Base Station Availability
Overview
GRYFN systems have an integrated GNSS which collects highly accurate positional data throughout UAS remote sensing operations. This GNSS-INS data allows ~2-5cm georeferencing accuracy of image and point cloud reconstructions. While the GNSS data is collected during the flight, it must be refined in post-processing, leveraging satellite ephemeris data and reference stations to maximize quality and accuracy.
When post-processing GNSS sensor data, base station availability nearby the data collection site must be considered. NOAA provides data to Continuously Operating Reference Stations (CORS) for GIS professionals, engineers, and other positions that would benefit from increased positioning precision. When post-processing GNSS data, a few options are available to users for correcting their GNSS data:
Single Base
When a single reference stations is available < 20km from the rover location, that station can be used in trajectory processing for high accuracy solutions.
Virtual/Network Base
When there is not a single reference station within 20km of the rover, but there are several reference stations within 70-100km of the rover, network processing modes, also referred to as a virtual reference station, can be used to provide similar results as a single base.
Each GNSS-INS solution will approach network processing with slight differences. Linked below is a resource from Applanix further describing their implementation.
If the minimum number of reference stations required for virtual reference station processing are not available within the baseline limits, users have two options: deploying your own base station, or using *satellite-based correction methods.
User Operated Base
Users may choose to deploy their own base station at or near the rover for use in post-processing corrections. There are many solutions available, ranging in cost, accuracy, and ease of use. Two common examples are the Trimble R12 and Emlid Reach RS3.
User operated base stations require significant integration time in the field, often requiring up to an hour of data collection pre- and post-flight, but allow users to accurately and precisely process GNSS data in remote locations without access to permanent reference stations.
Satellite-Based Corrections
Some manufacturers provide base station-less satellite correction methodologies that may provide similar trajectory solutions to permanent reference stations. These are often locked behind various licensing tiers. Check the details of your GNSS processing license to see if this approach can be used in your environment.
Base Station Maps
NGS Base Station Map
For a list of CORS stations available in the US, please visit the NGS ArcGIS map. Use the measure tools from the survey area to pinpoint distances from the nearest base stations. See recommendations in the single base and virtual reference sections below regarding maximum distances from base stations to ensure proper processing.
SBG Global Base Station Map
For users with an SBG GNSS, visit your My-SBG-Systems account, select GNSS Base Stations from the left side menu. Dark blue circles indicate areas compatible with Single Base processing. Areas shaded by light blue indicate areas compatible with Virtual Reference Station processing.
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