, , ,

External GPS sources for Mappt Part 2: Mapping in the Field with RTK GNSS (survey-grade GPS)

mappt-rtk-gnss

In our last post we covered how to configure your tablet or phone to receive an external GPS signal via Bluetooth.  Here we share our experience of linking up Mappt with survey-grade RTK GNSS (Real Time Kinematic Global Navigation Satellite System) to achieve centimetre-level positional accuracy.

 

Utilising RTK GNSS and Mappt for centimetre-level positional accuracy

Utilising RTK GNSS and Mappt for centimetre-level positional accuracy

Achieving Survey-Grade Positional Accuracy with Mappt

Joe user asks, “Hey how can I achieve high positional accuracy with Mappt?

The short answer is, “Bluetooth to an RTK GNSS to achieve centimetre level accuracy“.

What’s GNSS?

GNSS, is the collective term for all satellite positioning systems which includes GPS (USA), BeiDou (China), GLONASS (Russia), Galileo (Europe), IRNSS (India), and QZSS (Japan).  Phones, tablets, and survey-grade systems use satellites from multiple positioning systems, thus we’re referring to these systems as GNSS (rather than GPS).

The Benefits of Using Mappt in conjunction with RTK GNSS

Mappt’s flexibility and onboard functionality helps users achieve the full benefits of high accuracy RTK GNSS while in the field.  For example when using Mappt in conjunction with RTK GNSS, users have in-field access to these mapping tools;

  • Locate and save point features with unlimited attributes
  • Thematic Mapping gives users the ability to colour code mapped information while in the field
  • Layering of data types to achieve hierarchal data structure and visualisation
  • Interactive functionality (exclusion & inclusion zone warnings) improving field safety
  • The ability to display web-based aerial/satellite imagery and other GIS information such as WMS, WMTS, & WFS
    • With a data connection, this data is continuously updated as you move to new areas
  • Offline display of high resolution aerial and satellite images (ECW, JP2)
  • Multi-user data capture & updates using MapptAir.

RTK GNSS Gear

In our previous post we detailed how to configure your mobile device to receive location information via Bluetooth.  Thanks to Mangoesmapping and Ascon Surveys both for their technical support and equipment (on loan) used to complete our trial.  We found the Emlid Reach RS RTK GNSS units (available from Mangoesmapping) suitable for this trial.

Our Field Experience

The following data was acquired in less than one hour (including setup and pack down of the RTK base unit and survey pole mounted rover unit).  Data collection in this small urban bushland was on-the-fly as point types were added as deemed necessary.  Points types collected included kerb locations, footpath limits and walking tracks.  Point types were added to our field form as necessary thus the list of point types was added to as new elements were observed.  *To save time, a dropdown list of point ID’s can be created prior to leaving for the site.  In the limited time spent onsite, three point IDs were all that was necessary.  We also utilised the geotracking utility to map in the trails crossing the site as well as to create a geofenced area at the park’s centre.  Lastly we tested Mappt’s geofence alerts feature by entering and exiting our geofenced area.  Have a look at this video showing how it works.

Mappt mobile GIS data gathering using RTK GNSS at Signal Hill, Belmont, WA

Mappt mobile GIS data gathering using RTK GNSS at Signal Hill, Belmont, WA

What we took away from the experience.

It was a simple step to download all data gathered to shape files and import them into QGIS.  We mapped in such features as the back of kerb, footpath limits, and bush tracks.  RTK GNSS units have the ability to validate/qualify positional information with an audible “Fixed” to indicate that positional information is within your specified accuracy.  Likewise when the positional information is below spec an audio warning “Float” will alert users that possibly more time at that location is needed to gain a fixed position or that trees or buildings are hampering satellite reception.  Our recommendation is to have this activated on your RTK GNSS receivers to eliminate collecting data of low positional uncertainty (occurs in areas of high tree cover and when adjacent to tall buildings) .

QGIS map showing GIS data gathered using RTK GNSS and Mappt

QGIS map showing GIS data gathered using RTK GNSS and Mappt