64 bit Windows 7, 8, 10
  • CPU: 4 cores
  • Hard disk: Fast (7200 U/min) internal HDD
  • RAM for small to medium sized datasets: 16 GB
  • Operating system: 64 bit Windows 7, 8, 10
  • CPU: 4-10 cores with hyperthreading
  • Hard disk: 512GB SSD (PCIe, M.2 or SATA)
  • RAM: 32-128 GB

Mavis Camera Setup

Global shutter cameras with a CCD sensor are recommended. Many action cameras as well as some P&S cameras use cheap CMOS sensors with rolling shutter. This might result in problems with camera calibration and/or artifacts in the orthomosaic and the Digital Surface Model. Hence, they are not recommended.

Prerequisites

One aim in developing Mavis was to provide easy and seamless georeferencing. To avoid any trouble, be sure to start your mission with an empty DCIM folder on the SD card of the camera. We suggest to use the survey tool provided in Tower for mission planning.

For precise geotagging Mavis requires a camera log file (*.cam), a UAV *.log file as well as image sets starting with image ID 1 (e.g. IMG_0001.JPG). In such a case each image can directly be linked to the corresponding camera trigger message in the UAV log file. To avoid any trouble, be sure to start your mission with an empty DCIM folder on the SD card of the camera.

To generate the *.cam log file we use KAPTURE our special version of the KAP UAV exposure script which measures the shooting delay.

Image Overlap

Camera calibration and bundle adjustment require a high degree of image overlap. In general, it should be >= 70%. We recommend an overlab of 80% and a sidelab of 75%. Low over- and sidelaps below 65% and 55% can cause problems during bundle adjustment.

Images overlapping with only 1-3 other images can cause problems during bundle adjustment as well. Such images can occur in turns, when flying under windy conditions with a hard mounted camera, and if the image overlap and side lap are insufficient. These images will be removed automatically. However, depending on the georeferencing approach they should be removed manually.

The GUI

Mavis is designed to provide a straightforward user interface.

The general GUI workflow in Mavis is top-down – left-right and organized in tabs.
Double-clicking an image in the Gallery opens it in the View.
A double-right-click opens the containing folder.
All maps and results are stored in /Mavis/Results/../.

Some pre- and postprocessing options such as shadow removal, Agrowing QX1 image processing and color calibration are organiszed in the Red Tabs section.

Files and Folders

It is strongly recommended not to open any folder or file in the workspace while any process is running. Please note that many folders and files will be generated in the workspace. Do not delete or move them until the entire processing is finished.

It is mandatory to make backups of your imagery data as well as the associated *.log and *.cam files before processing the images in Mavis.

Mavis generates and deletes many files during processing. When a virus scanners is scanning all new files this might cause conflicts and in some cases Mavis might crash. Hence, such "deep scan" options should temporarily be switched off if permitted.

Open source software

3D Mapping in Mavis is based on MicMac (http://logiciels.ign.fr/?Micmac).

Compared to the original MicMac workflow, Mavis uses a different approach for image matching/tie-point generation as well as for creating orthomosacis. We donate to the MicMac development with every copy of Mavis sold.

Apart from MicMac, Mavis uses other Open-Source-Software described in the linked document.

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