Central Research Question and Purpose

This project aims to enhance the accuracy of water level measurements by embedding a Global Navigation Satellite System (GNSS[ST1] ) module in the instrumental package. to achieve self-surveying elevation measurements within an error margin of 1 cm. This improvement is essential for applications requiring precise elevation data, such as vertical land motion detection, sea-level rise measurements, and flood prevention.

Scholarly Context

Understanding current and future coastal and inland flood risk requires accurate data to support scientific modeling and analysis.  Current elevation surveying tools [ST2] offer high accuracy but are expensive (~$30k for a leading commercial brand).  By leveraging inexpensive GNSS technology and software-based post-processing (<$500), this project seeks to provide a more cost-effective and scalable solution while maintaining a high level of precision and accuracy. Reducing cost allows for more dense sensor networks, enabling the acquisition of a vertical elevation time series, thus improving the assessment of locally varying processes (such as subsidence or wave action).[ST3] 

Methodology

The project involves upgrading the GNSS module of the water-level system and conducting a field test at a known survey point to validate the accuracy of the elevation readings. Precise Point Positioning, a software-based post processing technique, was employed to improve the GNSS solution point accuracy. The hardware and software were designed to be robust, modular, and easily scalable to support a wide range of field deployments compared to the narrow scope for current surveying instruments.

Conclusions and Expected Results

The field tests that were conducted this past summer yielded a sub 3 cm error. To potentially further increase the accuracy, the deployment time can be increased from 24-hours to a week. Future work includes an integration of the GNSS technology with radar and ultrasonic distance sensors to allow for concurrent tidal measurements.