Geode appears to be inaccurate in good conditions

28 Jan 2021

Just for reference, details regarding the accuracy of the Geode GNSS receiver are provided starting at the following web page.

Geode accuracy explanation and demonstrations

Data collected using the Geode may appear to be inaccurate for several potential reasons. One reason is the method being used by software applications (apps) to connect to or retrieve data from the Geode, similar to as detailed at the following web page.

Accessing GPS using Location Service vs Direct Connection

Another reason is when a user is unknowingly trying to compare a real-time GPS position or recently recorded data to previously recorded data (or background layers/imagery) that is using a different map system (datum, coordinate system, projection, etc.). One common method to tell when this has occurred is when all data points are (for the most part) offset (inaccurate) by the same amount in the same direction. For more details, see the following web page.

Datum of GNSS (GPS) receivers

As long as the user makes sure that all of their data, both new and old, are using the same datum, then it should all work and be comparable. It is easiest to just pick a datum from the beginning before collecting any data, and then use that datum from then on so no conversion is needed later.

As mentioned, usually you choose the datum / coordinate system / projection of your project in the field data collection software before you go out into the field to collect data. Often the software will automatically perform datum transformation when recording the NMEA data from the GNSS/GPS receiver so it matches the project. Because of this, most users don’t even know or care about the original format of the NMEA data from the GNSS/GPS receiver.