Gimbal logs by connecting a USB-C cable to an unpowered gimbal and a computer, navigating to freefly > movi > logs, and copying the latest file. Share with support to expedite any gimbal-related ticket issues.

The standard workflow for mapping with Astro takes photos from the camera, geotags them, and writes them to the attached USB stick. The usb stick will contain data from each flight in separate folders.

Directory structure on the USB drive is as follows

Folder name

Naming: <SequentialFlightNumber>_<DATE>_<TIME>

There may be multiple folders that start with the same <SequentialFlightNumber> if photos were taken on the ground but without a flight.

Each folder will contain the following:

Observation file: <SequentialFlightNumber>_<DATE>_<TIME>.obs

This file contains the GNSS observations from the aircraft's RTK GPS, and is used in conjunction with the base station data to precisely locate the astro in space. The file also includes RTKlib-style "marker" entries at the timestamp when each photo was taken

Photo capture information file: <SequentialFlightNumber>_<DATE>_<TIME>-sequence.json

This JSON formatted file includes the precise timestamp and gimbal angle for each photo captured.

Aircraft capture state information file: imagelog.json

This JSON formatted file includes the aircraft position, attitude, timestamp, and capture url for each photo taken.

Photo capture information file

Name: YYYY-MM-DD-[SequentialNumber matching directory].json

Photos

File type: JPG

Naming: per camera settings

Geotags: Each photo is geotagged in its EXIF header, including geographic position and altitude in WGS84 (GPS) coordinate frame. The altitude in the aircraft geotags is based on the EGM96 geoid.

Note that additional tag information may be written later when post processed by a PPK app.

thumb

This folder contains small 512x341 thumbnails of the photos taken. They are geotagged as well, and are sometimes useful to upload to a photo photogrammetry site such as ESRI sitescan to ensure that photos are geotagged as expected. They can even be used to create a quick, coarse map.

Example output

Note that Base Station observation files are also included in separate folders in case you'd like to perform PPK.

Camera Calibration Parameters

This is a set of example calibration values for the Sony A7R-IV with Sigma 24 mm lens, which can be used for photogrammetry initial conditions. The LR1 also matches this specification with the 24mm lens. Each lens is slightly different, but these values are good initial values if the software in use can't solve them directly.

The mapping workflow is largely the same between the LR1 Payload and A7R4 payload. The same lens and camera settings are recommended for both payloads, and the same tips for maximizing efficiency are shared between them. The PPK process and output specification are also the same.

Integrated payloads developed by Freefly share much of the same information for updating gimbal firmware, isolator configurations, workflow tips, and formatting storage devices. Payload specific workflows, information, and settings are covered in the above sections.

Workflows

Maintenance

Updates

Weather

Weather is a big driver of how good the resulting maps will be. Because of lens limits and the requirement for high shutter speeds to reduce motion blur, maps are best when taken with bright light. The best results are around noon when the sun is directly overhead and casting few shadows; a bright, overcast day also works well for similar reasons.

When ambient light is low due to heavy clouds or in the evenings, the camera will expose the scene but will have to increase ISO to get reasonable exposure. Beyond ISO 1000, noise and blur from the denoising filter in the camera will start to impact photo quality.

If light conditions are low, the shutter speed can be reduced. However, the drone will need to fly slower to ensure no motion blur. The camera lens is sharpest above f/5, but the aperture can be opened up to provide more light. Some lens artifacts and blurring around the edges may be present with a wider aperture/lower f-stop.

Additionally, flying over wet surfaces may cause problems for photogrammetry workflows. It tends to make asphalt very dark, which can cause stitching software to have a hard time, and reflective surfaces can't be used to stitch photos.

Download Maps for Offline Use

AMC caches recent maps. To make certain that maps for a specific location are stored on your remote controller before you go to a site with no internet, download them while the remote controller is connected to wifi.

Plan a Mission

1. Figure out the minimum safe flying altitude at your site (i.e. above obstacles and giving a good line of sight). Enter this value in AMC > Vehicle Setup > Safety > Return Altitude.

3. Open AMC Plan view, and select "Pattern" in the left sidebar (creates flight path that covers the site and automatically triggers photos). Choose a pattern type and shape and it'll appear on the map. Don't detail the shape yet- We'll come back to that.

4. In the Pattern/Survey waypoint settings, open the Camera tab, and select Preset: Sony ILX-LR1 - 24 mm SIGMA.

5. Set Altitude. Start in Pattern waypoint settings and enter the minimum safe value from step 1. Check the Ground Sample Distance (GSD) value at the bottom of Pattern Waypoint settings. If GSD is smaller than your needs, increase altitude to increase GSD. Then go to Mission Waypoint settings and enter the same altitude.

6. Turn on Terrain Display by selecting the square T button in the bottom-left corner. Check the heightmap to make sure the flight path clears the terrain by a comfortable margin.

7. Set speed. Check the Photo Interval value at the bottom of Survey settings along the right. This interval needs to be 2 seconds or more. If it's less, decrease the mission flight speed or increase forward overlap (if this is acceptable for your mission). If the photo interval is larger than 2 seconds, you can optionally increase your flight speed.

8. Adjust the Pattern area. Make sure the green area (the area to be flown and photographed) is larger than the map you need. Make the green area larger on every side by at least the width between flight passes. Note the estimated flight duration at the top of the screen. If the duration is longer than 23 minutes, it's likely to require a second flight.

9. Add a Return waypoint command if you want the aircraft to come home and land when finished. This is optional but recommended. If the mission's last command is a Pattern or Waypoint, AMC will not notify you that the mission has ended. The aircraft will hover at the last waypoint, likely until the battery failsafe is triggered and Astro returns home automatically.

If these instructions are unclear or if you have any additional questions, you can learn more about planning in the AMC docs or contact us at support@freeflysystems.com.

Coverage

To get high-quality results, every area of interest in the map should appear in 5 or 6 overlapping photos. Obtaining this much coverage along edges or in corners requires that the area to be flown is larger than the area to be mapped. Also consider that if the gimbal is not pointing straight down (for crosshatch surveys and such), the drone will need to fly PAST areas that need to be seen in images because the image is looking in front of the drone.

USB Setup

The USB flash drive included will be formatted to work with Astro. In the event that you encounter issues or would like to use a different USB flash drive with Astro, follow the instructions in the USB formatting section. Be sure enough space is available; you will need at least 16GB for a single mission.

Included USB Flash Drive

Astro Map and the mapping payload both include a Samsung 64GB flash drive. If you want to replace or purchase additional flash drives, we recommend trying to get the same model as we have tested this drive thoroughly. It will also help our support team troubleshoot any issues you might encounter.

Camera Setup

Camera body and 24 mm lens settings

• Body Exposure Compensation Dial: 0, and the lock button engaged

• Lens Aperture ring: A

• Lens Focus switch: AF

AMC camera settings (tap slider icon below on-screen shutter button)

• Focus: Auto (infinity does work as well)

• Exposure Mode: Manual

• ISO: Auto

• Aperture: f/5 - f/11 depending on lighting conditions

• Shutter: 1/1000 or greater (can go as low as 1/500 but aircraft needs to slow down to prevent blur.

• Storage: USB Drive

Flight planning

Choose a survey flight path angle that minimizes the number of turns (or in other words, think about maximizing long, straight flight paths). For example, if surveying a complex next to a road that runs at a 30-degree angle, rotating the survey lines to match may reduce the maneuvering Astro has to do and will result in shorter missions and better pictures.

Rotate the survey entry/exit points to start and end at logical places. It is usually more efficient and safe to start at the furthest point from your takeoff location, as your mission will likely end closer to the home point when battery levels are most critical.

Use overlap and sidelap settings suitable for your processing software and output type. AMC's defaults (70%) are reasonable starting places, but reducing these values can allow faster flight and more area coverage. Lower front overlaps will allow Astro to fly faster in a mission, but be sure the value is acceptable for whichever processing software is in use.

Tips for Large Projects

Astro can cover areas greater than 200 acres in a single flight at 2cm GSD. Some tips for flying these types of missions:

• Uncheck the "refly at 90°" option at the bottom of the Survey settings while planning a mission. This will cause Astro to only fly over the ground in single-direction passes as opposed to a cross-hatch pattern.

• If possible, fly from the center of a large survey to reduce the distance between the Herelink and Astro. The maximum telemetry distance is shown in AMC during mission planning if you're at the takeoff location. Being able to have a line of sight to the vehicle at all parts of the survey is important for safety as well as maintaining a solid data link.

• Fly at 10-12m/s. The aircraft can fly up to 15m/s, but the flight time will actually increase if flying above 12m/s and result in a longer flight.

• A "typical" large area survey might have the following parameters: 12m/s speed, 120m altitude, 70% front overlap, 65% side overlap, and the gimbal angle pointing down (90°).

• Astro defaults to limiting the distance between waypoints to 900m. This is intended as a safety check to ensure that an accidental waypoint doesn't send the drone out of range to an unintended location. However, this may limit the length of a reasonable survey in some edge cases. This value can be increased by changing the parameter MIS_DIST_WPS. Do not set it larger than necessary to maintain the safety benefit.

Tips for Small Projects

Smaller areas can be covered the same as a large project, but usually higher detail is desired. In these cases, a crosshatch pattern can be used with gimbal pitch to get better detail on the sides of vertical objects. This gives better 3D reconstructions.

• Check the "refly at 90°" option at the bottom of the Survey settings while planning a mission.

• Set the gimbal angle to around 70 degrees to get better imagery on the sides of objects.

• Fly lower (60m or less) depending on the situation. Lower altitude will result in higher-density photos; just make sure that safety is the highest priority and that no obstacles intersect with your flight path.

• Make sure to fly well beyond the boundaries of the object being surveyed when the gimbal is tilted to ensure that it can be seen from all sides.

• Generally speaking, slower flights will provide more accurate results.

AMC on a computer

It's possible to plan missions and monitor flights from AMC on a computer or tablet. Here's the procedure to connect another device to the Herelink.

Esri Site Scan

Astro is integrated with Esri's Site Scan, allowing for a very clean end-to-end mapping process that we cover in the Site Scan section of our wiki. We strongly recommend using Site Scan if your primary use case for Astro is mapping.

Flying

From AMC Fly view, use the confirmation slider to begin a mission.

During a mission, you can take control of the aircraft pressing the Flight Mode buttons on the controller (Position, Altitude, and Manual). The aircraft will switch to the selected flight mode and begin responding to your commands.

Verify that the camera is oriented correctly (downward when taking photos and forward when landing to avoid ground strikes).

Verify that the aircraft is taking photos by looking for photo icons on AMC Fly view map or the incrementing photo counter on the live video camera control panel.

Landing

When the aircraft lands, do not immediately power down. The aircraft will automatically perform post-processing operations like creating the RINEX observation files. AMC will show a progress bar. When the process is complete, the drone may be powered down. The drone can be folded and moved while it is doing its post-processing, but it is suggested to disconnect ONE battery as an added safety measure. Do not disconnect the payload while the aircraft is powered on.

Post Processing

Astro Map output is compatible with modern stitching software that can accept normal JPEG EXIF Geotags. In general, if it can use the files generated by a DJI Phantom 4 RTK, it will work with Astro photos. Freefly has tested the following for compatibility:

• ESRI Site Scan

• Pix4D

• Drone Deploy

• Propeller.aero

High Accuracy Workflow

This section focuses on tools and techniques to improve accuracy.

Relative Accuracy describes the quality of measurements between points within a map (e.g. object size, shape, and separation). The map may not be aligned with the real world, but it is self-consistent (lengths of objects are accurate).

Absolute Accuracy describes the quality of measurements between points on a map and points in the real world.

GSD

Ground Sample Distance (GSD) is the photo or map's "resolution" typically given in units of distance per pixel, e.g. cm/px. GSD is the size of the camera's pixels on the ground.

Functionally, GSD is the upper limit of precision for measurements extracted from a photo/map/cloud/mesh. For example, if a measurement precision of 1 cm is needed, the mission should be planned so that GSD is 1 cm or less.

GSD can be chosen as a survey input in AMC's Plan tab, but it will adjust the altitude of the mission using the given overlap requirements. It is important that the operator verify the resulting altitude that AMC calculates is safe to fly.

Coordinate Systems

The cheapest accuracy available is in eliminating coordinate system errors. It's not always easy, but it is free.

Post-processing software is designed to accept input in a variety of coordinate systems, but each piece of software has its own peculiarities in handling coordinate conversion. Here are a few tips:

• Astro outputs photos geotagged in WGS84 latitude/longitude, and EGM96 elevation in meters. This is what is found on the USB stick plugged into the aircraft.

• When working with PPK, coordinate systems become much more complicated. The coordinate system the photos are in after PPK will be the SAME as the coordinate system used by the base station. For example, if the base station was placed on a pre-surveyed marker, and you know the coordinates of that marker in NAD83(2011) geographic coordinates, and those are what you enter as the base station position in the PPK app, then all the resulting geotags from the PPK app will ALSO now be in NAD83(2011).

• A common error is when the base station location is corrected using an online service such as OPUS. Those services accept the base station observation file and solve for the position of the unit with high accuracy. However, the reported position coordinate system may not match the desired output at the survey site. OPUS reports back in IRTF2014 and NAD83(2011). Use the base coordinates that apply to your site. If your site is not using any of those, Tools like NOAA's VDatumWeb can convert between them.

• The FreeflyPPK app or Precise Flight PPK app does not include vertical datum settings. (Look for these in a future version.) The resulting vertical reference will match the coordinates of whatever height is used for the base station.

Geotag Corrections

The photos created by the Mapping Payload are geotagged when they are stored on a USB drive (not the SD card in the camera).

Geotags are metadata attached to photo files that capture the camera's location in the 3D space and the direction vector of the camera when the photo was taken. These pieces of information allow post-processing software to quickly perform an initial alignment of the photos. More accurate geotags make processing time shorter and improve the quality of the output.

Astro will geotag the photos with whatever level of accuracy is available to the aircraft. The onboard GPS provides absolute accuracy down to 1-3 meters. The relative accuracy will be much higher, but it depends on the GPS constellation, mission duration (it drifts over time), and other factors.

The accuracy of GPS systems can be improved by strategies involving multiple receivers.

If a Freefly RTK Base Station is connected, the geotag absolute accuracy does not improve (unless placed on a previously known location), but relative accuracy is refined to the centimeter range.

Astro stores onboard GNSS observations and the geotag accuracy (both relative and absolute) can be improved further by post-processing after the fact. This process is known as "PPK". Freefly and Auterion both have apps that can correct the photos via PPK and improve their absolute accuracy to as good as 1-3cm.

PPK processing can be performed with a variety of base stations and software. The next section gives more detail.

PPK

The easiest way to increase absolute accuracy is to use a GNSS Base Station with Astro's free PPK Software. PPK Software uses GNSS Base Station output to improve photo geotag accuracy through a process called Post Processed Kinematic (PPK) correction. Accurate geotags give your post-processing software a better starting point, improving output map/cloud/mesh accuracy.

How accurate is PPK? Relative accuracy typically is less than 1cm. Absolute accuracy is more complicated:

If no other corrections are used (i.e. no GCPs) absolute accuracy is the same as that of the base station. PPK essentially solves position offsets by comparing the aircraft's position to the base station, so if the base station position is known globally accurate to 2cm, the resulting PPK geotags will be similar.

These are a few ways to determine base station location, ordered from highest to lowest accuracy:

• Place GPS base station precisely on a known ground control point survey marker using a high-accuracy tripod with tribrach. A survey pole and tripod can also be used, but accuracy might suffer depending on how accurately the pole in question can be leveled.

• Place the GPS in a clear view of the sky and leave it running for an hour or more. Then use an online post-processing tool such as NGS OPUS or Trimble Centerpoint RTX if you have a Trimble base station. This will take all the observations from the GPS and do its own PPK processing to determine the location of your GNSS unit very accurately. The downside is often having to wait hours or days for the underlying GPS data to be updated in OPUS before it will process your file. (Pay attention to the coordinate system that is returned)

• Average the position file generated by your GPS unit- if it's been stationary for over an hour, reasonable accuracy can be achieved, although GPS can vary slowly over many hours so this still may have sub-meter errors.

• Survey-in the GNSS; this usually integrates for a few minutes when it's powered on, then writes its averaged position to the RINEX headers. This value is better than nothing.

• Read out the instantaneous position of the GNSS after you've set it up and it has achieved a stable lock. This is the least accurate, and will only be accurate to GPS's normal accuracy of 1-3m.

An example PPK workflow:

1. Arrive at the site where you intend to fly.

2. Set up base station, ideally, on a known survey marker. Otherwise, find an open space with a clear view of the sky (to the best of your ability).

3. Start observation file logging on the base station. Many can be configured to start at power on, but it is usually worth checking that the base station is recording before takeoff.

4. Prepare Astro and fly missions.

5. When you are done, log into the base station and stop recording.

6. Download the RINEX files from the base station and put them on the USB drive from Astro.

7. Geolocate the base station. If it was on a known point, you're ready to go. If you are using an online processing tool, wait until the base station has enough data from nearby CORS sites to process (1-2 hours minimum), then get the processing report. Acquiring this report varies depending on your hardware and location, so consult the user manual of your base station for more info.

8. Use the FreeflyPPK app or the Auterion PreciseFlight app to post-process the photos.

9. Take the resulting high-accuracy geotagged photos to whichever photogrammetry tool you choose (ESRI sitescan, pix4d, DroneDeploy, propeller.aero, Agisoft, etc).

GCPs - Ground Control Points

Ground Control Points (GCP) are pre-surveyed points that are marked to be visible in aerial photos. GCPs are used by the post-processing algorithm to correct distortion and align the map with the real world.

PPK allows you to achieve high-accuracy maps that do not require GCPs. GCPs can require significant effort to survey and process. However, they tend to be the most accurate, even with poor initial coordinates in the photos.

GCPs can be used in a number of ways:

• A base station can be placed on a single GCP and used as high-accuracy positioning for PPK processing. This is the method that gives great results for the lowest amount of effort.

• A few GCPs can be used, one with the base station. This allows high-accuracy PPK, and the additional GCPs can be used as an accuracy check on the PPK results.

• a large quantity of GCPs (5+) can be surveyed and used in combination with or in lieu of PPK. This is the most costly as it requires surveying all the points, and then running the tagging process.

Maps using GCPs will generally be as accurate as the GCP can be marked in the photos and how accurate the GCP coordinates themselves are known (usually reported by your surveyor).

GCPs are used like this: Before flying, ensure that the mission will overfly multiple GCPs and ensure their clear visibility in aerial photos. After flying, enter GCP coordinates into your post-processing software. Use your photogrammetry software's workflow to mark the locations of the known coordinates in the photos. Then there will be a processing step. Afterward, you can overlay the GCP checkpoints and measure the distance from their coordinates to the marker in the output.

GCPs can be established by a surveyor, or with your GNSS base station.

• Propeller: https://www.propelleraero.com/blog/how-to-optimize-your-ground-control-point-placement/

Astro is compatible with Propeller Aeropoints.

To install the gimbal:

• Orient the gimbal under the aircraft so that it is facing forward and the Smart Dovetail is facing upwards.

• Slide the gimbal Smart Dovetail into the Isolated Dovetail receiver that is on the underside of the aircraft. Slide until you hear an audible click of the safety latch and the connector is fully seated.

• Close the dovetail locking lever until tight and the gimbal is secure.

To remove the gimbal:

• Open the dovetail locking lever so that it is loose.

• Hold the safety latch so that it is disengaged.

• Slide the gimbal dovetail towards the front of the aircraft to fully disengage from the Smart Dovetail Mount and remove the gimbal.

Latest gimbal firmware

How to check gimbal firmware

Gimbal firmware versions are also included in gimbal log files

Gimbal firmware release notes

v2.1.0

• Initial Release for OGI Payload

• Updated 75mm tuning for LR1 on Astro with large motors

v2.0.2

• Initial release for LR1 Payload

v1.7.2

• Change: baud rate to enable reliable parameter forwarding

• Bugfix: now handles mavlink forwarding turned on

This is a required firmware update for Astro's running firmware 1.6 or later. This gimbal firmware will only work on Astro FW 1.6 and later

v1.6.2

• Bugfix: Fixed the SD card corruption issue, preventing the gimbal from powering on

• New: Added tilt limits to mongoose of -90 and +30 degrees tilt

• Improvements:

  • Improved heading control

  • Calibration and process updates to improve attitude performance

  • Added GPS date time as supplied by Astro to log

v1.0.1

• Initial Release

Updating Gimbal Software

1. Download the firmware package.

   • Extract the .zip folder contents.

   • Open the extracted folder- the top level folder that you will need to copy onto the gimbal will be called "freefly". Do not copy the folder that states the firmware version.

2. To upgrade Gimbal firmware, connect the gimbal to a laptop using a USB-C cable.

   • The USB-C connector is located on the Smart Dovetail of the gimbal

   • Ensure the gimbal is not powered by the aircraft

   • The gimbal will show up on the computer as an external drive called "FREEFLY"

1. Open that drive and you will see a folder named "freefly". This is the current firmware file that you need to replace.

   • Delete this folder and replace it with the new firmware folder "freefly' that you downloaded in Step 1

1. Remove the USB-C cable from the gimbal and connect the gimbal to an Astro using the Smart Dovetail to power on the gimbal.

2. Insert 1 SL8 Battery into the aircraft and fully latch the battery, but do not power on the aircraft at this time.

3. Use a paperclip or small screwdriver to hold down the Firmware Load button on the gimbal- this button must be pressed and held for 10 seconds while powering on the aircraft.

   • This small button is recessed into the gimbal housing and is located next to the USB-C connector on the Smart Dovetail.

4. Power on the aircraft by double clicking the button on the SL8 battery.

   • Ensure that the Firmware Load button is held down during this time for 10 seconds while the new firmware is loaded onto the gimbal.

5. When firmware is successfully updated, the gimbal should stabilize correctly and video feed will show on the controller.

Camera Software

We have tested LR1 cameras on 1.00 FW. We do not recommend any updates to the camera as it may cause compatibility issues with Astro and AMC.

Gimbal Logs

With Astro off or with the gimbal removed from the aircraft, connect a USB-C cable between a computer and the USB-C port on the payload side of the dovetail. A drive will mount on your computer. The logs are located under "freefly\movi\logs".

Mapping Sample Data

The LR1 and A7R4 can easily be configured to perform inspections on power lines, wind turbines, and other infrastructure!

Gimbal Setup

For inspection use cases, we recommend using a long lens to maintain a safe distance from your subject. We have found that both the Sony FE 50mm F1.8 and Samyang 75mm F1.8 (LR1 only) work well.

After changing the lens, make sure to balance the gimbal, covered in this section:

Camera Setup

We recommend the following camera settings for sharp, detailed images:

All of these parameters can be setup in AMC, accessed by the 3 lines under the shutter button Additional settings we recommend:

• Focus: Auto or Tap-to-focus

• Focus mode: Center or Zone (if not using tap to focus)

• Overlay: Reticle

#protips

• Download the offline maps for the area you will be flying in

• Check the vibration isolators are in good condition before each flight

• Check the gimbal is balanced and the thumbscrews are tight

General Steps Before PPK Process:

If you are not able to follow these steps exactly, there is more guidance below.

1. Set up your base station (list of tested stations are below) and get it recording

2. Fly your mission with Astro, then wait for it to finish processing photos after landing

   1. Shutoff Astro

3. Pull USB-C stick, and insert into iPad (if accessing base-station data from iPad)

4. Go to Files app, browse to USB drive, and determine which folder has the files from this scan. i.e. folder 58

5. If using EMLID REACH:

   1. Open EMLID app:

      1. Stop logging all 3 logs (position, raw data, base correction)

      2. After they are zipped, download all 3 files to the usb stick in the same directory as the scan

Freefly PPK

Freefly PPK Desktop Application takes photos and GPS data generated by Astro during a Mapping mission, as well as data from a GNSS base station, and applies the Post-Processing Kinematics (PPK) algorithm to tag photos with highly accurate geotags.

Download the software from

Current PC Version: v1.1.0 - Released 08/2024

Current Mac Version: v1.1.0 - Released 08/2024

Table of Contents:

1. Compatible Devices, Download Links

2. Input, Output, Workflow

3. Debugging tips if you encounter errors

Compatible Devices

Operating Systems

• Windows PC - Tested on Windows 10

• macOS - Tested on M1 only

GNSS Base Stations

• Trimble R2,10,12

• Emlid RS2

• Generally, any device that can output RINEX (Observation and Navigation data files)

Input

• Output folder from High Res Mapping Payload.

• RINEX files (OBS and Nav Data files) from GNSS base station (that was actively recording GNSS data for the full duration of the time that the Astro mission was running).

• GNSS base station coordinate

  • Using pre-surveyed point as reference coordinate

  • Using Reference Network calculation (i.e. NOAA's CORS, Washington state's WSRN)

  • For very basic results, averaged value from base station rinex file

Output

Photos in PPK_Photos folder with corrected geotags.

Workflow

PRE-PPK CHECKS

1. As summarized above, to start PPK-ing your photos to get centimeter level geotag accuracy, you need to:

   • Complete an Astro Map mapping mission that writes photos, imagelog.json, *capture.obs, and *capture.json file into a mission folder (see Fig 1 below) into the USB-C thumb-drive. This is a simple and streamlined process, and you will generate this folder if you follow with the instructions in Astro Mapping Payload: Quick Map Workflow.

Fig 1. Here is what the mission folder generated by an Astro Map mission might look like:

• Have a GNSS base-station running and recording satellite data throughout the duration of the flight that can produce (Observation and Navigation data files). Grab the RINEX data files (usually ends with .<##>O - for OBS or .<##>P for NAV, sometimes just .RNX for both file types). If the file names are ambiguous, you can inspect the files and look at the first few lines to see if they contain the keywords Observation (for obs file) or Navigation (for nav file) data file. IMPORTANT - Ensure that the NAV data file is a "MIXED NAV" data file that contains nav data for all constellations.

1. Grab the Observation and Navigation data files (either individually) or the folder that contains them and place it into the Astro Map mission folder that contains the photos and the other mapping mission artifacts (imagelog.json, *capture.obs, and *capture.json).

Placing base station file into the folder shown below:

Fig 2. Placing base-station files into the folder shown above. The file types might be different

Pre-PPK Notes:

• Do not close any pop-up cmd prompt or terminal windows (this is due to the application running a subprocess necessary for PPK-ing)

• It's a good habit to check to ensure that the original geotags on a couple of the photos somewhat correspond to the image location.

  • To do this: Use an exif inspection tool, grab the geotag from an image, search up coordinates on Google Earth, compare to see if the photo content somewhat matches up with coordinates on Google earth

  • If the images do not align, it might be a good idea to get the flight log (.ulog) file from the mission and use the Use ULOG workflow in the Freefly PPK app to get proper alignment.

Freefly PPK Processing:

1. Open FreeflyPPK application.

2. Click on browse at the top to choose the Astro Map mission and select the folder.

3. The application should browse the folder and search for the requirements and automatically fill in all of the requirements.

4. If you know where the base station ground coordinate was, then enter it. This can be done using a GNSS reference network processing provider (i.e. in Washington state you can use Washington State Reference Network, in the U.S. you can use NOAA CORS and upload your base RINEX files) You can use either DMS or Decimal coordinates (Click the DMS Coordinates check-box.)

5. If you don't know the base station coordinate, by changing from MANUAL on the drop down to AVERAGE FROM OBS you can get a very rough estimate of the base station. It applies single point positioning to the base station RINEX files. The averaged postion will be displayed on the status bar once the project processing begins.

6. Go ahead and select how high you placed the receiver from the ground (usually your base station tripod pole will have a marking to let you know). The application will take care of antenna phase center variation based on the base-station type detected from the base-station OBS file.

7. If you are rerunning the same mapping mission folder, checking the Overwrite Output check-box will overwrite the output folder with the current processing output. It is set to overwrite on default since the application can otherwise keep on making copy of the photos and take a lot of space on your computer. If the Overwrite Output check-box is not checked, then the application will rename the previous folder and save the output of the current processing to PPK_Photos. *TIP: you want to explore output with multiple settings (i.e. different base station coordinates or base station files), it might be beneficial to rename the PPK_Photos folder to something more useful*

8. Once all of the project requirements are met, you will be able to click the Process button and the application will correct the geotags on your photos after it conducts PPK on them. It will output them into the PPK_Photos folder and keep your original images untouched. Monitor the output and ensure all or most of the photos are tagged with Q=1 quality. The Q value corresponds to the quality of the corrected geotag. Q=1 is great. Q=2 is ok. Anything higher is not accurate.

9. Once your images are PPK-ed, you can use a map generation provider like ESRI Sitescan (which is recommended and we have tested on) and upload the images from the PPK_Photos folder. In the Advanced Processing Settings:

• If you completed the PPK process with a surveyed point or reference network, use the +/- margin of error they provided to you in the base station location for the geolocation accuracy.

• If you use the AVERAGE OBS FILE option in the FreeflyPPK app, use +/- 100 cm. Note that it is not recommended to run AVERAGE OBS if you want high fidelity maps.

Debugging Tips:

• Known Issue: If drone is flying below sealevel or drone is flying at negative altitude in the chosen base-station coordinate system, then the application will fail the geotagging process (status list error). This will be fixed in a future release.

• If you entered base station coordinates in Degrees, Minute, Second format, make sure you use the correct sign. i.e. If the coordinate you are entering is 122° 09' 7.93789" W, on Freefly PPK, you should enter -122 09 7.93789

• If the correct base station file is not be detected correctly, remove all of the base files from inside of the project path folder. Then, individually go into modify the selected base and rinex files using the modify buttons below the status box. Check content inside the base files for "Observation" and "Navigation" to ensure you are choosing the correct files.

• One of the first debugging things you can do is to close the application and reopen it. More advanced users can go in and delete the .ppk_history file in their home directory to remove application cache file.

• Check to see if the rtkdata_events.pos in the working directory has been generated properly. If everything looks good there, but there is an issue with photo tagging. (i.e. "Issue with abc.jpg tagging" alert, then there is likely an error with your filesystems (see common file systems error).

• Common file systems errors: Not enough space on your hard drive. Make sure the project path has plenty of space. A bunch of 25MP images can fill up your storage device quickly. Again, as previously mentioned, you will get much better performance if your project folder is in your local hard-drive instead of an extenal drive.

• If you have any issues with Freefly PPK and have questions for Freefly Support team, it would help if you sent as many of your files as you are able to (i.e content of working directory, capture.obs, sequence.json, and base-directory folder). It helps to include a screenshot of the application during an error, but ensure you expand the status list so that the whole error is visible in the photo. Since this is our first release of Freefly PPK software, we are actively working to improve the user experience based on feedback.

Precise Flight

Precise Flight by Auterion is an alternative option for the PPK workflow. It can be downloaded from the App Store.

Compatible Devices:

iOS devices - primarily useful with iPad

Precise Flight by Auterion Workflow

• Set up base station and get it recording

• Fly mission with astro, wait for it to finish processing photos after landing

  1. Shutoff astro

• Pull usb stick, and place into ipad

• Go to files app, browse to usb stick, and determine which folder has the files from this scan. I.e. folder 58

• Open emlid app

  1. Stop logging all 3 logs (position, raw data, base correction)

  2. After they are zipped

  3. Download all 3 files to the usb stick in the same directory as the scan

• Extract data

  1. Go to files app

  2. Browse to the folder with the photos in them

  3. Click once on the zip file with the emlid raw RINEX data in it to unzip

  4. It will create a folder in that directory

• Delete old data?

• Go to preciseflight app

  1. Select base station folder, will be the RINEX directory inside of the flight folder

  2. Select the vehicle folder- it is the folder with your mission number such as “58” that has the photos in it

  3. Decide if you want to set base position manually, enter as desired

  4. Enable compensate camera offset

  5. Hit process, wait the 30-60 seconds for processing

  6. When processing is complete, the files will be located in the Auterion Precise Flight app on the ipad (not on the USB stick).

  7. When working properly, Sitescan app can be pointed at that folder to upload the photos

  8. I’ve been using files app to copy the PPK’d photos into a new folder on the usb drive and then transferring to computer.

Recommended USB-C Flash Drive

• The LR1, A7R4, and OGI Payloads ship with this USB-C flash drive.

• We recommend a USB 3.1 drive with a write speed above 50 mb/s.

USB Setup

The USB flash drive included will be formatted to work with Astro. If you encounter issues or would like to use a different USB flash drive with Astro, format using the instructions below.

Formatting the USB Drive

Mac

1. Open Disk Utilities and click on the flash drive in the sidebar.

2. Select the Erase option at the top of the window.

3. In the Format dropdown, select MS-DOS FAT and click Erase.

4. Once that completes, click the Eject arrow near your flash drive on the sidebar.

Windows

1. Open This PC to show all connected drives.

2. Locate the USB drive you want to use with Astro, right-click on the image, and select "Format...". A small window should open.

3. Select ExFat under the File System dropdown and click Start.

4. Once that completes, right-click on the USB drive in This PC again and select Eject.

Tilt Control

The payload's tilt rate scales with zoom. This means that as the digital zoom level is increased, the gimbal's tilt rate will decrease to provide pointing control.

Yaw/Pan Control

By default, the aircraft's yaw control is unaffected by the camera's zoom level; however, zoom rate scaling can also be applied to yaw/pan through Slow Speed Mode.

For even more control, the global yaw rate of Astro can also be adjusted if desired. The default global yaw rate of Astro is 75 degrees/second.

• The max yaw rate can be adjusted by going to Advanced Mode (tap the Auterion logo in the upper left-hand corner seven times). Then click on the Auterion logo again and click through Vehicle Setup -> Parameter -> MPC_MAN_Y_MAX. The units are in degrees/second.

Slow Speed Mode

Slow Speed mode is a togglable flight mode that affects the sensitivity of the aircraft's yaw when the camera is zoomed in.

• Slow Speed mode can be toggled on and off when Astro is in Position mode. It's active when the icon is lit, and you view the video stream.

  • Slow Speed mode will automatically deactivate when viewing the IR stream

  • Slow Speed mode is turned off by default

The Astro Isolator is recommended for all payloads, including the LR1, A7R4, Wiris Pro, and OGI Payload.

• The Astro Isolator is available in our store. Instructions on how to install the isolator on Astro are below:

This isolator has the Smart Dovetail connector attached and allows swapping between the OGI Payload, LR1 Payload, Wiris Pro Payload, A7R4 Payload, and other payloads that use the Smart Dovetail standard.

Check all the dampers are in good condition before each flight, as these can wear out over time. We recommend replacing all dampers on the isolator every 6-12 months. 30A durometer damper replacements are included in the Astro Isolator Kit and are available through our store: