Best Practices for GNSS Data Collection with Bad Elf Receivers

Best Practices for GNSS Data Collection with Bad Elf Receivers

Best Practices for GNSS Data Collection with Bad Elf Receivers

Introduction

High-quality GNSS data collection is essential for accurate positioning and successful projects. This article outlines best practices to ensure you get the most out of your Bad Elf GNSS receiver.

Planning and Preparation

  1. Define Your Goals: Clearly define the purpose of your data collection and answer questions such as:
    1. What level of accuracy do you need? 
    2. Which features do you need to collect? 
    3. Which attributes do you need to record?
    4. Will you be outside of cellular coverage? 
    5. Will you be in a high multi-path location? 
Notes
Keep in mind that vertical accuracy is up to twice the value of the reported horizontal accuracy.  Connecting to a real-time network using RTK will drastically improve your accuracy.
  1. Charge Your Device: Ensure your Bad Elf receiver and any connected devices (phone, tablet) are fully charged before heading out. Consider storing a portable power bank for backup.  The Bad Elf Flex Mini has up to 24 hours of battery life, while the Bad Elf Flex has up to 12 hours.
  1. Update All Software and Firmware: Having the most up to date software is key for a successful survey.  This includes the:
    1. Bad Elf Flex app software
    2. Bad Elf receiver firmware
    3. Phone firmware
    4. Data collection app software 
  2. Test in a Controlled Environment: Before collecting data at your survey location, test both your Bad Elf receiver and the data collection app you intend to use.  Ideally, this is done at a point with known coordinates, such as a survey monument.
  1. Check Network Compatibility: Ensure your Bad Elf receiver is compatible with the GNSS correction service you plan to use.
Notes
The Flex Mini is only compatible with networks sending multi-signal messages (MSM), only found with RTCM 3.2 or greater.  
Notes
The Flex is compatible with all RTCM formats (not CMR).

  1. Offline Preparation: Keep in mind that RTK will not be available in areas without cellular service.  In such areas, the Flex will offer submeter accuracy offline, while the Mini will be accurate to 3-6 feet.
    1. Consider downloading offline maps for the area you'll be working in as well. 
Notes
The Flex is able to be used as both a base and a rover to achieve survey-grade results offline, using radios to broadcast and receive corrections.
  1. Configure Settings on Bad Elf Flex App:  Check the Bad Elf Flex app to verify elevation settings are correct and your RTN login credentials are valid.

  2. Avoid 2.4 GHz Mobile Hotspots When Possible: Wi-Fi creates Bluetooth interference due to being the same frequency.  Consider changing your hotspot settings to 5GHz.

Setting Up Your Bad Elf Receiver in the Field

  1. Connect a Phone via Bluetooth: Make sure the Bad Elf is paired and connected to your phone or tablet.  Any paired phones will connect automatically. 
Notes
Multiple connections can hamper stability.  
  1. Wait for a SBAS Fix: If the device hasn’t been used recently, this could take up to 10 minutes.

  2. Select Bad Elf as Location Provider: If the app or mock locator you’re using allows you to choose the location source, select your Bad Elf receiver.

  3. Set Antenna Height: Setting your antenna height properly adjusts the recorded elevation from the elevation of the receiver, to the elevation of the ground below.

  4. Open the Bad Elf App and Stream RTK Corrections (optional): Launch the Bad Elf Flex app on your connected device and follow the on-screen checklist under “Correction Mode” to stream real-time corrections.
Notes
Extreme mode, internet, and a RTN login is required. Please see Choosing the right RTK Network for more information
  1. Configure Coordinate Transformations (optional): Especially when using a RTN, transforming your coordinates from one datum/projection to another may be necessary.
NotesIdeaFor ArcGIS Field Maps settings including datum transformation via profile see Configuring ArcGIS Field Maps.

Data Collection Techniques

  1. Clear Sky View: For optimal signal reception, aim for an unobstructed view of the sky. Keeping the receiver away from your body and the ground by using a survey pole or other mounting solution will minimize multipath and tilt errors.
Notes
If your points are in a high multi-path location such as underneath power lines, in a downtown urban canyon, or under dense tree canopy, consider pairing a Bad Elf Flex with a laser rangefinder to record point offsets instead.
  1. Stable Position: Hold your receiver steady and vertical during data collection. Avoid tilt or movement, as this affects accuracy.

  2. Verify Accuracy and Fix Type: Ensure the displayed accuracy is stable and meets your project requirements before recording a point.

  3. Metadata Recording: Where possible, record metadata alongside your GNSS data. This can include details like accuracy, time stamps, fix type, etc. Metadata helps with data interpretation and analysis later.

  4. Point Averaging: We recommend using a point averaging duration of at least five seconds to maximize accuracy when possible. 

After Data Collection

  1. Export Data: Depending on your data collection method, you may need to download data logs from your receiver or export them for post-processing.  If the app allows it, ensure the proper datum, projection, vertical system, and export format is defined.

  2. QA/QC: Reference your metadata before leaving your survey site to ensure all required features are saved and the accuracy meets your requirements.

  3. Convert Formats:  Depending on your intended goal of the project, it may be necessary to convert file formats or schema.

  4. Wait for Static Post-Processing (Optional): If post-processing static observations, utilize compatible software like OPUS, CSRS-PPP, or Trimble Business Center after 24 hours have passed to achieve survey-grade to decimeter level accuracy.

  5. Transform/Project Coordinates (Optional): If your data collection app did not perform the required transformation in real-time, use a tool like ArcGIS Pro, Blue Marble Geographic Calculator, HTDP, NCAT, or others to convert them.

Additional Tips

  1. Point One Navigation Trial: Every Bad Elf receiver comes with a free trial of Point One Navigation, an international RTN.  You can use this to test how RTK will work for you, and can also use this app to see if there are public networks in your area.

  2. Review the Knowledge Base: Explore the Bad Elf Knowledge Base (https://badelfllc.zohodesk.com/portal/en/kb) or our Youtube channel for additional resources, troubleshooting guides, and best practices specific to your Bad Elf receiver model.

  3. Troubleshooting: If you run into any issues:
    1. Restart Bad Elf and phone.
    2. Test receiver in area with great sky-view completely free from overhead obstructions, while elevated off the ground.
    3. Clear all Bluetooth pairings on phone and Bad Elf and re-pair
    4. Verify only one Bad Elf is connected to only one phone
    5. Update all software and firmware
    6. Turn off mobile hotspot, or change to 5GHz
  4. RTK:
    1. Verify GPS fix
    2. Check internet connection
    3. Verify login credentials
    4. Try multiple mount points
    5. Verify coordinate transformations
    6. Eliminate multipath error from overhead obstructions
Notes
Record a track log to analyze and identify problems. See this article for more information.
  1. Contact Support: If you have any questions or encounter issues during data collection, feel free to contact Bad Elf Support at support@bad-elf.com with screenshots for assistance. We're happy to help!
By following these best practices and utilizing the advanced capabilities of your Bad Elf GNSS receiver, you can ensure high-quality data collection for accurate results in your projects.


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