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NMEA Generator is an open-source drawing tool for generating GPS logs in NMEA format. Its primary purpose is to make it easy to draw a path representing a person walking or driving around while carrying a GPS device which measures their current position at regular time intervals (e.g. once per second). After the path is drawn, its representation as a sequence of NMEA sentences can be generated and downloaded as a text file.
The "Add point" tool is selected by default when the NMEA Generator is started. When you click on the map using this tool, a point is added to your path at the location you clicked on.
A point represents a position measured using a GPS device being carried around. The time elapsed between two consecutive points is always the same and equal to one second by default, but this can be changed under "Global settings".
To delete a point, select the "Delete point" tool and click on the point you wish to delete.
Deleting all points (clearing the map)
To delete all points, simply reload the application. The map view will be preserved, so you will not lose the location you are currently working on. All other settings (e.g. the GPS frequency) will however not be preserved.
The "Move point" tool can be used to manually move points around. To move a point, click on it first to select it: the point will then start following the mouse cursor. Clicking once again will release the point at its current position.
Setting latitude and longitude values for a point
The "Edit point" tool allows you to directly set the latitude and longitude values for a point. First, select a point, then you will be able to change its latitude and longitude values on the menu (left side). Pressing the "Enter" key will move the point to the new specified location. To release the point, click anywhere on the map.
Adding multiple points on a straight line
With the "Multi-point line" tool, you can draw multiple points along a line with the same distance from each other. When you click on the map, all preview points will be added to your path.
Since the time elapsed between two consecutive points is always the same, the "Multi-point line" tool represents motion along a straight line with constant velocity. The distance between consecutive points can be changed on the menu (left side), and the associated speed is shown right below it.
By default, the time elapsed between two consecutive points on the map is one second. To change this, click on "Global settings" and modify the GPS frequency value. This value defines how many positions are obtained per second, so setting it to 10Hz means the time elapsed between two consecutive points will be 100 milliseconds (0.1 seconds).
The GPS frequency is a global setting, so changing its value will affect the associated speeds at all points. As an example, increasing the GPS frequency by a factor of 10 means all speeds will be increased by a factor of 10 as well.
Generating and loading NMEA files
After drawing the desired path, you can generate a file containing a sequence of NMEA (GGA, GSA and RMC) sentences representing the path drawn. To do that, click on the "Generate NMEA file" button.
You can also load an NMEA file generated with this or another application by clicking on the "Load NMEA file" button. The path represented by this file will then be drawn automatically on the map. The positions of the points are extracted from the GGA sentences.
Downloading and loading coordinate files
After drawing the desired path, you can generate a file containing its coordinates. The file will be in CSV format, with each line containing the coordinates of a point in the path (one latitude value and one longitude value separated by a comma). To do that, click on the "Download coordinates (CSV)" button.
You can also load a CSV file containing coordinates represented in this same format by clicking the "Load coordinates (CSV)" button. The path represented by this file will then be drawn automatically on the map.
To report a bug, please send an e-mail to firstname.lastname@example.org.
Who created this marvelous tool?
The NMEA Generator was created by Diego Assencio.
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