GPS and Sonar Data Collection for Sea Profile Reconstruction

Sammanfattning: The depth information on today’s nautical charts are often inaccurate. This is due to the fact that the data used often is taken from measurements done in the late 1800’s using contemporary methods. With the increasingly widespread use of chartplotters (a marine GPS unit which contains a nautical chart), especially in recreational boats, this has become a big problem.This project aims to receive and process data from such navigation equipment. The data is processed and transmitted wirelessly to a remote server were the data is used to update current nautical charts. This allows multiple users to collaboratively improve their current navigation possibilities.A test unit is built using a small linux computer, the Raspberry Pi. The test unit is also equipped with a marine GPS receiver, Garmin x18-5Hz, communication through the serial NMEA interface often used in these applications. As a proof of concept is the unit also equipped with an air pressure sensor, connected through I2C. The current air pressure is calculated to its corresponding altitude, resulting in a simple method for on-land measurements. A way to automatically calibrate offsets in GPS receiver/echo sounder position is developed and tested using the test unit.The test unit is capable of combining GPS coordinates and altitude data and sending it to a remote server. Small changes have to be made for the unit to be compatible with multiple GPS recessives and echo sounder. Further development is also needed for multiple users to simultaneously be able to use the system. It is proven that the concept of GPS and sonar data collection is possible for sea profile reconstruction.