Mapping Payload Hardware Overview

Astro Map is a turnkey Freefly drone that includes the Mapping Payload for enterprise mapping workflows.

• Learn more about the Astro aircraft here.

• The Mapping Payload consists of a Freefly gimbal with an integrated Sony Alpha 7R IVA camera. It is developed for use with Astro and other vehicles that use the Freefly Smart Dovetail and the Pixhawk Payload Bus standard.

Gimbal Packing Foam

The foam we designed is the safest way to pack and ship your mapping payload. However, it can be cumbersome to figure out how to attach it for the first time. Here is a #protip video showing you how we do it.

Installing/Removing the Gimbal from Astro

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.

​The Freefly Mapping Payload is Sony's 61-megapixel Alpha 7R IVA camera integrated with a Freefly gimbal. It ships with a 24 mm lens, and several other lenses are supported.

The payload is optimized for photogrammetry. It also supports inspection and scenic photography.

Mapping Sample Data

Workflows

Quick Map Workflow - Make a map quickly! These considerations are relevant to all mapping workflows.

High Accuracy Workflow - Tools and techniques (like GNSS Base Stations and PPK software) to improve accuracy.

Inspection / Scenic Workflow - Unique aspects of shooting inspection or artistic photos.

Video Workflow - Adapt your a7R-IV to record video footage.

Advanced

Camera Settings - How to change camera settings within AMC, as well as the settings we recommend for most use cases.

Efficiency Tips - How to increase efficiency and work in a wider variety of scenarios.

Aircraft Battery Changes - How to switch batteries efficiently between flights.

Quick Map Workflow

Flying

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

During a mission, you can take control of the aircraft by simply moving the sticks. The aircraft will switch to Position Mode, halt, and begin responding to your commands. Alternatively, you can press one of the physical Flight Mode buttons on the Herelink, like the Position or Return buttons located below the screen.

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 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 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 meter. 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 for determining 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+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. Setup 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.

Inspection Workflow

For inspection, we recommend these settings:

• Camera body setting > Focus Mode: Center

• Camera body setting > Exposure Metering Mode: Center

• AMC setting > Grid: Reticle (which approximates the focus area)

• AMC setting > Focus: Auto

Video Workflow

Astro Map is primarily intended for photos, but with some minor modifications it can be used to record video.

Once these settings are changed, you can switch between taking images and video footage using this button in Photo Mode:

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 Herelink before you go to a site with no internet, download them while the Herelink 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 ɑ7R IV - 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

Camera Settings

AMC provides control of these settings in flight by pressing the icon on the right of the screen while in Photo Mode:

AMC will override these camera body settings:

• Shooting Mode dial, if set to P.

• Exposure Compensation dial, if set to 0.

Other camera body controls and menu options will be honored. For example:

• Focus Mode (e.g. wide, zone).

• Exposure Metering Mode (e.g. spot).

• Exposure Compensation dial, if set to non-0 value.

File type: JPG and RAW are available.

Efficiency Tips

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.

Known issue: Photos aren't exactly equally spaced in the flight direction causing some small variation in spacing. This might require a slightly larger forward overlap setting to ensure there is enough overlap in every case.

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.

Aircraft Battery Changes

For normal operation, it is recommended to unplug both batteries, and then connect a new set for each flight. However, the aircraft can hotswap batteries to allow for the continuation of a mission that requires more than one flight. To hotswap, do the following:

1. Disconnect one of the discharged flight batteries from Astro.

2. Replace the removed battery with a fully charged pack.

3. Press the power button on the battery twice and ensure it turns on and says "hotswap" on the new battery's LCD screen.

4. Disconnect the second discharged battery.

5. Replace the second removed battery with a second fully charged pack.

6. Power on the second battery the same way, and ensure both are powered up.

7. Continue mission after the post-processing for the previous flight has been completed and there is no longer a progress bar on the Herelink.

AMC on a computer

Saving Photos to Camera and USB Simultaneously

Changing a7R-IV Settings

Astro remembers the settings that you can change within the AMC software. Next time you power on the system and when the camera establishes a connection with Astro, Astro will set these settings.

If a setting is not exposed in the app, we are most likely not overriding this setting. In order for these settings to be changed and saved even if the unit is powered off, follow the below procedure:

• Using the wheel on the Herelink, tilt the gimbal/camera down at an angle so it's easier to access the buttons on the camera.

• Using the menu or “fn” buttons on the camera, change the desired settings.

• Turn the camera power off by using the rotary switch on top of the camera.

• Wait 10 seconds. The camera takes a while to save settings to its own memory.

• Power the camera back on. Confirm that the settings that you changed have persisted.

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 https://freeflysystems.com/support/astro-support

Current Version: v0.0.3-beta - Released 06/06/2022

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 x86_64 and M1

  Note, for the current app version, you will need to override current mac security settings through instructions provided here: https://support.apple.com/en-us/HT202491

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.

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.

Smart Dovetail Isolator Upgrade Kit

Freefly offers a Smart Dovetail Isolation Upgrade kit to upgrade your Base Kit cheeseplate isolator to an isolator that is compatible with the Freefly Mapping Payload.

• If you buy an Astro Map, this isolator is already installed.

• If you buy a Mapping Payload, you will need to upgrade your Astro Base with this Isolator Upgrade.

To install this onto your aircraft, use the provided M3x8mm Button Head screws to install the isolator as follows:

• Install the Isolator Upgrade Kit onto the lower chassis so that the cable is facing the rear of the aircraft.

• Attach the isolator to the chassis using the 4x M3x8mm BHCS.

• Attach the safety lanyard to the lower chassis using 1x M3x4mm BHCS.

• Connect the Smart Dovetail connector to the IO panel on the underside of the Astro chassis.

Updating Gimbal Software

1. Obtain the provided new firmware package. This will be in a .zip folder format.

   • Extract the .zip folder contents. The file that will be provided will likely be titled with the firmware version like "Mapping Payload Firmware 1.X.X"

   • 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 Mapping Payload 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"

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

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

5. 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.

6. 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.

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

Resetting Camera to defaults for Astro Mapping

Changing Camera Settings

Here's an example video of the camera settings being changed (switching from JPEG to RAW, in this case).

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".

Balancing Procedure

• Loosen both fasteners in the camera hotshoe as well as the ¼-20 fastener with the washer so the camera is free to slide forward/backward.

• Hold the gimbal by its Pan/Roll arms and ensure the tilt motor can spin freely.

• Shift camera forward/backward in its slot until the camera does not tip up or down when it is positioned horizontally and released.

• To ensure the camera is very well balanced, test pointing the camera ~30 deg up/down; a well balanced camera will also not move in either of these two positions.

• Once the camera balance is correct, tighten the ¼-20 fastener as well as the two fasteners on the hotshoe.

Calibration Parameters

This is a set of example calibration values for the camera and lens system. Each lens is slightly different, but these values are good initial values if the software in use can't solve them directly.

Sony Alpha 7R IVA with Sigma 24 mm lens at F/5.6

Recommended USB-C Flash Drive

• The Astro Map and Mapping 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. In the event that 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.

Performance

The Mapping Payload's high pixel count allows you to cover a large amount of area quickly at low resolution, or collect very high-resolution imagery at lower altitudes. Approximate GSD, coverage per flight, and expected altitude are listed below for reference. This is based on a 70% forward and 65% side overlap, single pass (no crosshatch).

A single Astro flight with the Mapping Payload is typically 25 minutes. The exact time depends on the survey area's geometry, the number of turns required, and the flight speed, as well as environmental factors such as wind speed and direction. Note that the time presented in AMC is an estimate, and not adding return or transit waypoints may affect its calculation. A good rule of thumb is to aim for an AMC-calculated flight duration of 22-23 minutes. This should allow the flight to complete and return before hitting the battery reserve.

Camera Body

Sony Alpha 7R IVA (model ILCE7RM4A/B)

Weight

Astro's maximum payload weight is 1500 grams.

Gimbal

Lenses

We're currently in the process of testing more lenses, but we have no announcement for when we'll give an official endorsement.

Lens selection in AMC only matters for mission planning calculations (overlap, photo trigger, etc) and for infinity focus to work properly.

If you plan a mission with a non-standard lens, make sure that the correct lens is selected in the Survey section of the Plan screen. If your lens isn't on the dropdown, you can enter the details manually by selecting Custom Camera instead of a specific lens.

When changing lenses, select your lens from the Focal Length dropdown in Camera Settings found in the camera settings.

If your lens isn't on the dropdown, pick any lens from that menu and use auto-focus.